{"id":35145,"date":"2019-10-31T22:02:32","date_gmt":"2019-10-31T19:02:32","guid":{"rendered":"https:\/\/prohoster.info\/blog\/audio-cherez-bluetooth-maksimalno-podrobno-o-profilyah-kodekah-i-ustrojstvah\/"},"modified":"2019-10-31T22:02:32","modified_gmt":"2019-10-31T19:02:32","slug":"audio-cherez-bluetooth-maksimalno-podrobno-o-profilyah-kodekah-i-ustrojstvah","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/audio-cherez-bluetooth-maksimalno-podrobno-o-profilyah-kodekah-i-ustrojstvah","title":{"rendered":"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/48eced30a8d5e569e0c70ab4d60c5a9f.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nVzhledem k masov\u00e9mu uv\u00e1d\u011bn\u00ed chytr\u00fdch telefon\u016f bez 3,5 mm audio konektoru se bezdr\u00e1tov\u00e1 Bluetooth sluch\u00e1tka stala pro mnoh\u00e9 hlavn\u00edm zp\u016fsobem poslouch\u00e1n\u00ed hudby a komunikace v re\u017eimu handsfree.<br \/>\nV\u00fdrobci bezdr\u00e1tov\u00fdch za\u0159\u00edzen\u00ed \u010dasto nep\u00ed\u0161\u00ed podrobn\u00e9 specifikace v\u00fdrobk\u016f, a \u010dl\u00e1nky o Bluetooth audiu na internetu jsou mnohdy protich\u016fdn\u00e9, m\u00edsty nekorektn\u00ed, nezmi\u0148uj\u00ed v\u0161echny vlastnosti a \u010dasto kop\u00edruj\u00ed stejnou nep\u0159esnou informaci.<br \/>\nPokud se pokus\u00edme pono\u0159it do protokolu, mo\u017enost\u00ed Bluetooth stack\u016f opera\u010dn\u00edch syst\u00e9m\u016f, sluch\u00e1tek a reproduktor\u016f, Bluetooth kodek\u016f pro hudbu a \u0159e\u010d, zjist\u00edme, co ovliv\u0148uje kvalitu p\u0159en\u00e1\u0161en\u00e9ho zvuku a zpo\u017ed\u011bn\u00ed, nau\u010d\u00edme se shroma\u017e\u010fovat a dek\u00f3dovat informace o podporovan\u00fdch kodec\u00edch a dal\u0161\u00edch mo\u017enostech za\u0159\u00edzen\u00ed.<\/p>\n<p><b>TL;DR<\/b>: <\/p>\n<ul>\n<li>SBC \u2014 b\u011b\u017en\u00fd kodek<\/li>\n<li>Sluch\u00e1tka maj\u00ed sv\u016fj ekvaliz\u00e9r a post-procesing pro ka\u017ed\u00fd kodek samostatn\u011b<\/li>\n<li>aptX nen\u00ed tak dobr\u00fd, jak tvrd\u00ed reklamn\u00ed ozn\u00e1men\u00ed<\/li>\n<li>LDAC \u2014 marketingov\u00e9 bl\u00e1boly<\/li>\n<li>Kvalita zvuku v re\u017eimu hovoru je st\u00e1le n\u00edzk\u00e1<\/li>\n<li>Do prohl\u00ed\u017ee\u010de je mo\u017en\u00e9 integrovat audio enkod\u00e9ry v C, zkompilov\u00e1n\u00edm do WebAssembly pomoc\u00ed emscripten, a nebudou zvl\u00e1\u0161\u0165 zpomalovat.<\/li>\n<\/ul>\n<p>\n<noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><\/p>\n<h1>Hudba p\u0159es Bluetooth<\/h1>\n<p>Funk\u010dn\u00ed slo\u017eka Bluetooth je ur\u010dena profily \u2014 specifikacemi konkr\u00e9tn\u00edch funkc\u00ed. P\u0159enos hudby p\u0159es Bluetooth prob\u00edh\u00e1 pomoc\u00ed profilu pro p\u0159enos vysoce kvalitn\u00edho jednosm\u011brn\u00e9ho audia A2DP. Standard A2DP byl p\u0159ijat v roce 2003 a od t\u00e9 doby se z\u00e1sadn\u011b nezm\u011bnil.<br \/>\nV r\u00e1mci profilu je standardizov\u00e1n 1 povinn\u00fd kodek s n\u00edzkou v\u00fdpo\u010detn\u00ed slo\u017eitost\u00ed SBC, vytvo\u0159en\u00fd speci\u00e1ln\u011b pro Bluetooth, a 3 dal\u0161\u00ed. Tak\u00e9 je povoleno pou\u017eit\u00ed nedokumentovan\u00fdch kodek\u016f vlastn\u00ed implementace.<\/p>\n<p>K datu \u010derven 2019 se nach\u00e1z\u00edme <noindex><a rel=\"nofollow\" href=\"https:\/\/xkcd.com\/927\/\">v komiksu xkcd<\/a><\/noindex> s 14 A2DP kodeky:<\/p>\n<ul>\n<li><b>SBC<\/b> \u2190 standardizov\u00e1no v A2DP, podporov\u00e1no v\u0161emi za\u0159\u00edzen\u00edmi<\/li>\n<li><b>MPEG-1\/2 Layer 1\/2\/3<\/b> \u2190 standardizov\u00e1ny v A2DP: v\u0161em zn\u00e1m\u00e9 <noindex><a rel=\"nofollow\" href=\"https:\/\/en.wikipedia.org\/wiki\/MP3\">MP3<\/a><\/noindex>, pou\u017e\u00edvan\u00fd v digit\u00e1ln\u00ed TV <noindex><a rel=\"nofollow\" href=\"https:\/\/en.wikipedia.org\/wiki\/MPEG-1_Audio_Layer_II\">MP2<\/a><\/noindex>, a nezn\u00e1m\u00fd <noindex><a rel=\"nofollow\" href=\"https:\/\/en.wikipedia.org\/wiki\/MPEG-1_Audio_Layer_I\">MP1<\/a><\/noindex><\/li>\n<li><b>MPEG-2\/4 AAC<\/b> \u2190 standardizov\u00e1no v A2DP<\/li>\n<li><b>ATRAC<\/b> \u2190 star\u00fd kodek od Sony, standardizovan\u00fd v A2DP<\/li>\n<li><b>LDAC<\/b> \u2190 nov\u00fd kodek od Sony<\/li>\n<li><b>aptX<\/b> \u2190 kodek z roku 1988<\/li>\n<li><b>aptX HD<\/b> \u2190 to sam\u00e9 co aptX, pouze s jin\u00fdmi parametry k\u00f3dov\u00e1n\u00ed<\/li>\n<li><b>aptX Low Latency<\/b> \u2190 zcela jin\u00fd kodek, nen\u00ed softwarov\u00e1 implementace<\/li>\n<li><b>aptX Adaptive<\/b> \u2190 dal\u0161\u00ed kodek od Qualcomm<\/li>\n<li><b>FastStream<\/b> \u2190 pseudokodek, obousm\u011brn\u00e1 modifikace SBC<\/li>\n<li><b>HWA LHDC<\/b> \u2190 nov\u00fd kodek od Huawei<\/li>\n<li><b>Samsung HD<\/b> \u2190 podporov\u00e1no 2 za\u0159\u00edzen\u00edmi<\/li>\n<li><b>Samsung Scalable<\/b> \u2190 podporov\u00e1no 2 za\u0159\u00edzen\u00edmi<\/li>\n<li><b>Samsung UHQ-BT<\/b> \u2190 podporov\u00e1no 3 za\u0159\u00edzen\u00edmi<\/li>\n<\/ul>\n<p>Pro\u010d vlastn\u011b pot\u0159ebujeme kodeky, pt\u00e1te se, kdy\u017e je v Bluetooth EDR, kter\u00e9 umo\u017e\u0148uje p\u0159enos dat rychlost\u00ed 2 a 3 Mbit\/s, a pro nekomprimovan\u00fd dvoukan\u00e1lov\u00fd 16bitov\u00fd PCM sta\u010d\u00ed 1,4 Mbit\/s?<\/p>\n<p><\/p>\n<h1>P\u0159enos dat p\u0159es Bluetooth<\/h1>\n<p>V Bluetooth existuj\u00ed dva typy p\u0159enosu dat: Asynchronous Connection Less (ACL) pro asynchronn\u00ed p\u0159enos bez nav\u00e1z\u00e1n\u00ed spojen\u00ed a Synchronous Connection Oriented (SCO) pro synchronn\u00ed p\u0159enos s p\u0159edchoz\u00edm schv\u00e1len\u00edm spojen\u00ed.<br \/>\nP\u0159enos prob\u00edh\u00e1 pomoc\u00ed \u010dasov\u00e9ho d\u011blen\u00ed a volby p\u0159enosov\u00e9ho kan\u00e1lu pro ka\u017ed\u00fd paket zvl\u00e1\u0161\u0165 (Frequency-Hop\/Time-Division-Duplex, FH\/TDD), p\u0159i\u010dem\u017e \u010das je rozd\u011blen na intervaly po 625 mikrosekund\u00e1ch, naz\u00fdvan\u00e9 sloty. Jedno za\u0159\u00edzen\u00ed prov\u00e1d\u00ed p\u0159enos v sud\u00fdch slotech, druh\u00e9 \u2014 v lich\u00fdch. P\u0159en\u00e1\u0161en\u00fd paket m\u016f\u017ee zab\u00edrat 1, 3 nebo 5 slot\u016f v z\u00e1vislosti na velikosti dat a nastaven\u00e9m typu p\u0159enosu, p\u0159i\u010dem\u017e v tomto p\u0159\u00edpad\u011b nen\u00ed jedno za\u0159\u00edzen\u00ed v sud\u00fdch a lich\u00fdch slotech b\u011bhem p\u0159enosu. Celkem je v sekund\u011b mo\u017en\u00e9 p\u0159ijmout a odeslat a\u017e 1600 paket\u016f, pokud ka\u017ed\u00fd z nich zab\u00edr\u00e1 1 slot, a ob\u011b za\u0159\u00edzen\u00ed neust\u00e1le n\u011bco p\u0159en\u00e1\u0161ej\u00ed a p\u0159ij\u00edmaj\u00ed.<\/p>\n<p>2 a 3 Mbit\/s pro EDR, kter\u00e9 m\u016f\u017eete naj\u00edt v ozn\u00e1men\u00edch a na webov\u00fdch str\u00e1nk\u00e1ch Bluetooth, p\u0159edstavuj\u00ed maxim\u00e1ln\u00ed kan\u00e1lovou rychlost p\u0159enosu v\u0161ech dat dohromady (v\u010detn\u011b technick\u00fdch z\u00e1hlav\u00ed v\u0161ech protokol\u016f, do nich\u017e je t\u0159eba data zabalit) ve dvou sm\u011brech sou\u010dasn\u011b. Skute\u010dn\u00e1 rychlost p\u0159enosu dat se bude v\u00fdrazn\u011b li\u0161it.<\/p>\n<p>Pro p\u0159enos hudby se pou\u017e\u00edv\u00e1 asynchronn\u00ed zp\u016fsob, t\u00e9m\u011b\u0159 v\u017edy pomoc\u00ed paket\u016f typu 2-DH5 a 3-DH5, kter\u00e9 nesou maxim\u00e1ln\u00ed mno\u017estv\u00ed dat v re\u017eimu EDR 2 Mbit\/s a 3 Mbit\/s, a zab\u00edraj\u00ed 5 slot\u016f \u010dasov\u00e9ho d\u011blen\u00ed p\u00e1sma.<\/p>\n<p>Sch\u00e9matick\u00e9 zn\u00e1zorn\u011bn\u00ed p\u0159enosu s pou\u017eit\u00edm 5 slot\u016f jedn\u00edm za\u0159\u00edzen\u00edm a 1 slotu druh\u00fdm (DH5\/DH1):<br \/>\n<img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/e5875cb59648c349a63c8e7196e9afbf.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nD\u00edky principu \u010dasov\u00e9ho rozd\u011blen\u00ed mus\u00ed p\u0159i p\u0159enosu paketu \u010dekat 625 mikrosekundov\u00fd \u010dasov\u00fd slot, pokud n\u00e1m druh\u00e9 za\u0159\u00edzen\u00ed nic nep\u0159en\u00e1\u0161\u00ed nebo p\u0159en\u00e1\u0161\u00ed mal\u00fd paket, a del\u0161\u00ed dobu, pokud druh\u00e9 za\u0159\u00edzen\u00ed p\u0159en\u00e1\u0161\u00ed v\u011bt\u0161\u00ed pakety. Pokud je k telefonu p\u0159ipojeno v\u00edce ne\u017e jedno za\u0159\u00edzen\u00ed (nap\u0159\u00edklad sluch\u00e1tka, hodinky a fitness n\u00e1ramek), doba p\u0159enosu se d\u011bl\u00ed mezi v\u0161echny.<\/p>\n<p>Nutnost zapouzd\u0159en\u00ed audia do speci\u00e1ln\u00edch transportn\u00edch protokol\u016f L2CAP a AVDTP od\u010derp\u00e1v\u00e1 16 bajt\u016f z maxim\u00e1ln\u00ed mo\u017en\u00e9 p\u0159enosov\u00e9 u\u017eite\u010dn\u00e9 audio z\u00e1t\u011b\u017ee.