Fotokozani zomwe mawu sangathe kufotokoza; kumva zosiyanasiyana zomverera zopiringizika mu mphepo yamkuntho kumverera; kuswa dziko lapansi, thambo ngakhalenso thambo lenilenilo, kupita ulendo wopanda mapu, misewu, palibe zizindikiro; yambitsani, fotokozerani ndikukumana ndi nkhani yonse yomwe ikhalabe yapadera komanso yosayerekezeka. Zonsezi zikhoza kuchitika ndi nyimbo - luso lomwe lakhalapo kwa zaka zikwi zambiri ndipo limakondweretsa makutu ndi mitima yathu.
Komabe, nyimbo, kapena ntchito zoimbira, sizingangogwiritsa ntchito zokometsera zokha, komanso kufalitsa zidziwitso zomwe zili mkati mwake, zomwe zimapangidwira chipangizo china komanso chosawoneka kwa omvera. Lero tidziwana ndi kafukufuku wachilendo kwambiri momwe ophunzira omaliza maphunziro a ETH Zurich adatha, osadziwika ndi khutu la munthu, kudziwitsa zina mwazoimba nyimbo, chifukwa chake nyimboyo imakhala njira yotumizira deta. Kodi kwenikweni adagwiritsa ntchito bwanji ukadaulo wawo, kodi nyimbo zomwe zili ndi komanso zopanda deta yophatikizidwa ndizosiyana kwambiri, ndipo mayeso othandiza adawonetsa chiyani? Timaphunzira za izi kuchokera ku lipoti la ofufuza. Pitani.
Maziko ofufuza
Ofufuzawo amatcha ukadaulo wawo waukadaulo wamakina acoustic data transmission. Wokamba nkhani akamayimba nyimbo yosinthidwa, munthu amawona kuti ndi yachilendo, koma, mwachitsanzo, foni yamakono imatha kuwerenga chidziwitso cha encoded pakati pa mizere, kapena pakati pa zolembazo, titero kunena kwake. Asayansi (chowona chakuti anyamatawa akadali ophunzira omaliza maphunziro sikuwalepheretsa kukhala asayansi) kuyitanitsa liwiro ndi kudalirika kwa kufalitsa pamene kusunga mlingo wa magawowa, mosasamala kanthu za fayilo yosankhidwa yosankhidwa, monga gawo lofunika kwambiri pakukhazikitsa njira yotengera deta iyi. Psychoacoustics, yomwe imaphunzira zamaganizidwe ndi machitidwe amunthu pamawu, imathandizira kuthana ndi ntchitoyi.
Pachimake pakufalitsa kwa data yamayimbidwe amatha kutchedwa OFDM (orthogonal frequency division multiplexing), yomwe, limodzi ndi kusintha kwa ma subcarriers kumayendedwe anyimbo pakapita nthawi, zidapangitsa kuti zitheke kugwiritsa ntchito kwambiri ma frequency opatsirana pakufalitsa zidziwitso. Chifukwa cha izi, zinali zotheka kukwaniritsa liwiro la 412 bps pamtunda wa mamita 24 (zolakwika <10%). Kuyesera kothandiza kophatikizapo odzipereka 40 kunatsimikizira chenicheni chakuti nkosatheka kumva kusiyana pakati pa nyimbo yoyambirira ndi imene chidziΕ΅itsocho chinaikidwamo.
Kodi luso limeneli lingagwiritsidwe ntchito pati? Ochita kafukufuku ali ndi yankho lawo: pafupifupi mafoni onse amakono, ma laputopu ndi zida zina zam'manja zili ndi maikolofoni, ndipo malo ambiri apagulu (macafe, malo odyera, malo ogulitsira, ndi zina zambiri) amakhala ndi okamba nyimbo zakumbuyo. Nyimbo yakumbuyo iyi, mwachitsanzo, ingaphatikizepo data yolumikizira netiweki ya Wi-Fi popanda kufunikira kowonjezera.
Zomwe zimakhudzidwa ndi kufalitsa kwa data yamayimbidwe zamveka bwino kwa ife; tsopano tiyeni tipitirire ku kafukufuku watsatanetsatane wa dongosolo lino.
Kufotokozera Kwadongosolo
Kuyika kwa data munyimbo kumachitika chifukwa cha kubisa pafupipafupi. Pakapita nthawi, ma frequency a masking amadziwika ndipo zonyamula za OFDM zomwe zili pafupi ndi izi zimadzaza ndi data.
