Chikamu chechipiri:
Chero raster image inogona kumiririrwa mufomu maviri-dimensional matrix. Kana zvasvika kune mavara, pfungwa inogona kuvandudzwa nekutarisa mufananidzo se matatu-dimensional matrix, umo mamwe zviyero zvinoshandiswa kuchengetedza data kune imwe neimwe yemavara.
Kana tikafunga ruvara rwekupedzisira sekubatanidzwa kwezvinonzi. mavara ekutanga (tsvuku, girini uye bhuruu), mumatriki edu matatu-dimensional tinotsanangura ndege nhatu: yekutanga yetsvuku, yechipiri yegirini uye yekupedzisira yebhuruu.
Tichadaidza poindi imwe neimwe mune ino matrix pixel (chifananidzo chechinhu). Pixel yega yega ine ruzivo nezve kusimba (kazhinji senhamba kukosha) yevara rega rega. Semuyenzaniso, dzvuku pixel zvinoreva kuti ine 0 yegirini, 0 yebhuruu uye yakanyanya tsvuku. Pink pixel inogona kuumbwa uchishandisa musanganiswa wemavara matatu. Uchishandisa nhamba kubva pa0 kusvika pa255, pikisi yepink inotsanangurwa se Tsvuku = 255, Girini = 192 ΠΈ Bhuruu = 203.
Ichi chinyorwa chakaburitswa nerutsigiro rweEDISON.Tiri kusimukira , uye zvakare takapfimbwa .
Dzimwe nzira dzekukodha mufananidzo weruvara
Kune mamwe akawanda mamodheru ekumiririra mavara anoumba mufananidzo. Semuenzaniso, unogona kushandisa indexed palette, iyo inoda chete byte imwe chete kuti imiririre pixel yega yega, pane matatu anodiwa kana uchishandisa RGB modhi. Mumuenzaniso wakadaro, zvinokwanisika kushandisa 2D matrix panzvimbo ye 3D matrix kumiririra ruvara rwega. Izvi zvinochengetedza ndangariro, asi zvinopa diki color gamut.
RGB
Somuenzaniso, tarisa mufananidzo uri pasi apa. Chiso chekutanga chakanyatsopendwa. Mamwe ndiwo ndege dzvuku, girini uye bhuruu (kusimba kwemavara anoenderana anoratidzwa mune greyscale).
Tinoona kuti mimvuri yakatsvuka mune yepakutanga ichave munzvimbo dzakafanana apo zvikamu zvinopenya zvechiso chechipiri zvinoonekwa. Kunyange zvazvo mupiro webhuruu unogona kunyanya kuonekwa mumaziso aMario (chiso chekupedzisira) uye zvinhu zvezvipfeko zvake. Ziva uko ndege dzese nhatu dzemavara dzinopa zvishoma (nzvimbo dzakasviba dzemifananidzo) - Masharubu aMario.
Kuti uchengetedze kusimba kwemavara ega ega, imwe nhamba yebhiti inodiwa - huwandu uhu hunodanwa kudzika zvishoma. Ngatitii mabhiti masere ashandiswa (zvichienderana neukoshi kubva pa8 kusvika pa0) parudzi rwendege. Zvadaro tine kudzika kwemavara e255 bits (24 bits * 8 R / G / B ndege).
Imwe pfuma yemufananidzo ndeye ΡΠ°Π·ΡΠ΅ΡΠ΅Π½ΠΈΠ΅, inova nhamba yepixels mune imwe dimension. Kazhinji inotsanangurwa se hupamhi Γ kureba, sezvakaita 4 by 4 muenzaniso mufananidzo pazasi.
Chimwe chivakwa chatinobata nacho kana tichishanda nemifananidzo / mavhidhiyo chimiro chakaringana, ichitsanangura hukama hwakajairika pakati pehupamhi nekukwirira kwemufananidzo kana pixel.
Pavanotaura kuti imwe firimu kana kuti mufananidzo wa16 ne9 muhukuru, vanowanzoreva kuratidza chikamu ratio (DAR - kubva Ratidza Aspect ratio) Nekudaro, dzimwe nguva panogona kunge paine akasiyana maumbirwo emapikisi ega - mune ino nyaya yatiri kutaura nezvayo pixel ratio (BY - kubva Pixel Aspect ratio).
Chiziviso kune muenzi: DVD ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ck DAR 4 kusvika 3
Kunyangwe iyo chaiyo DVD resolution iri 704x480, ichiri kuchengetedza 4: 3 chimiro chechiyero nekuti PAR iri 10:11 (704x10 / 480x11).
Uye pakupedzisira, tinogona kusarudza Π²ΠΈΠ΄Π΅ΠΎ sekutevedzana kwe n mafuremu enguva yacho nguva, iyo inogona kutorwa seimwe chiyero. A n zvino chiyero chefuremu kana nhamba yemafuremu pasekondi (the - kubva Mafreyimu paChipiri).
Huwandu hwemabhiti pasekondi inodiwa kuratidza vhidhiyo ndeyayo kukurumidza kutapurirana - bitrate.
bitrate = upamhi * kureba * bit kudzika * mafuremu pasekondi
Semuenzaniso, 30 fps, 24 bps, 480x240 vhidhiyo inoda 82,944,000 bps kana 82,944 Mbps (30x480x240x24) - asi kana pasina nzira yekumanikidza inoshandiswa.