<\/p>\n<p>Typ paketu<br \/>\nPo\u010det slot\u016f<br \/>\nMax. po\u010det bajt\u016f v paketu<br \/>\nMax. po\u010det bajt\u016f u\u017eite\u010dn\u00e9 z\u00e1t\u011b\u017ee A2DP<br \/>\nMax. bitrate u\u017eite\u010dn\u00e9 z\u00e1t\u011b\u017ee A2DP<\/p>\n<p>2-DH3<br \/>\n3<br \/>\n367<br \/>\n351<br \/>\n936 kbit\/s<\/p>\n<p>3-DH3<br \/>\n3<br \/>\n552<br \/>\n536<br \/>\n1429 kbit\/s<\/p>\n<p>2-DH5<br \/>\n5<br \/>\n679<br \/>\n663<br \/>\n1414 kbit\/s<\/p>\n<p>3-DH5<br \/>\n5<br \/>\n1021<br \/>\n1005<br \/>\n2143 kbit\/s<\/p>\n<p>1414 a 1429 kbit\/s rozhodn\u011b nesta\u010d\u00ed pro p\u0159enos nekomprimovan\u00e9ho zvuku za skute\u010dn\u00fdch podm\u00ednek s ru\u0161en\u00fdm p\u00e1smem 2.4 GHz a nutnost\u00ed p\u0159enosu \u0159\u00edd\u00edc\u00edch dat. EDR s 3 Mbit\/s vy\u017eaduje vysok\u00fd v\u00fdkon p\u0159enosu a \u0161um v \u00e9teru, proto ani v re\u017eimu 3-DH5 nen\u00ed pohodln\u00fd p\u0159enos PCM mo\u017en\u00fd, neust\u00e1le dojde k kr\u00e1tk\u00fdm p\u0159eru\u0161en\u00edm a v\u0161e bude fungovat pouze na vzd\u00e1lenosti n\u011bkolika metr\u016f.<br \/>\nV praxi je obt\u00ed\u017en\u00e9 p\u0159en\u00e1\u0161et dokonce i audio stream 990 kbit\/s (LDAC 990 kbit\/s).<\/p>\n<p>Vr\u00e1t\u00edme se k kodek\u016fm.<\/p>\n<h2>SBC<\/h2>\n<p>Kodek, kter\u00fd je povinn\u00fd pro v\u0161echna za\u0159\u00edzen\u00ed podporuj\u00edc\u00ed standard A2DP. Nejlep\u0161\u00ed a nejhor\u0161\u00ed kodek z\u00e1rove\u0148.<\/p>\n<p>Vzorkovac\u00ed frekvence<br \/>\n\u0160\u00ed\u0159ka slova<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p>16, 32, 44.1, 48 kHz<br \/>\n16 bit\u016f<br \/>\n10-1500 kbit\/s<br \/>\nV\u0161emi za\u0159\u00edzen\u00edmi<br \/>\nV\u0161emi za\u0159\u00edzen\u00edmi<\/p>\n<p>SBC je jednoduch\u00fd a v\u00fdpo\u010detn\u011b rychl\u00fd kodek s primitivn\u00edm psychoakustick\u00fdm modelem (pou\u017e\u00edv\u00e1 se pouze maskov\u00e1n\u00ed tich\u00fdch zvuk\u016f), kter\u00fd pou\u017e\u00edv\u00e1 adaptivn\u00ed impulsn\u011b-k\u00f3dovou modulaci (APCM).<br \/>\nSpecifikace A2DP doporu\u010duje pou\u017eit\u00ed dvou profil\u016f: St\u0159edn\u00ed kvalita a Vysok\u00e1 kvalita.<br \/>\n<img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/8939e552a23374228289a9686f4d1048.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nKodek m\u00e1 mnoho nastaven\u00ed, kter\u00e1 umo\u017e\u0148uj\u00ed ovl\u00e1dat algoritmickou latenci, po\u010det vzork\u016f v bloku, algoritmus p\u0159id\u011blov\u00e1n\u00ed bit\u016f, ale t\u00e9m\u011b\u0159 v\u0161ude se pou\u017e\u00edvaj\u00ed stejn\u00e9 doporu\u010den\u00e9 parametry ve specifikaci: Joint Stereo, 8 frekven\u010dn\u00edch p\u00e1sem, 16 blok\u016f v audio r\u00e1mci, zp\u016fsob p\u0159id\u011blov\u00e1n\u00ed bit\u016f Loudness.<br \/>\nSBC podporuje dynamickou zm\u011bnu parametru Bitpool, kter\u00fd p\u0159\u00edmo ovliv\u0148uje bitrate. Pokud je r\u00e1diov\u00fd sign\u00e1l p\u0159et\u00ed\u017een, ztr\u00e1c\u00ed se pakety nebo jsou za\u0159\u00edzen\u00ed na velkou vzd\u00e1lenost, m\u016f\u017ee zdroj audia sn\u00ed\u017eit Bitpool, dokud se spojen\u00ed nevr\u00e1t\u00ed do norm\u00e1lu.<\/p>\n<p>V\u011bt\u0161ina v\u00fdrobc\u016f sluch\u00e1tek nastavuje maxim\u00e1ln\u00ed hodnotu parametru Bitpool na 53, co\u017e omezuje bitrate na 328 kilobit\u016f za sekundu p\u0159i pou\u017eit\u00ed doporu\u010den\u00e9ho profilu.<br \/>\nI kdy\u017e v\u00fdrobce sluch\u00e1tek nastavil maxim\u00e1ln\u00ed hodnotu Bitpoolu na v\u00edce ne\u017e 53 (takov\u00e9 modely se objevuj\u00ed nap\u0159\u00edklad: Beats Solo\u00b3, JBL Everest Elite 750NC, Apple AirPods, tak\u00e9 se vyskytuj\u00ed u n\u011bkter\u00fdch p\u0159ij\u00edma\u010d\u016f a automobilov\u00fdch hlavn\u00edch jednotek), v\u011bt\u0161ina opera\u010dn\u00edch syst\u00e9m\u016f neumo\u017en\u00ed pou\u017e\u00edvat zv\u00fd\u0161en\u00e9 bitrate kv\u016fli intern\u00edmu omezen\u00ed hodnoty v Bluetooth stacku.<br \/>\nKrom\u011b toho n\u011bkte\u0159\u00ed v\u00fdrobci nastavuj\u00ed n\u00edzkou maxim\u00e1ln\u00ed hodnotu Bitpoolu pro n\u011bkter\u00e1 za\u0159\u00edzen\u00ed. Nap\u0159\u00edklad u Bluedio T je to 39, u Samsung Gear IconX \u2014 37, co\u017e poskytuje \u0161patnou kvalitu zvuku.<\/p>\n<p>Um\u011bl\u00e1 omezen\u00ed ze strany v\u00fdvoj\u00e1\u0159\u016f Bluetooth stack\u016f pravd\u011bpodobn\u011b vznikla v d\u016fsledku nekompatibility n\u011bkter\u00fdch za\u0159\u00edzen\u00ed s vysok\u00fdmi hodnotami Bitpoolu nebo netypick\u00fdmi profily, i kdy\u017e hl\u00e1sila jejich podporu, a nedostate\u010dn\u00e9ho po\u010dtu test\u016f p\u0159i certifikaci. Autor\u016fm Bluetooth stack\u016f bylo snaz\u0161\u00ed se omezit na dodr\u017eov\u00e1n\u00ed doporu\u010den\u00e9ho profilu, ne\u017e vytv\u00e1\u0159et datab\u00e1zi nespr\u00e1vn\u00fdch za\u0159\u00edzen\u00ed (i kdy\u017e te\u010f to d\u011blaj\u00ed pro dal\u0161\u00ed nespr\u00e1vn\u011b funguj\u00edc\u00ed funkce).<\/p>\n<p>SBC dynamicky p\u0159i\u0159azuje kvantiza\u010dn\u00ed bity pro frekven\u010dn\u00ed p\u00e1sma, p\u0159i\u010dem\u017e postupuje od ni\u017e\u0161\u00edch k vy\u0161\u0161\u00edm s r\u016fzn\u00fdmi v\u00e1hami. Pokud je cel\u00fd bitrate pou\u017eit na ni\u017e\u0161\u00ed a st\u0159edn\u00ed frekvence, vy\u0161\u0161\u00ed frekvence budou \u201eo\u0159ez\u00e1ny\u201c (m\u00edsto nich bude ticho).<\/p>\n<p>P\u0159\u00edklad SBC 328 kbit\/s. Vlevo \u2014 origin\u00e1l, vpravo \u2014 SBC, periodicky doch\u00e1z\u00ed k p\u0159ep\u00edn\u00e1n\u00ed mezi stopami. Pro audio ve video souboru se pou\u017e\u00edv\u00e1 bezztr\u00e1tov\u00fd kompresn\u00ed kodek FLAC. Pou\u017eit\u00ed FLAC v kontejneru mp4 nen\u00ed ofici\u00e1ln\u011b standardizov\u00e1no, tak\u017ee nen\u00ed jist\u00e9, \u017ee v\u00e1\u0161 prohl\u00ed\u017ee\u010d jej p\u0159ehraje, ale m\u011blo by to fungovat v posledn\u00edch verz\u00edch desktopov\u00fdch Chrome a Firefox. Pokud nem\u00e1te zvuk, m\u016f\u017eete si soubor st\u00e1hnout a otev\u0159\u00edt jej v plnohodnotn\u00e9m video p\u0159ehr\u00e1va\u010di.<br \/>\n<video controls style=\"top: 0; left: 0; width: 100%; height: 100%; position: absolute;\">V\u00e1\u0161 prohl\u00ed\u017ee\u010d nepodporuje HTML5 video.<source src=\"https:\/\/files.catbox.moe\/8yrssu.mp4\" type=\"video\/mp4\"><\/source><\/video><i>ZZ Top \u2014 Sharp Dressed Man<\/i><\/p>\n<p>Na spektr\u00e1ln\u00ed anal\u00fdze je vid\u011bt okam\u017eik p\u0159epnut\u00ed: SBC pravideln\u011b p\u0159et\u00edn\u00e1 tich\u00fdch zvuk\u016f nad 17,5 kHz a v\u016fbec nevy\u010dle\u0148uje bity pro p\u00e1smo nad 20 kHz. \u00dapln\u00e1 spektr\u00e1ln\u00ed anal\u00fdza je k dispozici po kliknut\u00ed (1,7 MB).<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/qj\/i7\/4w\/qji74wrphaigw3qtza6nepvur50.png\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/c59aa3f6eff4c4d966a4c96868dd7e00.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p>Nesly\u0161\u00edm rozd\u00edl mezi origin\u00e1lem a SBC na t\u00e9to stop\u011b.<\/p>\n<p>Vezm\u011bme n\u011bco nov\u011bj\u0161\u00edho a modelujme audio, kter\u00e9 by vzniklo p\u0159i pou\u017eit\u00ed sluch\u00e1tek Samsung Gear IconX s Bitpool 37 (naho\u0159e \u2014 p\u016fvodn\u00ed sign\u00e1l, dole \u2014 SBC 239 kbps, zvuk ve FLAC).<br \/>\n<video controls style=\"top: 0; left: 0; width: 100%; height: 100%; position: absolute;\">V\u00e1\u0161 prohl\u00ed\u017ee\u010d nepodporuje HTML5 video.<source src=\"https:\/\/files.catbox.moe\/r561g5.mp4\" type=\"video\/mp4\"><\/source><\/video><i>Mindless Self Indulgence \u2014 Witness<\/i><\/p>\n<p>Sly\u0161\u00edm prask\u00e1n\u00ed, men\u0161\u00ed stereoefekt a nep\u0159\u00edjemn\u00e9 \"cvak\u00e1n\u00ed\" vok\u00e1lu ve vysok\u00fdch frekvenc\u00edch.<\/p>\n<p>A\u010dkoli je SBC velmi flexibiln\u00ed kodek a m\u016f\u017ee b\u00fdt nastaven na n\u00edzk\u00e9 latence, poskytuje vynikaj\u00edc\u00ed kvalitu audia p\u0159i vysok\u00fdch bitrates (452+ kbps) a celkem dobrou pro v\u011bt\u0161inu lid\u00ed na standardn\u00edm High Quality (328 kbps), proto\u017ee standard A2DP nenastavuje pevn\u00e9 profily (ale poskytuje pouze doporu\u010den\u00ed), v\u00fdvoj\u00e1\u0159i stack\u016f nastavili um\u011bl\u00e1 omezen\u00ed na Bitpool, parametry p\u0159en\u00e1\u0161en\u00e9ho audia se nezobrazuj\u00ed v u\u017eivatelsk\u00e9m rozhran\u00ed, a v\u00fdrobci sluch\u00e1tek maj\u00ed volnost nastavit sv\u00e9 parametry a nikdy neuv\u00e1d\u011bj\u00ed hodnotu Bitpool v technick\u00fdch specifikac\u00edch produktu, kodek se proslavil n\u00edzkou kvalitou zvuku, co\u017e v\u0161ak nen\u00ed probl\u00e9m samotn\u00e9ho kodeku.<br \/>\nParametr Bitpool p\u0159\u00edmo ovliv\u0148uje bitrate pouze v r\u00e1mci jednoho profilu. Stejn\u00e9 hodnoty Bitpool 53 mohou p\u0159in\u00e1\u0161et bitrate 328 kbps p\u0159i doporu\u010den\u00e9m profilu High Quality, stejn\u011b jako 1212 kbps s Dual Channel a 4 frekven\u010dn\u00edmi p\u00e1smy, co\u017e je d\u016fvod, pro\u010d auto\u0159i OS, krom\u011b omezen\u00ed na Bitpool, nastavuj\u00ed omezen\u00ed tak\u00e9 na Bitrate. Jak se domn\u00edv\u00e1m, tato situace vznikla kv\u016fli nedostatku standardu A2DP: m\u011blo se koordinovat bitrate, a ne Bitpool.