Chithunzi #1: Kutembenuza fayilo yoyambirira kukhala siginecha yophatikizika (nyimbo + data) yofalitsidwa kudzera mwa okamba.
Poyamba, chizindikiro choyambirira cha audio chimagawidwa m'magawo otsatizana kuti awunikenso. Chigawo chilichonse chotere (Hi) cha L = 8820 zitsanzo, chofanana ndi 200 ms, chikuchulukitsidwa ndi zenera* kuchepetsa zotsatira za malire.
Zenera* ndi ntchito yolemetsa yomwe imagwiritsidwa ntchito kuwongolera zotsatira chifukwa cha sidelobes pakuyerekeza kwa spectral.
Kenako, ma frequency akulu a siginecha yoyambirira adapezeka kuchokera pa 500 Hz mpaka 9.8 kHz, zomwe zidapangitsa kuti pakhale ma frequency a masking fM,l pagawoli. Kuphatikiza apo, deta idatumizidwa pang'onopang'ono kuchokera ku 9.8 mpaka 10 kHz kuti ikhazikitse malo a subcarriers pa wolandila. Malire apamwamba a ma frequency omwe amagwiritsidwa ntchito adayikidwa ku 10 kHz chifukwa chakuchepa kwa ma maikolofoni a smartphone pama frequency apamwamba.
Ma frequency a masking adatsimikiziridwa pagawo lililonse lowunikidwa payekhapayekha. Pogwiritsa ntchito njira ya HPS (Harmonic Product Spectrum), ma frequency atatu otsogola adadziwika ndikuzungulira mpaka zolemba zapafupi pa sikelo ya harmonic chromatic. Umu ndi momwe zolemba zazikulu fF, i = 1β¦3 zinapezedwa, zomwe zili pakati pa makiyi C0 (16.35 Hz) ndi B0 (30.87 Hz). Kutengera mfundo yoti manotsi ofunikira ndi otsika kwambiri kuti agwiritsidwe ntchito potumiza deta, ma octave awo apamwamba 500kfF, i adawerengedwa mumitundu ya 9.8 Hz ... 2 kHz. Ambiri mwa ma frequency awa (fO,l1) adadziwika kwambiri chifukwa cha mawonekedwe a HPS.
Chithunzi #2: Ma octave owerengetsera a FO,l1 pamalingaliro ofunikira ndi maulalo fH,l2 a kamvekedwe kolimba kwambiri.
Zotsatira za ma octave ndi ma harmonics zidagwiritsidwa ntchito ngati ma frequency a masking, pomwe ma OFDM subcarrier fSC,k adachokera. Ma subcarriers awiri adayikidwa pansipa komanso pamwamba pa ma frequency amtundu uliwonse.
Kenako, mawonekedwe a gawo la nyimbo la Hi adasefedwera pa subcarrier fSC, k. Pambuyo pake, chizindikiro cha OFDM chidapangidwa kutengera zidziwitso za Bi, chifukwa chomwe gawo lophatikizika la Ci litha kufalitsidwa kudzera mwa wokamba nkhani. Kukula ndi magawo a subcarriers ayenera kusankhidwa kuti wolandirayo athe kuchotsa deta yofalitsidwa pamene womvera sakuwona kusintha kwa nyimbo.
Chithunzi Nambala 3: gawo la sipekitiramu ndi mafupipafupi amtundu wa Hi gawo la nyimbo yoyambirira.
Pamene siginecha yomvera yomwe ili ndi zidziwitso zolembedwamo ikuseweredwa kudzera mwa okamba, maikolofoni ya chipangizo cholandila imajambula. Kuti mupeze malo oyambira azizindikiro za OFDM, zolembedwazo ziyenera kusefedwa kaye. Mwa njira iyi, maulendo apamwamba amachotsedwa, pomwe palibe zizindikiro zosokoneza nyimbo pakati pa subcarriers. Mutha kupeza zoyambira zazizindikiro za OFDM pogwiritsa ntchito cyclic prefix.
Pambuyo pozindikira kuyambika kwa zizindikilo za OFDM, wolandila amapeza zidziwitso zamanotsi otsogola kwambiri kudzera pakuwongolera pafupipafupi kwa domain. Kuphatikiza apo, OFDM imalimbana kwambiri ndi magwero osokoneza a narrowband, chifukwa amangokhudza ma subcarriers ena.