<\/p>\n<p>Tabulka podpory mo\u017enost\u00ed SBC v r\u016fzn\u00fdch opera\u010dn\u00edch syst\u00e9mech:<\/p>\n<p>OS<br \/>\nPodporovan\u00e9 vzorkovac\u00ed frekvence<br \/>\nOmezen\u00ed max. Bitpool<br \/>\nOmezen\u00ed max. Bitrate<br \/>\nTypick\u00fd Bitrate<br \/>\nDynamick\u00e9 nastaven\u00ed Bitpool<\/p>\n<p><b>Windows 10<\/b><br \/>\n44,1 kHz<br \/>\n53<br \/>\n512 kbps<br \/>\n328 kbps<br \/>\n\u2713*<\/p>\n<p><b>Linux (BlueZ + PulseAudio)<\/b><br \/>\n16, 32, 44.1, 48 kHz<br \/>\n64 (p\u0159i p\u0159\u00edchoz\u00edm p\u0159ipojen\u00ed), 53 (p\u0159i odchoz\u00edm)<br \/>\n\u017d\u00e1dn\u00e9 omezen\u00ed<br \/>\n328 kbps<br \/>\n\u2713*<\/p>\n<p><b>macOS High Sierra<\/b><br \/>\n44,1 kHz<br \/>\n64, defaultn\u011b 53***<br \/>\nNezn\u00e1m\u00e9<br \/>\n328 kbps<br \/>\n\u2717<\/p>\n<p><b>Android 4.4-9<\/b><br \/>\n44,1\/48 kHz**<br \/>\n53<br \/>\n328 kbps<br \/>\n328 kbps<br \/>\n\u2717<\/p>\n<p><b>Android 4.1-4.3.1<\/b><br \/>\n44,1, 48 kHz**<br \/>\n53<br \/>\n229 kbps<br \/>\n229 kbps<br \/>\n\u2717<\/p>\n<p><b>Blackberry OS 10<\/b><br \/>\n48 kHz<br \/>\n53<br \/>\n\u017d\u00e1dn\u00e9 omezen\u00ed<br \/>\n328 kbps<br \/>\n\u2717<\/p>\n<p><i><b>*<\/b> Bitpool se pouze zmen\u0161uje, ale nezv\u011bt\u0161uje automaticky, pokud se zlep\u0161\u00ed podm\u00ednky p\u0159enosu. Pro obnoven\u00ed Bitpoolu je t\u0159eba zastavit p\u0159ehr\u00e1v\u00e1n\u00ed, po\u010dkat n\u011bkolik sekund a znovu spustit audio.<br \/>\n<b>**<\/b> V\u00fdchoz\u00ed hodnota z\u00e1vis\u00ed na nastaven\u00edch z\u00e1sobn\u00edku, kter\u00e9 byly uvedeny p\u0159i kompilaci firmwaru. V Androidu 8\/8.1 je frekvence pouze 44,1 kHz nebo 48 kHz v z\u00e1vislosti na nastaven\u00ed p\u0159i kompilaci, v ostatn\u00edch verz\u00edch jsou podporov\u00e1ny 44,1 kHz a 48 kHz sou\u010dasn\u011b.<br \/>\n<b>***<\/b> Hodnotu Bitpool lze zv\u00fd\u0161it v programu Bluetooth Explorer.<\/i><\/p>\n<h2>aptX a aptX HD<\/h2>\n<p>aptX je jednoduch\u00fd a v\u00fdpo\u010detn\u011b rychl\u00fd kodek, bez psychoakustiky, kter\u00fd pou\u017e\u00edv\u00e1 adaptivn\u00ed diferenci\u00e1ln\u00ed impulzn\u011b k\u00f3dovou modulaci (<noindex><a rel=\"nofollow\" href=\"https:\/\/ru.wikipedia.org\/wiki\/%D0%90%D0%B4%D0%B0%D0%BF%D1%82%D0%B8%D0%B2%D0%BD%D0%B0%D1%8F_%D0%B4%D0%B8%D1%84%D1%84%D0%B5%D1%80%D0%B5%D0%BD%D1%86%D0%B8%D0%B0%D0%BB%D1%8C%D0%BD%D0%B0%D1%8F_%D0%B8%D0%BC%D0%BF%D1%83%D0%BB%D1%8C%D1%81%D0%BD%D0%BE-%D0%BA%D0%BE%D0%B4%D0%BE%D0%B2%D0%B0%D1%8F_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D1%8F%D1%86%D0%B8%D1%8F\">ADPCM<\/a><\/noindex>). Objevil se p\u0159ibli\u017en\u011b v roce 1988 (datum pod\u00e1n\u00ed <noindex><a rel=\"nofollow\" href=\"https:\/\/patents.google.com\/patent\/EP0398973B1\/en\">patentu<\/a><\/noindex> je datov\u00e1no na \u00fanor 1988), p\u0159ed Bluetooth byl pou\u017e\u00edv\u00e1n p\u0159ev\u00e1\u017en\u011b v profesion\u00e1ln\u00edm bezdr\u00e1tov\u00e9m audio za\u0159\u00edzen\u00ed. V sou\u010dasnosti pat\u0159\u00ed spole\u010dnosti Qualcomm, vy\u017eaduje licencov\u00e1n\u00ed a licen\u010dn\u00ed poplatky. K 2014: $6000 jednor\u00e1zov\u011b a p\u0159ibli\u017en\u011b $1 za ka\u017ed\u00e9 za\u0159\u00edzen\u00ed, pro \u0161ar\u017ee do 10000 za\u0159\u00edzen\u00ed (<noindex><a rel=\"nofollow\" href=\"https:\/\/www.silabs.com\/documents\/login\/presentations\/Developing-Bluetooth-Audio.pdf\">zdroj<\/a><\/noindex>, str. 16).<br \/>\naptX a aptX HD jsou stejn\u00fd kodek, s r\u016fzn\u00fdmi profily k\u00f3dov\u00e1n\u00ed.<\/p>\n<p>Kodek m\u00e1 pouze jeden parametr \u2014 v\u00fdb\u011br vzorkovac\u00ed frekvence. Je pravda, \u017ee existuje tak\u00e9 v\u00fdb\u011br po\u010dtu\/re\u017eimu kan\u00e1l\u016f, ale ve v\u0161ech mn\u011b zn\u00e1m\u00fdch za\u0159\u00edzen\u00edch (70+ kus\u016f) je podpora pouze pro Stereo.<\/p>\n<p>Kodek<br \/>\nVzorkovac\u00ed frekvence<br \/>\n\u0160\u00ed\u0159ka slova<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p><b>aptX<\/b><br \/>\n16, 32, 44.1, 48 kHz<br \/>\n16 bit\u016f<br \/>\n128 \/ 256 \/ 352 \/ 384 kbit\/s (v z\u00e1vislosti na vzorkovac\u00ed frekvenci)<br \/>\nWindows 10 (desktopov\u00e1 a mobiln\u00ed), macOS, Android 4.4+\/7*, Blackberry OS 10<br \/>\n\u0160irok\u00fd v\u00fdb\u011br audio za\u0159\u00edzen\u00ed (hardwarov\u011b)<\/p>\n<p><i><b>*<\/b> Verze do 7 vy\u017eaduj\u00ed modifikaci Bluetooth z\u00e1sobn\u00edku. Kodek je podporov\u00e1n pouze tehdy, pokud v\u00fdrobce Android za\u0159\u00edzen\u00ed licencoval jeho pou\u017e\u00edv\u00e1n\u00ed od Qualcomm (pokud m\u00e1 OS knihovny pro k\u00f3dov\u00e1n\u00ed).<\/i><\/p>\n<p>aptX rozd\u011bluje audio na 4 frekven\u010dn\u00ed p\u00e1sma a kvantuje je stejn\u00fdm po\u010dtem bit\u016f neust\u00e1le: 8 bit\u016f pro 0-5,5 kHz, 4 bity pro 5,5-11 kHz, 2 bity pro 11-16,5 kHz, 2 bity pro 16,5-22 kHz (\u010d\u00edsla pro vzorkovac\u00ed frekvenci 44,1 kHz).<\/p>\n<p>P\u0159\u00edklad aptX audio (naho\u0159e je p\u016fvodn\u00ed sign\u00e1l, dole je aptX, spektrum pouze lev\u00fdch kan\u00e1l\u016f, zvuk ve FLAC):<br \/>\n<video controls style=\"top: 0; left: 0; width: 100%; height: 100%; position: absolute;\">V\u00e1\u0161 prohl\u00ed\u017ee\u010d nepodporuje HTML5 video.<source src=\"https:\/\/files.catbox.moe\/06eohy.mp4\" type=\"video\/mp4\"><\/source><\/video><br \/>\nVysok\u00e9 frekvence se trochu z\u010dervenaly, ale rozd\u00edl nen\u00ed sly\u0161iteln\u00fd.<\/p>\n<p>Vzhledem k pevn\u00e9mu rozd\u011blen\u00ed bit\u016f kvantizace nem\u016f\u017ee kodek \"p\u0159en\u00e9st bity\" na frekvence, kter\u00e9 jich nejv\u00edce pot\u0159ebuj\u00ed. Na rozd\u00edl od SBC, aptX nebude \"\u0159ezat\" frekvence, ale bude k nim p\u0159id\u00e1vat kvantiza\u010dn\u00ed \u0161um, \u010d\u00edm\u017e se sn\u00ed\u017e\u00ed dynamick\u00fd rozsah zvuku.<\/p>\n<p>Nen\u00ed t\u0159eba p\u0159edpokl\u00e1dat, \u017ee pou\u017eit\u00ed nap\u0159\u00edklad 2 bity pro p\u00e1smo sn\u00ed\u017e\u00ed dynamick\u00fd rozsah na 12 dB: ADPCM umo\u017e\u0148uje vyu\u017e\u00edt a\u017e 96 dB dynamick\u00e9ho rozsahu i p\u0159i pou\u017eit\u00ed 2 bit\u016f kvantizace, ale pouze p\u0159i ur\u010dit\u00e9m sign\u00e1lu.<br \/>\nADPCM ukl\u00e1d\u00e1 rozd\u00edl \u010d\u00edseln\u00e9ho zn\u00e1zorn\u011bn\u00ed mezi sou\u010dasn\u00fdm a n\u00e1sleduj\u00edc\u00edm vzorkem, m\u00edsto aby zaznamen\u00e1val absolutn\u00ed hodnotu, jako v PCM. To umo\u017e\u0148uje sn\u00ed\u017eit po\u017eadavky na mno\u017estv\u00ed bit\u016f pot\u0159ebn\u00fdch k ulo\u017een\u00ed takov\u00e9 (bezeztr\u00e1tov\u00e9) informace nebo prakticky takov\u00e9 (s relativn\u011b malou chybou zaokroulen\u00ed). Pro sn\u00ed\u017een\u00ed chyb zaokroulen\u00ed se pou\u017e\u00edvaj\u00ed tabulky koeficient\u016f.<br \/>\nP\u0159i vytv\u00e1\u0159en\u00ed kodeku auto\u0159i po\u010d\u00edtali koeficienty ADPCM na z\u00e1klad\u011b souboru hudebn\u00edch audio soubor\u016f. \u010c\u00edm bl\u00ed\u017ee je zvukov\u00fd sign\u00e1l tomuto souboru hudby, na kter\u00fdch byly tabulky postaveny, t\u00edm m\u00e9n\u011b kvantiza\u010dn\u00edch chyb (\u0161umu) aptX vytv\u00e1\u0159\u00ed.<\/p>\n<p>Z tohoto d\u016fvodu budou syntetick\u00e9 testy v\u017edy vykazovat hor\u0161\u00ed v\u00fdsledky ne\u017e hudba. Vytvo\u0159il jsem speci\u00e1ln\u00ed syntetick\u00fd p\u0159\u00edklad, na kter\u00e9m aptX ukazuje \u0161patn\u00e9 v\u00fdsledky \u2014 sinusoidu s frekvenc\u00ed 12,4 kHz (naho\u0159e \u2014 p\u016fvodn\u00ed sign\u00e1l, dole \u2014 aptX. Zvuk ve FLAC. Sni\u017ete hlasitost!):<br \/>\n<video controls style=\"top: 0; left: 0; width: 100%; height: 100%; position: absolute;\">V\u00e1\u0161 prohl\u00ed\u017ee\u010d nepodporuje HTML5 video.<source src=\"https:\/\/files.catbox.moe\/kterhd.mp4\" type=\"video\/mp4\"><\/source><\/video><br \/>\nGraf spektra:<br \/>\n<img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/94ecbf4a6f93b6ca85ca997e2be453ad.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\n\u0160umy jsou jasn\u011b sly\u0161iteln\u00e9.<\/p>\n<p>Pokud v\u0161ak vygenerujeme sinusoidu s men\u0161\u00ed amplitudou, aby byla ti\u0161\u0161\u00ed, \u0161umy se tak\u00e9 zti\u0161\u00ed, co\u017e nazna\u010duje \u0161irok\u00fd dynamick\u00fd rozsah:<\/p>\n<p><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/64d0a3f41c152f5f4d01230722fc197a.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nChcete-li sly\u0161et rozd\u00edl mezi origin\u00e1ln\u00edm hudebn\u00edm skladbou a komprimovanou verz\u00ed, m\u016f\u017eete invertovat jeden ze sign\u00e1l\u016f a zkombinovat stopy kan\u00e1l po kan\u00e1le. Tento p\u0159\u00edstup je obecn\u011b nespr\u00e1vn\u00fd a ned\u00e1val by rozumn\u00e9 v\u00fdsledky s slo\u017eit\u011bj\u0161\u00edmi kodeky, ale konkr\u00e9tn\u011b pro ADPCM je zcela vhodn\u00fd.<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/files.catbox.moe\/leq24q.flac\">Rozd\u00edl mezi origin\u00e1lem a aptX<\/a><\/noindex><br \/>\nSt\u0159edn\u00ed \u010dtvercov\u00e1 odchylka sign\u00e1l\u016f je na \u00farovni -37,4 dB, co\u017e nen\u00ed mnoho pro takto komprimovanou hudbu.<\/p>\n<h3>aptX HD<\/h3>\n<p>aptX HD nen\u00ed samostatn\u00fdm kodekem \u2014 je to vylep\u0161en\u00fd profil k\u00f3dov\u00e1n\u00ed kodeku aptX. Zm\u011bny se t\u00fdkaj\u00ed po\u010dtu bit\u016f p\u0159id\u011blen\u00fdch k\u00f3dov\u00e1n\u00ed frekven\u010dn\u00edch rozsah\u016f: 10 bit\u016f pro 0-5.5 kHz, 6 bit\u016f pro 5.5-11 kHz, 4 bity pro 11-16.5 kHz, 4 bity pro 16.5-22 kHz (\u010d\u00edsla pro 44.1 kHz).<\/p>\n<p>Kodek<br \/>\nVzorkovac\u00ed frekvence<br \/>\n\u0160\u00ed\u0159ka slova<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p><b>aptX HD<\/b><br \/>\n16, 32, 44.1, 48 kHz<br \/>\n24 bit\u016f<br \/>\n192 \/ 384 \/ 529 \/ 576 kbit\/s (v z\u00e1vislosti na vzorkovac\u00ed frekvenci)<br \/>\nAndroid 8+*<br \/>\nN\u011bkter\u00fdmi audio za\u0159\u00edzen\u00edmi (hardwarov\u011b)<\/p>\n<p><i><b>*<\/b> Verze do 7 vy\u017eaduj\u00ed modifikaci Bluetooth z\u00e1sobn\u00edku. Kodek je podporov\u00e1n pouze tehdy, pokud v\u00fdrobce Android za\u0159\u00edzen\u00ed licencoval jeho pou\u017e\u00edv\u00e1n\u00ed od Qualcomm (pokud m\u00e1 OS knihovny pro k\u00f3dov\u00e1n\u00ed).<\/i><\/p>\n<p>M\u00e9n\u011b roz\u0161\u00ed\u0159en\u00fd ne\u017e aptX: z\u0159ejm\u011b vy\u017eaduje samostatnou licenci od Qualcommu a individu\u00e1ln\u00ed licen\u010dn\u00ed poplatky.<\/p>\n<p>Opakujme p\u0159\u00edklad se sinusoidou na 12.4 kHz:<br \/>\n<img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/fe4f8d91dcbc39af881129a9c78ca453.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nMnohem lep\u0161\u00ed ne\u017e s aptX, ale st\u00e1le \u0161um\u00ed.<\/p>\n<h2>aptX Low Latency<\/h2>\n<p>Kodek od Qualcommu, kter\u00fd nem\u00e1 spole\u010dn\u00e9ho nic se standardn\u00edmi aptX a aptX HD, soud\u011b podle m\u00e1lo informac\u00ed od lid\u00ed zapojen\u00fdch do jeho v\u00fdvoje. Je ur\u010den pro interaktivn\u00ed p\u0159enos audia s n\u00edzkou latenc\u00ed (filmy, hry), kde nen\u00ed mo\u017en\u00e9 upravit zpo\u017ed\u011bn\u00ed zvuku programov\u011b. Zn\u00e1m\u00e9 softwarov\u00e9 implementace enkod\u00e9r\u016f a dekod\u00e9r\u016f neexistuj\u00ed, podporov\u00e1n je v\u00fdhradn\u011b vys\u00edla\u010di, p\u0159ij\u00edma\u010di, sluch\u00e1tky a reproduktory, nikoli smartphony a po\u010d\u00edta\u010di.<\/p>\n<p>Vzorkovac\u00ed frekvence<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p>44,1 kHz<br \/>\n276\/420 kbit\/s<br \/>\nN\u011bkter\u00fdmi vys\u00edla\u010di (hardwarov\u011b)<br \/>\nN\u011bkter\u00fdmi audio za\u0159\u00edzen\u00edmi (hardwarov\u011b)<\/p>\n<h2>AAC<\/h2>\n<p>AAC, nebo pokro\u010dil\u00e9 k\u00f3dov\u00e1n\u00ed audia \u2014 v\u00fdpo\u010detn\u011b n\u00e1ro\u010dn\u00fd kodek, se z\u00e1va\u017en\u00fdm psychoakustick\u00fdm modelem. Z\u00edskal \u0161irok\u00e9 roz\u0161\u00ed\u0159en\u00ed pro audio na internetu, druh\u00fd nejpopul\u00e1rn\u011bj\u0161\u00ed po MP3. Vy\u017eaduje licencov\u00e1n\u00ed a licen\u010dn\u00ed poplatky: $15000 jednor\u00e1zov\u011b (nebo $1000 pro spole\u010dnosti s m\u00e9n\u011b ne\u017e 15 zam\u011bstnanci) + $0.98 za prvn\u00edch 500000 za\u0159\u00edzen\u00ed (<noindex><a rel=\"nofollow\" href=\"http:\/\/www.via-corp.com\/us\/en\/licensing\/aac\/licensefees.html\">zdroj<\/a><\/noindex>).<br \/>\nKodek je standardizov\u00e1n v r\u00e1mci specifikac\u00ed MPEG-2 a MPEG-4, a navzdory \u010dast\u00fdm omyl\u016fm, nepat\u0159\u00ed Apple.<\/p>\n<p>Vzorkovac\u00ed frekvence<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p>8 \u2014 96 kHz<br \/>\n8 \u2014 576 kbit\/s (pro stereo), 256 \u2014 320 kbit\/s (typick\u00e9 pro Bluetooth)<br \/>\nmacOS, Android 7+*, iOS<br \/>\n\u0160irok\u00fd v\u00fdb\u011br audio za\u0159\u00edzen\u00ed (hardwarov\u011b)<\/p>\n<p><i><b>*<\/b> pouze na za\u0159\u00edzen\u00edch, jejich\u017e v\u00fdrobci zaplatili licen\u010dn\u00ed poplatky<\/i><\/p>\n<p>V iOS a macOS se pou\u017e\u00edv\u00e1 nejlep\u0161\u00ed sou\u010dasn\u00fd k\u00f3dova\u010d Apple AAC, zaji\u0161\u0165uj\u00edc\u00ed maxim\u00e1ln\u011b mo\u017enou kvalitu audia. V Androidu se pou\u017e\u00edv\u00e1 druh\u00fd nejlep\u0161\u00ed k\u00f3dova\u010d Fraunhofer FDK AAC, ale mohou b\u00fdt pou\u017eity r\u016fzn\u00e9 hardwarov\u00e9, integrovan\u00e9 do platformy (SoC), s nezn\u00e1mou kvalitou k\u00f3dov\u00e1n\u00ed. <noindex><a rel=\"nofollow\" href=\"https:\/\/www.soundguys.com\/the-ultimate-guide-to-bluetooth-headphones-aac-20296\/\">Podle ned\u00e1vn\u00fdch test\u016f webu SoundGuys<\/a><\/noindex>, kvalita k\u00f3dov\u00e1n\u00ed AAC r\u016fzn\u00fdmi Android telefony se v\u00fdrazn\u011b li\u0161\u00ed:<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/www.soundguys.com\/wp-content\/uploads\/2018\/10\/aac-enhanced-view-fr-1200x788.jpg\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/7ae72554564f215dc765272065f5c97c.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p>U v\u011bt\u0161iny bezdr\u00e1tov\u00fdch audio za\u0159\u00edzen\u00ed pro AAC je maxim\u00e1ln\u00ed bitov\u00e1 rychlost nastavena na 320 kbps, n\u011bkter\u00e9 podporuj\u00ed pouze 256 kbps. Ostatn\u00ed bitov\u00e9 rychlosti se vyskytuj\u00ed velmi z\u0159\u00eddka.<br \/>\nAAC poskytuje vynikaj\u00edc\u00ed kvalitu p\u0159i bitov\u00fdch rychlostech 320 a 256 kbps, ale je n\u00e1chyln\u00fd <noindex><a rel=\"nofollow\" href=\"https:\/\/en.wikipedia.org\/wiki\/Generation_loss\">k ztr\u00e1t\u00e1m sekven\u010dn\u00edho k\u00f3dov\u00e1n\u00ed ji\u017e komprimovan\u00e9ho obsahu<\/a><\/noindex>, av\u0161ak sly\u0161et n\u011bjak\u00e9 rozd\u00edly s origin\u00e1lem na iOS p\u0159i bitov\u00e9 rychlosti 256 kbps je obt\u00ed\u017en\u00e9 i p\u0159i n\u011bkolika sekven\u010dn\u00edch k\u00f3dov\u00e1n\u00edch, p\u0159i jedin\u00e9m k\u00f3dov\u00e1n\u00ed, nap\u0159\u00edklad MP3 320 kbps do AAC 256 kbps, jsou ztr\u00e1ty zanedbateln\u00e9.<br \/>\nStejn\u011b jako u ostatn\u00edch Bluetooth kodek\u016f, jak\u00e1koli hudba je nejprve dek\u00f3dov\u00e1na a pot\u00e9 k\u00f3dov\u00e1na kodekem. P\u0159i p\u0159ehr\u00e1v\u00e1n\u00ed hudby ve form\u00e1tu AAC je nejprve dek\u00f3dov\u00e1na opera\u010dn\u00edm syst\u00e9mem a pot\u00e9 je znovu k\u00f3dov\u00e1na do AAC pro p\u0159enos p\u0159es Bluetooth. To je nezbytn\u00e9 pro m\u00edch\u00e1n\u00ed n\u011bkolika audio stream\u016f, nap\u0159\u00edklad hudby a ozn\u00e1men\u00ed o nov\u00e9 zpr\u00e1v\u011b. iOS nen\u00ed v\u00fdjimkou. Na internetu je mnoho tvrzen\u00ed, \u017ee na iOS se hudba ve form\u00e1tu AAC nep\u0159ek\u00f3duje p\u0159i p\u0159enosu p\u0159es Bluetooth, co\u017e je nespr\u00e1vn\u00e9.<\/p>\n<p><\/p>\n<h2>MP1\/2\/3<\/h2>\n<p>Kodeky rodiny MPEG-1\/2 Part 3 zahrnuj\u00ed zn\u00e1m\u00fd a \u0161iroce pou\u017e\u00edvan\u00fd MP3, m\u00e9n\u011b roz\u0161\u00ed\u0159en\u00fd MP2 (pou\u017e\u00edv\u00e1 se p\u0159ev\u00e1\u017en\u011b v digit\u00e1ln\u00ed TV a r\u00e1diu) a zcela nezn\u00e1m\u00fd MP1.<\/p>\n<p>Star\u00e9 kodeky MP1 a MP2 nejsou v\u016fbec podporov\u00e1ny: nena\u0161el jsem \u017e\u00e1dn\u00e1 sluch\u00e1tka ani \u017e\u00e1dn\u00fd Bluetooth stack, kter\u00fd by je k\u00f3doval nebo dek\u00f3doval.<br \/>\nDek\u00f3dov\u00e1n\u00ed MP3 je podporov\u00e1no n\u011bkter\u00fdmi sluch\u00e1tky, ale k\u00f3dov\u00e1n\u00ed nen\u00ed podporov\u00e1no v \u017e\u00e1dn\u00e9m stacku modern\u00edch opera\u010dn\u00edch syst\u00e9m\u016f. Zd\u00e1 se, \u017ee t\u0159et\u00ed strana BlueSoleil pro Windows m\u016f\u017ee k\u00f3dovat do MP3, pokud ru\u010dn\u011b uprav\u00edte konfigura\u010dn\u00ed soubor, ale jeho instalace mi zp\u016fsobuje BSoD na Windows 10. V\u00fdsledkem je, \u017ee kodek se vlastn\u011b ned\u00e1 pou\u017e\u00edvat pro Bluetooth audio.<br \/>\nD\u0159\u00edve, v letech 2006-2008, p\u0159ed roz\u0161\u00ed\u0159en\u00edm standardu A2DP v za\u0159\u00edzen\u00edch, lid\u00e9 poslouchali MP3 hudbu na sluch\u00e1tk\u00e1ch Nokia BH-501 prost\u0159ednictv\u00edm programu MSI BluePlayer, kter\u00fd byl dostupn\u00fd na Symbian a Windows Mobile. V t\u00e9 dob\u011b architektura opera\u010dn\u00edho syst\u00e9mu smartphon\u016f umo\u017e\u0148ovala p\u0159\u00edstup k mnoha n\u00edzko\u00farov\u0148ov\u00fdm funkc\u00edm a na Windows Mobile bylo dokonce mo\u017en\u00e9 instalovat t\u0159et\u00ed strany Bluetooth stacky.<\/p>\n<p>Posledn\u00ed patent kodeku MP3 vypr\u0161el, pou\u017e\u00edv\u00e1n\u00ed kodeku nevy\u017eaduje licen\u010dn\u00ed poplatky od 23. dubna 2017.<\/p>\n<blockquote><p>Pokud je nejd\u00e9le platn\u00fd patent uveden\u00fd v p\u0159edchoz\u00edch odkazech pova\u017eov\u00e1n za m\u011b\u0159\u00edtko, pak technologie MP3 se stala bezpatentovou v USA 16. dubna 2017, kdy\u017e vypr\u0161el americk\u00fd patent 6,009,399, kter\u00fd dr\u017eel a spravoval Technicolor.