Mayesero othandiza
Wokamba nkhani wa KRK Rokit 8 adakhala ngati gwero la nyimbo zosinthidwa, ndipo foni yamakono ya Nexus 5X idasewera gawo la phwando lolandira.
Chithunzi #4: Kusiyana pakati pa OFDM yeniyeni ndi nsonga zamalumikizidwe zoyezedwa m'nyumba pa 5m pakati pa sipika ndi maikolofoni.
Mfundo zambiri za OFDM zili pakati pa 0 mpaka 25 ms, kotero mutha kupeza zoyambira zovomerezeka mkati mwa 66.6 ms cyclic prefix. Ofufuzawo akuwona kuti wolandila (pakuyesa uku, foni yam'manja) amaganizira kuti zizindikilo za OFDM zimaseweredwa nthawi ndi nthawi, zomwe zimapangitsa kuzindikira kwawo.
Chinthu choyamba kuyang'ana chinali zotsatira za mtunda pa bit error rate (BER). Kuti achite zimenezi, mayesero atatu anachitidwa mβzipinda zamitundu yosiyanasiyana: khonde lokhala ndi kapeti, ofesi yokhala ndi linoleum pansi, ndi holo yokhala ndi matabwa pansi.
Nyimbo "And The Cradle Will Rock" yolemba Van Halen idasankhidwa kukhala phunziro loyesedwa.
Voliyumu ya mawu idasinthidwa kotero kuti kuchuluka kwa mawu kuyeza ndi foni yamakono pamtunda wa 2 m kuchokera kwa wokamba nkhani kunali 63 dB.
Chithunzi Nambala 5: Zizindikiro za BER malingana ndi mtunda pakati pa wokamba nkhani ndi maikolofoni (mzere wabuluu - omvera, wobiriwira - korido, lalanje - ofesi).
Mumsewu, phokoso la 40 dB linatengedwa ndi foni yamakono pamtunda wa mamita 24 kuchokera kwa wokamba nkhani. M'kalasi pamtunda wa 15 mamita phokoso linali 55 dB, ndipo mu ofesi pamtunda wa mamita 8 mlingo wa phokoso lodziwika ndi foni yamakono unafika 57 dB.
Chifukwa holo ndi ofesi zimakhala zowoneka bwino, zizindikiro zochedwa za OFDM zimapitilira kutalika kwa prefix ndikuwonjezera BER.
Reverberation* - kutsika kwapang'onopang'ono kwamphamvu ya mawu chifukwa cha mawonekedwe ake angapo.
Ofufuzawa adawonetsanso kusinthasintha kwa machitidwe awo poyigwiritsa ntchito ku nyimbo za 6 kuchokera kumitundu itatu (tebulo pansipa).
Gulu 1: nyimbo zomwe zimagwiritsidwa ntchito poyesa.
Komanso, kupyolera mu deta ya tebulo, tikhoza kuona mlingo wochepa ndi mitengo yolakwika ya nyimbo iliyonse. Mitengo ya deta ndi yosiyana chifukwa kusiyana kwa BPSK (phase shift keying) kumagwira ntchito bwino pamene ma subcarriers omwewo amagwiritsidwa ntchito. Ndipo izi ndizotheka pamene zigawo zoyandikana zili ndi zinthu zofanana zophimba. Nyimbo zaphokoso mosalekeza zimapereka maziko oyenera obisala chifukwa ma frequency obisala amakhala amphamvu kwambiri pama frequency osiyanasiyana. Nyimbo zothamanga zimatha kubisa zizindikiro za OFDM pang'ono chifukwa chautali wokhazikika wazenera lowunikira.
Kenako, anthu anayamba kuyesa dongosolo, amene ankafunika kudziwa kuti ndi nyimbo yotani yomwe inali yoyambirira komanso yomwe inasinthidwa ndi chidziwitso chomwe chili mmenemo. Pachifukwa ichi, zolemba za 12-masekondi a nyimbo kuchokera pa tebulo No. 1 zinayikidwa pa webusaiti yapadera.
Pakuyesa koyamba (E1), wophunzira aliyense adapatsidwa chidutswa chosinthidwa kapena choyambirira kuti amvetsere ndipo adayenera kusankha ngati chidutswacho chinali choyambirira kapena chosinthidwa. Pakuyesa kwachiwiri (E2), otenga nawo mbali amatha kumvera matembenuzidwe onsewo kangapo momwe amafunira, kenako ndikusankha yomwe inali yoyambirira komanso yomwe idasinthidwa.