<\/p><\/blockquote>\n<p><i>Zdroj: <noindex><a rel=\"nofollow\" href=\"https:\/\/www.iis.fraunhofer.de\/en\/ff\/amm\/prod\/audiocodec\/audiocodecs\/mp3.html\">www.iis.fraunhofer.de\/en\/ff\/amm\/prod\/audiocodec\/audiocodecs\/mp3.html<\/a><\/noindex><\/i><\/p>\n<p>Vzorkovac\u00ed frekvence<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p>16 \u2014 48 kHz<br \/>\n8 \u2014 320 kbit\/s<br \/>\nNen\u00ed nikde podporov\u00e1no<br \/>\nN\u011bkter\u00fdmi audio za\u0159\u00edzen\u00edmi (hardwarov\u011b)<\/p>\n<h2>LDAC<\/h2>\n<p>Nov\u00fd a aktivn\u011b propagovan\u00fd \u201eHi-Res\u201c kodek od Sony, kter\u00fd podporuje vzorkovac\u00ed frekvence a\u017e 96 kHz a 24bitovou hloubku, s bitratem a\u017e 990 kbit\/s. Je inzerov\u00e1n jako audiofilsk\u00fd kodek, jako n\u00e1hrada za st\u00e1vaj\u00edc\u00ed Bluetooth kodeky. M\u00e1 funkci adaptivn\u00edho p\u0159izp\u016fsoben\u00ed bitrate v z\u00e1vislosti na podm\u00ednk\u00e1ch r\u00e1diov\u00e9ho vys\u00edl\u00e1n\u00ed.<\/p>\n<p>K\u00f3dova\u010d LDAC (<noindex><a rel=\"nofollow\" href=\"https:\/\/android.googlesource.com\/platform\/external\/libldac\/\">libldac<\/a><\/noindex>) je sou\u010d\u00e1st\u00ed standardn\u00ed v\u00fdbavy Androidu, tak\u017ee k\u00f3dov\u00e1n\u00ed je podporov\u00e1no na jak\u00e9mkoli smartphonu s Androidem, po\u010d\u00ednaje verz\u00ed 8. Softwarov\u00e9 dekod\u00e9ry nejsou ve\u0159ejn\u011b k dispozici, specifikace kodeku nen\u00ed \u0161irok\u00e9 ve\u0159ejnosti p\u0159\u00edstupn\u00e1, av\u0161ak p\u0159i prvn\u00edm pohledu na k\u00f3dova\u010d se zd\u00e1, \u017ee vnit\u0159n\u00ed konstrukce kodeku je podobn\u00e1 <noindex><a rel=\"nofollow\" href=\"https:\/\/en.wikipedia.org\/wiki\/Adaptive_Transform_Acoustic_Coding#ATRAC9\">ATRAC9<\/a><\/noindex> \u2014 kodeku od Sony, kter\u00fd se pou\u017e\u00edv\u00e1 v PlayStation 4 a Vita: oba pracuj\u00ed ve frekven\u010dn\u00edm rozsahu, pou\u017e\u00edvaj\u00ed modifikovanou diskr\u00e9tn\u00ed kosinovou transformaci (MDCT) a kompresi pomoc\u00ed Huffmanova algoritmu.<\/p>\n<p>Podpora LDAC je prakticky dostupn\u00e1 pouze na sluch\u00e1tk\u00e1ch od Sony. Mo\u017enost dek\u00f3dov\u00e1n\u00ed LDAC se ob\u010das objevuje na sluch\u00e1tk\u00e1ch a DAC jin\u00fdch v\u00fdrobc\u016f, ale velmi vz\u00e1cn\u011b.<\/p>\n<p>Vzorkovac\u00ed frekvence<br \/>\nBitrate<br \/>\nPodpora k\u00f3dov\u00e1n\u00ed<br \/>\nPodpora dek\u00f3dov\u00e1n\u00ed<\/p>\n<p>44.1 \u2014 96 kHz<br \/>\n303\/606\/909 kbit\/s (pro 44.1 a 88.2 kHz), 330\/660\/990 kbit\/s (pro 48 a 96 kHz)<br \/>\nAndroid 8+<br \/>\nN\u011bkter\u00fdmi sluch\u00e1tky Sony a jednotliv\u00fdmi za\u0159\u00edzen\u00edmi od jin\u00fdch v\u00fdrobc\u016f (hardwarov\u011b)<\/p>\n<p>Marketing LDAC jako Hi-Res kodeku po\u0161kozuje jeho technickou str\u00e1nku: je absurdn\u00ed pl\u00fdtvat bitrate na p\u0159enos nesly\u0161iteln\u00fdch lidsk\u00fdm uchem frekvenc\u00ed a zv\u00fd\u0161enou hloubkou, kdy\u017e nespl\u0148uje po\u017eadavky na p\u0159enos CD kvality (44.1\/16) bezztr\u00e1tov\u011b. Na\u0161t\u011bst\u00ed kodek m\u00e1 dva re\u017eimy provozu: p\u0159enos CD audio a p\u0159enos Hi-Res audio. V prvn\u00edm p\u0159\u00edpad\u011b se vzduchem p\u0159en\u00e1\u0161\u00ed pouze 44.1 kHz\/16 bit.<\/p>\n<p>Proto\u017ee softwarov\u00fd dekod\u00e9r LDAC nen\u00ed ve\u0159ejn\u011b k dispozici, nen\u00ed mo\u017en\u00e9 testovat kodek bez dal\u0161\u00edch za\u0159\u00edzen\u00ed, kter\u00e1 dek\u00f3duj\u00ed LDAC. Podle testu LDAC na DAC s jeho podporou, kter\u00fd in\u017een\u00fd\u0159i str\u00e1nky SoundGuys.com p\u0159ipojili p\u0159es digit\u00e1ln\u00ed v\u00fdstup a nahr\u00e1li generovan\u00fd zvuk na testovac\u00edch sign\u00e1lech, LDAC 660 a 990 kbit\/s v re\u017eimu CD kvality zaji\u0161\u0165uje pom\u011br sign\u00e1l\/\u0161um pon\u011bkud lep\u0161\u00ed ne\u017e u aptX HD.<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/www.soundguys.com\/wp-content\/uploads\/2018\/10\/LDAC-990-CD-Noise-Floor.jpg\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/819853ab9d92e9631454082ade245628.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><br \/>\n<i>Zdroj: <noindex><a rel=\"nofollow\" href=\"https:\/\/www.soundguys.com\/ldac-ultimate-bluetooth-guide-20026\/\">www.soundguys.com\/ldac-ultimate-bluetooth-guide-20026<\/a><\/noindex><\/i><\/p>\n<p>LDAC tak\u00e9 podporuje dynamick\u00fd bitov\u00fd tok mimo stanoven\u00e9 profily \u2014 od 138 kbit\/s do 990 kbit\/s, av\u0161ak, jak mohu posoudit, na Androidu se pou\u017e\u00edvaj\u00ed pouze standardizovan\u00e9 profily 303\/606\/909 a 330\/660\/990 kbit\/s.<\/p>\n<h2>Dal\u0161\u00ed kodeky<\/h2>\n<p>Jin\u00e9 A2DP kodeky se p\u0159\u00edli\u0161 neroz\u0161\u00ed\u0159ily. Jejich podpora bu\u010f chyb\u00ed t\u00e9m\u011b\u0159 \u00fapln\u011b, nebo je p\u0159\u00edtomna pouze na n\u011bkter\u00fdch modelech sluch\u00e1tek a chytr\u00fdch telefon\u016f.<br \/>\nStandardizovan\u00fd v A2DP kodek ATRAC nebyl nikdy pou\u017eit jako Bluetooth kodek ani samotn\u00fdmi Sony, kodeky Samsung HD, Samsung Scalable a Samsung UHQ-BT maj\u00ed velmi omezenou podporu ze strany p\u0159en\u00e1\u0161ej\u00edc\u00edch a p\u0159ij\u00edmaj\u00edc\u00edch za\u0159\u00edzen\u00ed, a HWA LHDC je p\u0159\u00edli\u0161 nov\u00fd a podporov\u00e1n pouze t\u0159emi(?) za\u0159\u00edzen\u00edmi.<\/p>\n<p><\/p>\n<h1>Podpora kodek\u016f audio za\u0159\u00edzen\u00edmi<\/h1>\n<p>Ne v\u0161ichni v\u00fdrobci zve\u0159ej\u0148uj\u00ed p\u0159esn\u00e9 informace o kodec\u00edch, kter\u00e9 podporuj\u00ed r\u016fzn\u00e9 bezdr\u00e1tov\u00e9 sluch\u00e1tka, reproduktory, p\u0159ij\u00edma\u010de nebo vys\u00edla\u010de. N\u011bkdy m\u016f\u017ee nastat situace, kdy podpora ur\u010dit\u00e9ho kodeku existuje jen pro vys\u00edl\u00e1n\u00ed, ale ne pro p\u0159\u00edjem (co\u017e plat\u00ed pro kombinovan\u00e9 vys\u00edla\u010de-p\u0159ij\u00edma\u010de), p\u0159i\u010dem\u017e v\u00fdrobce uv\u00e1d\u00ed pouze \"podporu\" bez dal\u0161\u00edch pozn\u00e1mek (p\u0159edpokl\u00e1d\u00e1m, \u017ee za to m\u016f\u017ee odd\u011blen\u00e9 licencov\u00e1n\u00ed encoder\u016f a decoder\u016f n\u011bkter\u00fdch kodek\u016f). U nejlevn\u011bj\u0161\u00edch za\u0159\u00edzen\u00ed nemus\u00ed b\u00fdt ozn\u00e1men\u00e1 podpora aptX v\u016fbec prok\u00e1z\u00e1na.<\/p>\n<p>Bohu\u017eel, v rozhran\u00edch v\u011bt\u0161iny opera\u010dn\u00edch syst\u00e9m\u016f nen\u00ed nikde zobrazen kodek, kter\u00fd se pou\u017e\u00edv\u00e1. Tato informace je k dispozici pouze na Androidu od verze 8 a na macOS. Nicm\u00e9n\u011b i v t\u011bchto opera\u010dn\u00edch syst\u00e9mech se zobraz\u00ed pouze ty kodeky, kter\u00e9 podporuje jak telefon\/po\u010d\u00edta\u010d, tak sluch\u00e1tka.<\/p>\n<p>Jak tedy zjistit, jak\u00e9 kodeky za\u0159\u00edzen\u00ed podporuje? Zaznamenat a analyzovat dump provozu s parametry dohod A2DP!<br \/>\nTo lze prov\u00e9st v Linuxu, macOS a Androidu. V Linuxu lze pou\u017e\u00edt Wireshark nebo hcidump, v macOS Bluetooth Explorer, a v Androidu vestav\u011bnou funkci pro ukl\u00e1d\u00e1n\u00ed Bluetooth HCI dumpu, kter\u00e1 je k dispozici v n\u00e1stroj\u00edch pro v\u00fdvoj\u00e1\u0159e. Z\u00edsk\u00e1te dump ve form\u00e1tu btsnoop, kter\u00fd lze nahr\u00e1t do analyz\u00e1toru Wireshark.<br \/>\n<b>Vezm\u011bte pros\u00edm na v\u011bdom\u00ed<\/b>Spr\u00e1vn\u00fd dump lze z\u00edskat pouze p\u0159ipojen\u00edm telefonu \/ po\u010d\u00edta\u010de k sluch\u00e1tk\u016fm \/ reproduktor\u016fm (jak absurdn\u011b to m\u016f\u017ee zn\u00edt)! Sluch\u00e1tka se mohou samostatn\u011b p\u0159ipojit k telefonu, a v takov\u00e9m p\u0159\u00edpad\u011b budou po\u017eadovat seznam kodek\u016f od telefonu, nikoli naopak. Aby bylo mo\u017en\u00e9 bezpochyby zaznamenat spr\u00e1vn\u00fd dump, nejprve p\u0159eru\u0161te sp\u00e1rov\u00e1n\u00ed s za\u0159\u00edzen\u00edm a pot\u00e9, b\u011bhem nahr\u00e1v\u00e1n\u00ed dumpu, sp\u00e1rujte telefon se sluch\u00e1tky.<\/p>\n<p>Pou\u017eijte n\u00e1sleduj\u00edc\u00ed filtr zobrazen\u00ed, abyste odfiltrovali nerelevantn\u00ed provoz:<\/p>\n<pre><code class=\"plaintext\">btavdtp.signal_id<\/code><\/pre>\n<p>Jako v\u00fdsledek byste m\u011bli vid\u011bt n\u011bco podobn\u00e9ho:<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/fv\/ku\/xs\/fvkuxsqcdwtxznupploqmldv9qm.png\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/b598f3282b36d7761c5f4fa63802d57e.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p>Na ka\u017ed\u00e9m bod\u011b p\u0159\u00edkazu GetCapabilities m\u016f\u017eete kliknout a zobrazit podrobn\u00e9 specifikace kodeku.<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/7s\/9a\/xa\/7s9axaeztya_dr2irptfi68ejxs.png\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/e5037fe18ae95ed7f047f4b8b8fcb2c8.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p>Wireshark nezn\u00e1 v\u0161echny identifik\u00e1tory kodek\u016f, tak\u017ee n\u011bkter\u00e9 kodeky bude t\u0159eba de\u0161ifrovat ru\u010dn\u011b podle tabulky identifik\u00e1tor\u016f n\u00ed\u017ee:<\/p>\n<pre><code class=\"plaintext\">Povinn\u00e9:\n0x00 - SBC\n\nVoliteln\u00e9:\n0x01 - MPEG-1,2 (aka MP3)\n0x02 - MPEG-2,4 (aka AAC)\n0x04 - ATRAC\n\nSpecifick\u00e9 pro v\u00fdrobce:\n0xFF 0x004F 0x01   - aptX\n0xFF 0x00D7 0x24   - aptX HD\n0xFF 0x000A 0x02   - aptX Low Latency\n0xFF 0x00D7 0x02   - aptX Low Latency\n0xFF 0x000A 0x01   - FastStream\n0xFF 0x012D 0xAA   - LDAC\n0xFF 0x0075 0x0102 - Samsung HD\n0xFF 0x0075 0x0103 - Samsung Scalable Codec\n0xFF 0x053A 0x484C - Savitech LHDC\n\n0xFF 0x000A 0x0104 - Identifik\u00e1tor kodeku CSR True Wireless Stereo v3 pro AAC\n0xFF 0x000A 0x0105 - Identifik\u00e1tor kodeku CSR True Wireless Stereo v3 pro MP3\n0xFF 0x000A 0x0106 - Identifik\u00e1tor kodeku CSR True Wireless Stereo v3 pro aptX<\/code><\/pre>\n<p>Abych nemusel analyzovat dumps ru\u010dn\u011b, vytvo\u0159il jsem slu\u017ebu, kter\u00e1 v\u0161e analyzuje automaticky: <noindex><a rel=\"nofollow\" href=\"https:\/\/btcodecs.valdikss.org.ru\">btcodecs.valdikss.org.ru<\/a><\/noindex><\/p>\n<p><\/p>\n<h1>Srovn\u00e1n\u00ed kodek\u016f. Kter\u00fd kodek je lep\u0161\u00ed?<\/h1>\n<p>Ka\u017ed\u00fd kodek m\u00e1 sv\u00e9 v\u00fdhody a nev\u00fdhody.<br \/>\naptX a aptX HD pou\u017e\u00edvaj\u00ed striktn\u011b dan\u00e9 profily, kter\u00e9 nelze zm\u011bnit bez modifikace encoderu a decoderu. Ani v\u00fdrobce telefonu, ani v\u00fdrobce sluch\u00e1tek nemohou zm\u011bnit bitrate nebo k\u00f3dovac\u00ed koeficienty aptX. Vlastn\u00edk kodeku, Qualcomm, vyd\u00e1v\u00e1 referen\u010dn\u00ed encoder ve form\u011b knihovny. Tato fakta p\u0159edstavuj\u00ed silnou str\u00e1nku aptX \u2014 p\u0159edem v\u00edte, jakou kvalitu zvuku dostanete, bez jak\u00fdchkoliv \"ale\".<\/p>\n<p>SBC m\u00e1 naopak mnoho p\u0159izp\u016fsobiteln\u00fdch mo\u017enost\u00ed, dynamick\u00fd bitrate (encoder m\u016f\u017ee sn\u00ed\u017eit parametr bitpool, pokud je r\u00e1diov\u00fd vys\u00edlac\u00ed sign\u00e1l p\u0159et\u00ed\u017een) a nem\u00e1 pevn\u011b stanoven\u00e9 profily, pouze doporu\u010den\u00e9 \"st\u0159edn\u00ed kvalita\" a \"vysok\u00e1 kvalita\", kter\u00e9 byly p\u0159id\u00e1ny do specifikace A2DP v roce 2003. \"Vysok\u00e1 kvalita\" u\u017e dle sou\u010dasn\u00fdch m\u011b\u0159\u00edtek nen\u00ed tak vysok\u00e1 a v\u011bt\u0161ina Bluetooth stack\u016f neumo\u017e\u0148uje pou\u017e\u00edvat parametry lep\u0161\u00ed, ne\u017e v profilu \"vysok\u00e1 kvalita\", i kdy\u017e technick\u00e1 omezen\u00ed pro to neexistuj\u00ed.<br \/>\nBluetooth SIG nem\u00e1 referen\u010dn\u00ed encoder SBC ve form\u011b knihovny a v\u00fdrobci jej implementuj\u00ed sami.<br \/>\nTo jsou slab\u00e9 str\u00e1nky SBC - nikdy nen\u00ed p\u0159edem jasn\u00e9, jak\u00e9 kvality zvuku lze o\u010dek\u00e1vat od konkr\u00e9tn\u00edho za\u0159\u00edzen\u00ed. SBC m\u016f\u017ee produkovat jak n\u00edzkou, tak velmi vysokou kvalitu zvuku, ale to posledn\u00ed nen\u00ed dosa\u017eiteln\u00e9 bez odebr\u00e1n\u00ed nebo obch\u00e1zen\u00ed um\u011bl\u00fdch omezen\u00ed Bluetooth stack\u016f.<\/p>\n<p>Situace s AAC je nejednozna\u010dn\u00e1: na jedn\u00e9 stran\u011b by m\u011bl codec teoreticky poskytovat kvalitu, kter\u00e1 nen\u00ed k nerozezn\u00e1n\u00ed od origin\u00e1lu, ale prax\u00ed, soud\u011b podle test\u016f laborato\u0159e SoundGuys na r\u016fzn\u00fdch Android za\u0159\u00edzen\u00edch, to nen\u00ed potvrzeno. Pravd\u011bpodobn\u011b je vina na n\u00edzkokvalitn\u00edch hardwarov\u00fdch audioencoderech integrovan\u00fdch do r\u016fzn\u00fdch \u010dipset\u016f telefon\u016f. M\u00e1 smysl pou\u017e\u00edvat AAC pouze na za\u0159\u00edzen\u00edch Apple, zat\u00edmco na Androidu se omezit na aptX a LDAC.<\/p>\n<p>Za\u0159\u00edzen\u00ed podporuj\u00edc\u00ed alternativn\u00ed codeky jsou obvykle vy\u0161\u0161\u00ed kvality, prost\u011b proto, \u017ee nen\u00ed smyslupln\u00e9 platit licen\u010dn\u00ed poplatky za pou\u017eit\u00ed t\u011bchto codec\u016f pro zcela levn\u00e1 n\u00edzkokvalitn\u00ed za\u0159\u00edzen\u00ed. Na z\u00e1klad\u011b m\u00fdch test\u016f zn\u00ed SBC velmi dob\u0159e na kvalitn\u00ed technice.<\/p>\n<p>Vytvo\u0159il jsem webovou slu\u017ebu, kter\u00e1 k\u00f3duje audio do SBC, aptX a aptX HD v re\u00e1ln\u00e9m \u010dase p\u0159\u00edmo v prohl\u00ed\u017ee\u010di. S jej\u00ed\u017e pomoc\u00ed m\u016f\u017eete testovat tyto audio codeky bez skute\u010dn\u00e9ho p\u0159enosu audia p\u0159es Bluetooth, na jak\u00fdchkoliv dr\u00e1tov\u00fdch sluch\u00e1tk\u00e1ch, reproduktorech a va\u0161\u00ed obl\u00edben\u00e9 hudb\u011b, tak\u00e9 m\u016f\u017eete m\u011bnit parametry k\u00f3dov\u00e1n\u00ed p\u0159\u00edmo b\u011bhem p\u0159ehr\u00e1v\u00e1n\u00ed audia:<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/btcodecs.valdikss.org.ru\/sbc-encoder\/\">btcodecs.valdikss.org.ru\/sbc-encoder<\/a><\/noindex><br \/>\nSlu\u017eba vyu\u017e\u00edv\u00e1 knihovny kod\u00e9ru SBC z projektu BlueZ a libopenaptx z ffmpeg, kter\u00e9 jsou kompilov\u00e1ny do WebAssembly a JavaScriptu z C, pomoc\u00ed emscripten, pro prov\u00e1d\u011bn\u00ed v prohl\u00ed\u017ee\u010di. Kdo by mohl sn\u00edt o takov\u00e9 budoucnosti!<\/p>\n<p>Takto to vypad\u00e1:<br \/>\n<video controls style=\"top: 0; left: 0; width: 100%; height: 100%; position: absolute;\">V\u00e1\u0161 prohl\u00ed\u017ee\u010d nepodporuje HTML5 video.<source src=\"https:\/\/files.catbox.moe\/9e9q8f.mp4\" type=\"video\/mp4\"><\/source><\/video><br \/>\nV\u0161imn\u011bte si, jak se m\u011bn\u00ed \u00farove\u0148 hluku po 20 kHz u r\u016fzn\u00fdch kodek\u016f. V origin\u00e1ln\u00edm MP3 souboru chyb\u00ed frekvence nad 20 kHz.<\/p>\n<p>Zkuste p\u0159ep\u00ednat mezi kodeky a posoudit, zda sly\u0161\u00edte rozd\u00edl mezi origin\u00e1lem, SBC 53 Joint Stereo (standardn\u00ed a nejroz\u0161\u00ed\u0159en\u011bj\u0161\u00ed profil) a aptX\/aptX HD.<\/p>\n<p><\/p>\n<h2>Sly\u0161\u00edm rozd\u00edl mezi kodeky <i>v sluch\u00e1tk\u00e1ch<\/i>!<\/h2>\n<p>Lid\u00e9, kte\u0159\u00ed b\u011bhem testov\u00e1n\u00ed p\u0159es webovou slu\u017ebu nesly\u0161\u00ed rozd\u00edl mezi kodeky, tvrd\u00ed, \u017ee ho sly\u0161\u00ed p\u0159i poslechu hudby v bezdr\u00e1tov\u00fdch sluch\u00e1tk\u00e1ch. Bohu\u017eel, to nen\u00ed vtip a ne efekt placebo: rozd\u00edl je skute\u010dn\u011b sly\u0161iteln\u00fd, av\u0161ak nen\u00ed zp\u016fsoben rozd\u00edly <i>kodeky<\/i>.<\/p>\n<p>Drtiv\u00e1 v\u011bt\u0161ina Bluetooth audio chipset\u016f pou\u017e\u00edvan\u00fdch v p\u0159ij\u00edmac\u00edch bezdr\u00e1tov\u00fdch za\u0159\u00edzen\u00edch je vybavena digit\u00e1ln\u00edm sign\u00e1ln\u00edm procesorem (Digital signal processor, DSP), kter\u00fd implementuje ekvaliz\u00e9r, kompresor, stereo roz\u0161i\u0159ova\u010d a dal\u0161\u00ed funkce ur\u010den\u00e9 k vylep\u0161en\u00ed (nebo zm\u011bn\u011b) zvuku. V\u00fdrobci Bluetooth za\u0159\u00edzen\u00ed mohou nastavit DSP <i>pro ka\u017ed\u00fd kodek zvl\u00e1\u0161\u0165<\/i>, a p\u0159i p\u0159ep\u00edn\u00e1n\u00ed mezi kodeky se poslucha\u010di m\u016f\u017ee zd\u00e1t, \u017ee sly\u0161\u00ed rozd\u00edly mezi hlasy kodek\u016f, zat\u00edmco ve skute\u010dnosti sly\u0161\u00ed r\u016fzn\u00e9 nastaven\u00ed DSP.<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/0j\/75\/rv\/0j75rvrbutguojyxx9yu0s-uang.png\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/6a8f7ab3ef52753cd32f398c023cd601.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><br \/>\n<i>DSP audio zpracovatelsk\u00fd obvod Kalimba ve chipsech vyroben\u00fdch CSR\/Qualcomm<\/i><\/p>\n<p><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/5dd07986d55d2e7e65697ab7114a942b.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<i>Aktivace r\u016fzn\u00fdch funkc\u00ed DSP pro ka\u017ed\u00fd kodek a v\u00fdstup samostatn\u011b<\/i><\/p>\n<p>N\u011bkter\u00e1 pr\u00e9miov\u00e1 za\u0159\u00edzen\u00ed jsou vybavena softwarem, kter\u00fd umo\u017e\u0148uje nastaven\u00ed parametr\u016f DSP, ale v\u011bt\u0161ina levn\u011bj\u0161\u00edch sluch\u00e1tek tuto mo\u017enost nem\u00e1 a u\u017eivatel\u00e9 nemohou vypnout post-processing zvuku standardn\u00edmi prost\u0159edky.<\/p>\n<p><\/p>\n<h2>Funk\u010dn\u00ed vlastnosti za\u0159\u00edzen\u00ed<\/h2>\n<p>Sou\u010dasn\u00e1 verze standardu A2DP m\u00e1 <b>funkci \u201eabsolutn\u00ed regulace hlasitosti\u201c<\/b> \u2014 \u0159\u00edzen\u00ed hlasitosti za\u0159\u00edzen\u00ed pomoc\u00ed speci\u00e1ln\u00edch p\u0159\u00edkaz\u016f protokolu AVRCP, kter\u00e9 upravuj\u00ed zes\u00edlen\u00ed v\u00fdstupn\u00edho stupn\u011b, m\u00edsto programov\u00e9ho sn\u00ed\u017een\u00ed hlasitosti audio streamu. Pokud p\u0159i zm\u011bn\u011b hlasitosti na sluch\u00e1tk\u00e1ch se hlasitost nesynchronizuje s hlasitost\u00ed na telefonu, znamen\u00e1 to, \u017ee va\u0161e sluch\u00e1tka nebo telefon tuto funkci nepodporuj\u00ed. V takov\u00e9m p\u0159\u00edpad\u011b m\u00e1 smysl poslouchat hudbu v\u017edy s maxim\u00e1ln\u00ed hlasitost\u00ed na telefonu a regulovat skute\u010dnou hlasitost tla\u010d\u00edtky na sluch\u00e1tk\u00e1ch \u2014 v tomto p\u0159\u00edpad\u011b bude pom\u011br sign\u00e1l\/\u0161um lep\u0161\u00ed a kvalita zvuku. <i>m\u011blo b\u00fdt<\/i> v\u00fd\u0161e.