Gulu 2: zotsatira za zoyeserera E1 ndi E2.
Zotsatira zakuyesa koyamba zili ndi zizindikiro ziwiri: p(O|O) - kuchuluka kwa omwe adayika nyimbo yoyambirira ndi p(O|M) - kuchuluka kwa omwe adalemba nyimbo yomwe idasinthidwa kukhala yoyambirira.
Chochititsa chidwi n'chakuti, ochita kafukufuku ena, malinga ndi ofufuzawo, adawona nyimbo zina zosinthidwa kukhala zoyambirira kuposa zoyambirira zomwezo. Avereji ya zoyeserera zonse ziwiri ikuwonetsa kuti womvera wamba sangazindikire kusiyana pakati pa nyimbo yanthawi zonse ndi yomwe data idayikidwamo.
Mwachibadwa, akatswiri a nyimbo ndi oimba adzatha kuzindikira zolakwika zina ndi zinthu zokayikitsa mβnyimbo zosinthidwa, koma zinthu zimenezi sizofunika kwambiri moti zingabweretse mavuto.
Ndipo tsopano ife tokha tikhoza kutenga nawo mbali mu kuyesera. M'munsimu muli mitundu iwiri ya nyimbo imodzi - yoyamba ndi yosinthidwa. Kodi mukumva kusiyana kwake?
vs
Kuti mudziwe zambiri za ma nuances a phunziroli, ndikupangira kuyang'ana gulu lofufuza.
Mutha kutsitsanso zolemba zakale za ZIP zamafayilo amawu a nyimbo zoyambira ndi zosinthidwa zomwe zidagwiritsidwa ntchito mu phunziroli .
Epilogue
Mu ntchitoyi, ophunzira omaliza maphunziro a ETH Zurich adalongosola njira yodabwitsa yotumizira ma data mkati mwa nyimbo. Kuti achite izi, adagwiritsa ntchito masking pafupipafupi, zomwe zidapangitsa kuti zitheke kuyika deta munyimbo yomwe wokamba nkhaniyo amaimba. Nyimboyi imazindikiridwa ndi maikolofoni ya chipangizocho, chomwe chimazindikira deta yobisika ndikuyisintha, pamene omvera ambiri sangazindikire kusiyana kwake. M'tsogolomu, anyamatawo akukonzekera kupanga dongosolo lawo, ndikusankha njira zowonjezera zowonjezera deta mu audio.
Pamene wina abwera ndi chinthu chachilendo, ndipo chofunika kwambiri, chinachake chimene chimagwira ntchito, timakhala osangalala nthawi zonse. Koma chosangalatsa kwambiri nβchakuti zimenezi zinapangidwa ndi achinyamata. Sayansi ilibe zoletsa zaka. Ndipo ngati achinyamata apeza sayansi yotopetsa, ndiye kuti ikufotokozedwa molakwika, titero kunena kwake. Kupatula apo, monga tikudziwira, sayansi ndi dziko lodabwitsa lomwe silimatha kudabwitsa.
Lachisanu Lachisanu:
Popeza tikukamba za nyimbo, kapena nyimbo za rock, apa pali ulendo wodabwitsa wodutsa mumtunda wa rock.
Mfumukazi, "Radio Ga Ga" (1984).
Zikomo powerenga, khalani ndi chidwi, komanso khalani ndi sabata yabwino anyamata! π
Zikomo chifukwa chokhala nafe. Kodi mumakonda zolemba zathu? Mukufuna kuwona zambiri zosangalatsa? Tithandizeni potipatsa oda kapena kulimbikitsa anzathu, 30% kuchotsera kwa ogwiritsa ntchito a Habr pa analogi yapadera yamaseva olowera, omwe tinapangira inu: (ikupezeka ndi RAID1 ndi RAID10, mpaka 24 cores mpaka 40GB DDR4).
Dell R730xd 2 nthawi zotsika mtengo? Pokhapokha ku Netherlands! Dell R420 - 2x E5-2430 2.2Ghz 6C 128GB DDR3 2x960GB SSD 1Gbps 100TB - kuchokera $99! Werengani za
Source: www.habr.com