<br \/>\nVe skute\u010dnosti se v\u0161ak ob\u010das vyskytuj\u00ed smutn\u00e9 situace. Na m\u00fdch sluch\u00e1tk\u00e1ch RealForce OverDrive D1 je pro SBC zapnut\u00fd siln\u00fd kompresor, a zv\u00fd\u0161en\u00ed hlasitosti vede k zv\u00fd\u0161en\u00ed \u00farovn\u011b tich\u00fdch zvuk\u016f, zat\u00edmco hlasitost hlasit\u00fdch zvuk\u016f se nem\u011bn\u00ed (doch\u00e1z\u00ed k kompresi sign\u00e1lu). Z toho d\u016fvodu mus\u00edm nastavit hlasitost na po\u010d\u00edta\u010di p\u0159ibli\u017en\u011b na polovinu, v takov\u00e9m p\u0159\u00edpad\u011b efekt komprese prakticky neexistuje.<br \/>\nPodle m\u00fdch pozorov\u00e1n\u00ed v\u0161echny sluch\u00e1tka s dodate\u010dn\u00fdmi kodeky podporuj\u00ed funkci absolutn\u00edho \u0159\u00edzen\u00ed hlasitosti, z\u0159ejm\u011b je to jeden z po\u017eadavk\u016f na certifikaci kodek\u016f.<\/p>\n<p>N\u011bkter\u00e1 sluch\u00e1tka podporuj\u00ed <b>p\u0159ipojen\u00ed dvou za\u0159\u00edzen\u00ed sou\u010dasn\u011b<\/b>. To umo\u017e\u0148uje nap\u0159\u00edklad poslouchat hudbu z po\u010d\u00edta\u010de a p\u0159ij\u00edmat hovory z telefonu. Je v\u0161ak dobr\u00e9 v\u011bd\u011bt, \u017ee v tomto re\u017eimu jsou deaktivov\u00e1ny alternativn\u00ed kodeky a pou\u017e\u00edv\u00e1 se pouze SBC.<\/p>\n<p><b>Funkce AVDTP 1.3 Delay Reporting<\/b> umo\u017e\u0148uje sluch\u00e1tk\u016fm informovat p\u0159enosov\u00e9 za\u0159\u00edzen\u00ed o latenci, s jakou se zvuk skute\u010dn\u011b reprodukuje. To umo\u017e\u0148uje upravit synchronizaci audia s videem p\u0159i p\u0159ehr\u00e1v\u00e1n\u00ed video soubor\u016f: p\u0159i probl\u00e9mech s p\u0159enosem po r\u00e1diov\u00e9m vys\u00edl\u00e1n\u00ed, audio se nebude zpo\u017e\u010fovat za videem, naopak, video bude zpomaleno p\u0159ehr\u00e1va\u010dem videa, dokud se audio a video znovu nesynchronizuj\u00ed.<br \/>\nFunkce je podporov\u00e1na mnoha sluch\u00e1tky, Android 9+ a Linuxem s PulseAudio 12.0+. O podpo\u0159e funkce na jin\u00fdch platform\u00e1ch nem\u00e1m informace.<\/p>\n<p><\/p>\n<h1>Dvousm\u011brn\u00e1 komunikace p\u0159es Bluetooth. P\u0159enos hlasu.<\/h1>\n<p>Pro p\u0159enos hlasu p\u0159es Bluetooth se pou\u017e\u00edv\u00e1 Synchronous Connection Oriented (SCO) \u2014 synchronn\u00ed p\u0159enos s p\u0159edchoz\u00edm ujedn\u00e1n\u00edm spojen\u00ed. Tato metoda umo\u017e\u0148uje p\u0159en\u00e1\u0161et zvuk a hlas p\u0159esn\u011b v po\u0159ad\u00ed, se symetrickou rychlost\u00ed odes\u00edl\u00e1n\u00ed a p\u0159\u00edjmu, bez \u010dek\u00e1n\u00ed na potvrzen\u00ed p\u0159enosu a op\u011btovn\u00e9 odes\u00edl\u00e1n\u00ed paket\u016f. To sni\u017euje celkovou latenci p\u0159i p\u0159enosu zvuku p\u0159es r\u00e1diov\u00fd kan\u00e1l, ale klade v\u00e1\u017en\u00e1 omezen\u00ed na mno\u017estv\u00ed p\u0159en\u00e1\u0161en\u00fdch dat za jednotku \u010dasu a negativn\u011b ovliv\u0148uje kvalitu.<br \/>\nKdy\u017e se pou\u017e\u00edv\u00e1 tento re\u017eim, hlas i audio se p\u0159en\u00e1\u0161ej\u00ed se stejnou kvalitou.<br \/>\nBohu\u017eel, k roku 2019 je kvalita p\u0159enosu \u0159e\u010di p\u0159es Bluetooth st\u00e1le n\u00edzk\u00e1 a nen\u00ed jasn\u00e9, pro\u010d s t\u00edm Bluetooth SIG nic ned\u011bl\u00e1.<\/p>\n<h5>CVSD<\/h5>\n<p>Z\u00e1kladn\u00ed codec pro p\u0159enos \u0159e\u010di CVSD byl standardizov\u00e1n v roce 2002 a je podporov\u00e1n v\u0161emi za\u0159\u00edzen\u00edmi s obousm\u011brnou komunikac\u00ed p\u0159es Bluetooth. Zaji\u0161\u0165uje p\u0159enos audia s vzorkovac\u00ed frekvenc\u00ed 8 kHz, co\u017e odpov\u00edd\u00e1 kvalit\u011b b\u011b\u017en\u00e9 pevn\u00e9 telefonie. <\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/files.catbox.moe\/c4h77s.flac\">P\u0159\u00edklad z\u00e1znamu v tomto codec.<\/a><\/noindex>.<\/p>\n<h5>mSBC<\/h5>\n<p>Dal\u0161\u00ed codec mSBC byl standardizov\u00e1n v roce 2009 a v roce 2010 se ji\u017e objevily \u010dipy, kter\u00e9 jej pou\u017e\u00edvaj\u00ed pro p\u0159enos hlasu. mSBC je \u0161iroce podporov\u00e1n r\u016fzn\u00fdmi za\u0159\u00edzen\u00edmi.<br \/>\nNen\u00ed to nez\u00e1visl\u00fd codec, ale b\u011b\u017en\u00fd SBC ze standardu A2DP, s fixn\u00edm profilem k\u00f3dov\u00e1n\u00ed: 16 kHz, mono, bitpool 26.<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/files.catbox.moe\/b09joy.flac\">P\u0159\u00edklad z\u00e1znamu v tomto codec.<\/a><\/noindex>.<\/p>\n<p>Nen\u00ed to dokonal\u00e9, ale mnohem lep\u0161\u00ed ne\u017e CVSD, nicm\u00e9n\u011b je st\u00e1le nep\u0159\u00edjemn\u00e9 jej pou\u017e\u00edvat pro komunikaci p\u0159es internet, zejm\u00e9na kdy\u017e pou\u017e\u00edv\u00e1te sluch\u00e1tka pro komunikaci ve h\u0159e \u2014 zvuk hry bude tak\u00e9 p\u0159en\u00e1\u0161en s vzorkovac\u00ed frekvenc\u00ed 16 kHz.<\/p>\n<p>FastStreamSpole\u010dnost CSR se rozhodla rozvinout my\u0161lenku op\u011btovn\u00e9ho pou\u017eit\u00ed SBC. Aby se obe\u0161li omezen\u00ed protokolu SCO a vyu\u017eili vy\u0161\u0161\u00edch bitrate, CSR se vydala jinou cestou \u2014 zavedla podporu obousm\u011brn\u00e9ho SBC audia do standardu p\u0159enosu jednosm\u011brn\u00e9ho audia A2DP, standardizovala k\u00f3dovac\u00ed profily a nazvala to \u201eFastStream\u201c.<\/p>\n<p>FastStream p\u0159en\u00e1\u0161\u00ed do reproduktor\u016f stereozvuk 44,1 nebo 48 kHz s bitrate 212 kbit\/s, a pro p\u0159enos audia z mikrofonu se pou\u017e\u00edv\u00e1 mono, 16 kHz, s bitrate 72 kbit\/s (o n\u011bco lep\u0161\u00ed ne\u017e u mSBC). Takov\u00e9 parametry jsou mnohem lep\u0161\u00ed pro komunikaci v online hr\u00e1ch \u2014 zvuk hry a rozhovor\u016f bude kvalitn\u00ed.<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/files.catbox.moe\/4gazzt.flac\">P\u0159\u00edklad z\u00e1znamu v tomto codec.<\/a><\/noindex> (+ <noindex><a rel=\"nofollow\" href=\"https:\/\/files.catbox.moe\/b09joy.flac\">zvuk z mikrofonu, stejn\u00fd jako u mSBC<\/a><\/noindex>).<\/p>\n<p>Spole\u010dnost p\u0159i\u0161la s zaj\u00edmav\u00fdm \u0159e\u0161en\u00edm, ale proto\u017ee je v rozporu se standardem A2DP, jeho podpora existuje pouze v n\u011bkter\u00fdch vys\u00edla\u010d\u00edch t\u00e9to firmy (kter\u00e9 funguj\u00ed jako USB zvukov\u00e1 karta, nikoli jako Bluetooth za\u0159\u00edzen\u00ed), ale v Bluetooth streamech podporu nez\u00edskal, i kdy\u017e po\u010det sluch\u00e1tek s podporou FastStream nen\u00ed zanedbateln\u00fd.<\/p>\n<p>V sou\u010dasn\u00e9 dob\u011b je podpora FastStream v OS dostupn\u00e1 pouze <noindex><a rel=\"nofollow\" href=\"https:\/\/lists.freedesktop.org\/archives\/pulseaudio-discuss\/2019-June\/031175.html\">ve form\u00e1tu patche pro Linuxov\u00fd PulseAudio<\/a><\/noindex> od v\u00fdvoj\u00e1\u0159e Pali Roh\u00e1ra, kter\u00fd nen\u00ed zahrnut ve hlavn\u00ed v\u011btvi programu.<\/p>\n<h5>aptX Low Latency<\/h5>\n<p>K m\u00e9mu velk\u00e9mu p\u0159ekvapen\u00ed, aptX Low Latency tak\u00e9 podporuje obousm\u011brn\u00fd zvuk, implementuje stejn\u00fd princip jako FastStream.<br \/>\nTuto funkci kodeku nebude mo\u017en\u00e9 nikde vyu\u017e\u00edt \u2014 podpora dekomprese Low Latency nen\u00ed v \u017e\u00e1dn\u00e9m OS ani v \u017e\u00e1dn\u00e9m mn\u011b zn\u00e1m\u00e9m Bluetooth stacku.<\/p>\n<p><\/p>\n<h1>Bluetooth 5, Classic a Low Energy<\/h1>\n<p>Kolem specifikac\u00ed a verz\u00ed Bluetooth vzniklo velk\u00e9 zmaten\u00ed kv\u016fli existenci dvou nekompatibiln\u00edch standard\u016f pod jednou zna\u010dkou, oba z nich\u017e jsou \u0161iroce pou\u017e\u00edv\u00e1ny pro r\u016fzn\u00e9 \u00fa\u010dely.<\/p>\n<p>Existuj\u00ed dva r\u016fzn\u00e9, mezi sebou nekompatibiln\u00ed protokoly Bluetooth: Bluetooth Classic a Bluetooth Low Energy (LE, zn\u00e1m\u00fd tak\u00e9 jako Bluetooth Smart). Existuje tak\u00e9 t\u0159et\u00ed protokol, Bluetooth High Speed, ale ten nen\u00ed roz\u0161\u00ed\u0159en a nepou\u017e\u00edv\u00e1 se v spot\u0159ebitelsk\u00fdch za\u0159\u00edzen\u00edch.<\/p>\n<p>Od Bluetooth 4.0 se zm\u011bny ve specifikaci p\u0159ev\u00e1\u017en\u011b t\u00fdkaly Bluetooth Low Energy, zat\u00edmco verze Classic dostala pouze drobn\u00e1 vylep\u0161en\u00ed.<\/p>\n<p>Seznam zm\u011bn mezi Bluetooth 4.2 a Bluetooth 5:<\/p>\n<blockquote><p>9 ZM\u011aN OD v4.2 K 5.0<\/p>\n<p>9.1 NOV\u00c9 FUNKCE<\/p>\n<p>V Bluetooth Core Specification 5.0 jsou zavedeny n\u011bkter\u00e9 nov\u00e9 funkce. Hlavn\u00ed oblasti zlep\u0161en\u00ed jsou:<br \/>\n\u2022 Slot Availability Mask (SAM)<br \/>\n\u2022 2 Msym\/s PHY pro LE<br \/>\n\u2022 LE Long Range<br \/>\n\u2022 Vysok\u00e1 cyklick\u00e1 non-connectable reklama<br \/>\n\u2022 LE reklamn\u00ed roz\u0161\u00ed\u0159en\u00ed<br \/>\n\u2022 LE v\u00fdb\u011brov\u00fd algoritmus kan\u00e1l\u016f #2<br \/>\n9.1.1 Funkce p\u0159idan\u00e9 v CSA5 \u2014 integrov\u00e1ny ve v5.0<br \/>\n\u2022 Vy\u0161\u0161\u00ed v\u00fdstupn\u00ed v\u00fdkon<\/p><\/blockquote>\n<p><i>Zdroj: <noindex><a rel=\"nofollow\" href=\"https:\/\/www.bluetooth.org\/docman\/handlers\/DownloadDoc.ashx?doc_id=421043\">www.bluetooth.org\/docman\/handlers\/DownloadDoc.ashx?doc_id=421043<\/a><\/noindex> (strana 291)<\/i><\/p>\n<p>Pouze jedna zm\u011bna se dotkla verze Classic v r\u00e1mci specifikace Bluetooth 5: byla p\u0159id\u00e1na podpora technologie Slot Availability Mask (SAM), kter\u00e1 m\u00e1 zlep\u0161it rozd\u011blen\u00ed r\u00e1diov\u00e9ho spektra. V\u0161echny ostatn\u00ed zm\u011bny se t\u00fdkaj\u00ed pouze Bluetooth LE (a tak\u00e9 vy\u0161\u0161\u00edho v\u00fdstupn\u00edho v\u00fdkonu).<\/p>\n<p><b>V\u0161e<\/b> audio za\u0159\u00edzen\u00ed vyu\u017e\u00edvaj\u00ed pouze Bluetooth Classic. Sluch\u00e1tka a reproduktory nelze p\u0159ipojit p\u0159es Bluetooth Low Energy: neexistuje standard pro p\u0159enos audia pomoc\u00ed LE. Standard A2DP, pou\u017e\u00edvan\u00fd pro p\u0159enos vysoce kvalitn\u00edho audia, pracuje pouze p\u0159es Bluetooth Classic a jeho ekvivalent v LE neexistuje.<\/p>\n<p>Nen\u00ed smyslupln\u00e9 kupovat audio za\u0159\u00edzen\u00ed s Bluetooth 5 pouze kv\u016fli nov\u00e9 verzi protokolu. Bluetooth 4.0\/4.1\/4.2 bude v kontextu p\u0159enosu zvuku fungovat p\u0159esn\u011b stejn\u011b.<br \/>\nPokud ozn\u00e1men\u00ed nov\u00fdch sluch\u00e1tek zmi\u0148uje zdvojen\u00fd pracovn\u00ed r\u00e1dius a sn\u00ed\u017eenou spot\u0159ebu energie d\u00edky Bluetooth 5, v\u011bzte, \u017ee bu\u010f nerozum\u00ed tomu, co \u0159\u00edkaj\u00ed, nebo v\u00e1s uv\u00e1d\u011bj\u00ed v omyl. Nen\u00ed divu, \u017ee i v\u00fdrobci Bluetooth \u010dip\u016f se ve sv\u00fdch ozn\u00e1men\u00edch m\u00fdl\u00ed v rozd\u00edlech nov\u00e9 verze standardu, a n\u011bkter\u00e9 \u010dipy Bluetooth 5 podporuj\u00ed p\u00e1tou verzi pouze pro LE, zat\u00edmco pro Classic pou\u017e\u00edvaj\u00ed 4.2.<\/p>\n<h1>Zpo\u017ed\u011bn\u00ed p\u0159enosu zvuku<\/h1>\n<p>Hodnota zpo\u017ed\u011bn\u00ed zvuku z\u00e1vis\u00ed na mnoha faktorech: velikosti bufferu v audio stohu, v Bluetooth stohu a v samotn\u00e9m p\u0159ehr\u00e1vac\u00edm bezdr\u00e1tov\u00e9m za\u0159\u00edzen\u00ed, algoritmick\u00e9m zpo\u017ed\u011bn\u00ed kodeku.<\/p>\n<p>Zpo\u017ed\u011bn\u00ed jednoduch\u00fdch kodek\u016f, jako jsou SBC, aptX a aptX HD, je velmi mal\u00e9 a \u010din\u00ed 3-6 ms, co\u017e lze ignorovat, ale slo\u017eit\u00e9 kodeky, jako AAC a LDAC, mohou zp\u016fsobit znateln\u00e9 zpo\u017ed\u011bn\u00ed. Algoritmick\u00e9 zpo\u017ed\u011bn\u00ed AAC pro 44.1 kHz \u010din\u00ed 60 ms. LDAC \u2014 p\u0159ibli\u017en\u011b 30 ms (podle hrub\u00e9 anal\u00fdzy zdrojov\u00e9ho k\u00f3du. M\u00fdlit se mohu, ale ne moc.)<\/p>\n<p>Kone\u010dn\u00e9 zpo\u017ed\u011bn\u00ed siln\u011b z\u00e1vis\u00ed na p\u0159ehr\u00e1vac\u00edm za\u0159\u00edzen\u00ed, jeho \u010dipsetu a bufferu. B\u011bhem testov\u00e1n\u00ed jsem dostal rozptyl od 150 do 250 ms na r\u016fzn\u00fdch za\u0159\u00edzen\u00edch (s kodekem SBC). Pokud p\u0159edpokl\u00e1d\u00e1me, \u017ee za\u0159\u00edzen\u00ed, kter\u00e1 podporuj\u00ed dal\u0161\u00ed kodeky aptX, AAC a LDAC, pou\u017e\u00edvaj\u00ed kvalitn\u00ed komponenty a malou velikost bufferu, m\u00e1me n\u00e1sleduj\u00edc\u00ed typick\u00e1 zpo\u017ed\u011bn\u00ed:<\/p>\n<p>SBC: 150-250 ms<br \/>\naptX: 130-180 ms<br \/>\nAAC: 190-240 ms<br \/>\nLDAC: 160-210 ms<\/p>\n<p>P\u0159ipom\u00edn\u00e1m: aptX Low Latency nen\u00ed podporov\u00e1no v opera\u010dn\u00edch syst\u00e9mech, tak\u017ee men\u0161\u00ed zpo\u017ed\u011bn\u00ed lze z\u00edskat pouze spojen\u00edm transmitter+receiver nebo transmitter+sluch\u00e1tka\/reproduktor, p\u0159i\u010dem\u017e v\u0161echna za\u0159\u00edzen\u00ed mus\u00ed tento kodek podporovat.<\/p>\n<p><\/p>\n<h1>Probl\u00e9my s za\u0159\u00edzen\u00edmi, certifikac\u00ed a logy Bluetooth<\/h1>\n<p>Jak odli\u0161it kvalitn\u00ed audio za\u0159\u00edzen\u00ed od levn\u00e9 napodobeniny? Podle vzhledu, p\u0159edev\u0161\u00edm!<\/p>\n<p>Levn\u00e9 \u010d\u00ednsk\u00e9 sluch\u00e1tka, reproduktory a p\u0159ij\u00edma\u010de:<\/p>\n<ol>\n<li>Na krabici a za\u0159\u00edzen\u00ed chyb\u00ed slovo \u201eBluetooth\u201c, \u010dasto se pou\u017e\u00edv\u00e1 \u201eWireless\u201c a \u201eBT\u201c<\/li>\n<li>Chyb\u00ed logo Bluetooth <img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/bde65e4674a5d573c0482e64ea6ff2d3.png\" style=\"display:block;margin: 0 auto;\" \/> na krabici nebo za\u0159\u00edzen\u00ed<\/li>\n<li>Nen\u00ed modr\u00e1 blikaj\u00edc\u00ed LED dioda<\/li>\n<\/ol>\n<p>\nAbsence of these elements indicates that the device has not undergone certification, which means it is potentially low-quality and problematic. For instance, Bluedio headphones are not Bluetooth certified and do not fully comply with the A2DP specification. They would not pass certification.<\/p>\n<p>Let's consider several devices and their boxes:<br \/>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/e4\/qa\/rr\/e4qarrce8fcjv8wwu46aiyib3oa.jpeg\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/12b3b234a522eaef783b480e8f003ffc.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/ba\/06\/vb\/ba06vbcolhpvuie2xlbgnvsycd0.jpeg\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/da56314dd65a1000cd3b545d9925d08b.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/habrastorage.org\/webt\/mw\/1b\/t1\/mw1bt1hp0cz11xuilzyz0a70dca.jpeg\"><img decoding=\"async\" alt=\"Audio p\u0159es Bluetooth: maxim\u00e1ln\u00ed podrobnosti o profilech, kodec\u00edch a za\u0159\u00edzen\u00edch\" src=\"\/wp-content\/uploads\/2bb0356a92d8aee2a84c3123aa8d7e09.png\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p>All of these are uncertified devices. The manual may have a logo and the name of the Bluetooth technology, but the most important thing is that they appear on the box and\/or the device itself.<\/p>\n<p>If your headphones or speaker say \"Ze bluetooth dewise is connecteda successfulle,\" that also does not guarantee their quality:<br \/>\n<center><div class=\"youtube-placeholder\" data-id=\"TOFbsbGpIWk\" onclick=\"loadVideo(this)\">\r\n        <img decoding=\"async\" src=\"https:\/\/img.youtube.com\/vi\/TOFbsbGpIWk\/hqdefault.jpg\" alt=\"P\u0159ehr\u00e1t video\" loading=\"lazy\" width=\"480\" height=\"360\" style=\"width:100%;height:auto;\">\r\n        <div class=\"play-button\"><\/div>\r\n    <\/div><\/center><\/p>\n<p><\/p>\n<h1>Z\u00e1v\u011br<\/h1>\n<p>Can Bluetooth completely replace wired headphones and headsets? It can, but at the cost of reduced quality during calls, increased audio latency, which can be irritating in games, and a multitude of proprietary codecs that require licensing fees, raising the final cost of both smartphones and headphones.<\/p>\n<p>The marketing of alternative codecs is very strong: aptX and LDAC are presented as a much-anticipated replacement for the \"outdated and poor\" SBC, which is not as bad as commonly believed.<\/p>\n<p>As it turned out, artificial restrictions of Bluetooth stacks on the bitrate of SBC can be bypassed, so that SBC does not lag behind aptX HD. I took the initiative and created a patch for the LineageOS firmware: <noindex><a rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/post\/455316\/\">Modifikujeme Bluetooth stack pro zlep\u0161en\u00ed zvuku na sluch\u00e1tk\u00e1ch bez kodek\u016f AAC, aptX a LDAC<\/a><\/noindex><\/p>\n<p>More information can be found on the websites <noindex><a rel=\"nofollow\" href=\"https:\/\/www.soundguys.com\/\">SoundGuys<\/a><\/noindex> a <noindex><a rel=\"nofollow\" href=\"http:\/\/soundexpert.org\/\">SoundExpert<\/a><\/noindex>.<\/p>\n<p><b>Bonus:<\/b> <noindex><a rel=\"nofollow\" href=\"https:\/\/files.catbox.moe\/29l4kd.zip\">reference SBC encoder, information about the A2DP bitstream and test files<\/a><\/noindex>. This file was previously available on the Bluetooth website, but is now only accessible to those who joined Bluetooth SIG.<\/p>\n<p>Zdroj: <a content=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/post\/427997\/\">habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u0418\u0437-\u0437\u0430 \u043c\u0430\u0441\u0441\u043e\u0432\u043e\u0433\u043e \u0432\u044b\u043f\u0443\u0441\u043a\u0430 \u0441\u043c\u0430\u0440\u0442\u0444\u043e\u043d\u043e\u0432 \u0431\u0435\u0437 \u0430\u0443\u0434\u0438\u043e\u0440\u0430\u0437\u044a\u0435\u043c\u0430 3.5 \u043c\u043c \u0431\u0435\u0441\u043f\u0440\u043e\u0432\u043e\u0434\u043d\u044b\u0435 Bluetooth-\u043d\u0430\u0443\u0448\u043d\u0438\u043a\u0438 \u0434\u043b\u044f \u043c\u043d\u043e\u0433\u0438\u0445 \u0441\u0442\u0430\u043b\u0438 \u043e\u0441\u043d\u043e\u0432\u043d\u044b\u043c \u0441\u043f\u043e\u0441\u043e\u0431\u043e\u043c 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[&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-35145","post","type-post","status-publish","format-standard","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.3 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u0418\u0437-\u0437\u0430 \u043c\u0430\u0441\u0441\u043e\u0432\u043e\u0433\u043e.\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<meta name=\"author\" content=\"Yuri Gagarin\"\/>\n\t<link rel=\"canonical\" href=\"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/audio-cherez-bluetooth-maksimalno-podrobno-o-profilyah-kodekah-i-ustrojstvah\" \/>\n\t\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 5.0.3\" \/>\n\t\t<meta 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