Kana kuchinjisa kasi inenge isingachinji, yobva yanzi nguva dzose kutapurirana kumhanya (CBR - kubva nguva dzose bit rate) Asi zvinogonawo kusiyana, munyaya iyi inonzi variable baud rate (VBR - kubva kusiyanisa bit rate).
Iyi girafu inoratidza yakaganhurirwa VBR, uko kusina mabhiti akawandisa akaraswa mune yakasviba rakazara furemu.
Mainjiniya pakutanga vakagadzira nzira yekupeta kaviri yaifungidzirwa furemu chiyero chevhidhiyo kuratidzwa pasina kushandisa imwe bandwidth. Iyi nzira inozivikanwa se vhidhiyo yakabatanidzwa; Chaizvoizvo, inotumira hafu yechidzitiro mu "frame" yekutanga uye imwe hafu mu "frame" inotevera.
Parizvino, mapikicha anoshandiswa zvakanyanya inofambira mberi scanning matekinoroji. Inzira yekuratidza, kuchengeta kana kutumira mifananidzo inofamba umo mitsetse yese yefuremu yega yega inodhirowa zvakatevedzana.
Zvakanaka! Iye zvino tava kuziva kuti chifananidzo chinomiririrwa sei nedhijitari, marongerwo arwo mavara, mabhiti mangani pasekondi yatinoshandisa kuratidza vhidhiyo, kana chiyero chebhiti chiripo (CBR) kana chinoshanduka (VBR). Isu tinoziva nezvechisarudzo chakapihwa tichishandisa yakapihwa furemu chiyero, isu tinoziva mamwe akawanda mazwi, akadai seyakabatanidzwa vhidhiyo, PAR uye mamwe mamwe.
Kubvisa redundancy
Zvinozivikanwa kuti vhidhiyo isina compression haigone kushandiswa zvakajairika. Vhidhiyo yeawa yakareba pa720p resolution uye 30 mafuremu pasekondi yaizotora 278 GB. Tinosvika pakukosha uku nekuwanza 1280 x 720 x 24 x 30 x 3600 (hupamhi, kureba, bits per pixel, FPS uye nguva mumasekonzi).
Shandisa kusarasikirwa kwekumanikidza algorithms, kufanana neDEFLATE (inoshandiswa muPKZIP, Gzip uye PNG), haingaderedzi bandwidth inodiwa zvakakwana. Isu tinofanirwa kutsvaga dzimwe nzira dzekumanikidza vhidhiyo.
Kuti uite izvi, unogona kushandisa maitiro echiono chedu. Isu tiri nani pakusiyanisa kupenya pane ruvara. Vhidhiyo inoteedzana yemifananidzo inoteedzana inodzokorora nekufamba kwenguva. Pane misiyano midiki pakati pemafuremu ari pedyo echiitiko chimwechete. Pamusoro pezvo, furemu yega yega ine nzvimbo dzakawanda dzinoshandisa yakafanana (kana yakafanana) ruvara.
Ruvara, kupenya uye maziso edu
Maziso edu anonyanya kuona kupenya pane kuva neruvara. Iwe unogona kuzvionera iwe pachako nekutarisa mufananidzo uyu.
Kana iwe usingaoni kuti kuruboshwe hafu yemufananidzo mavara ezvikwere A ΠΈ B zvakafanana, saka ndizvo zvakajairika. Uropi hwedu hunotimanikidza kubhadhara zvakanyanya kuchiedza nemumvuri pane kuvara. Kurutivi rworudyi pakati pezvikwere zvakatarwa pane jumper yeruvara rumwechete - saka isu (kureva uropi hwedu) tinoona zviri nyore kuti, chokwadi, iwo akafanana ruvara.
Ngatitarisei (nenzira iri nyore) kuti maziso edu anoshanda sei. Ziso inhengo yakaoma kunzwisisa ine zvikamu zvakawanda. Nekudaro, isu tinonyanya kufarira makoni uye tsvimbo. Ziso rine miriyoni 120 tsvimbo uye 6 miriyoni makoni.
Ngatitarisei maonerwo eruvara uye kupenya semabasa akaparadzana ezvimwe zvikamu zveziso (chaizvoizvo, zvese zvakatonyanya kuoma, asi isu tichazvirerutsa). Masero etsvimbo ndiwo anonyanya kukonzeresa kupenya, ukuwo masero ekoni anokonzera ruvara. Makoni akakamurwa kuva marudzi matatu, zvichienderana nepigment yavainayo: S-cones (blue), M-cones (girinhi), uye L-cones (tsvuku).
Sezvo tine matanda akawanda (kupenya) kupfuura makoni (ruvara), tinogona kugumisa kuti isu tinokwanisa kusiyanisa shanduko pakati perima nechiedza pane mavara.
Kusiyana Sensitivity Features
Vatsvagiri mukuyedza psychology uye mamwe akawanda minda vakagadzira dzidziso dzakawanda dzekuona kwevanhu. Uye mumwe wavo anonzi kusiyana kwekunzwa mabasa. Izvo zvine hukama nekuvhenekera kwenzvimbo uye kwechinguvana. Muchidimbu, ndezvekuti ingani shanduko dzinodiwa mucherechedzi asati azviona. Cherechedza huzhinji hwezwi rokuti "basa". Izvi zvinokonzerwa nekuti isu tinokwanisa kuyera kusiyana kwekunzwa mabasa kwete chete kune nhema uye chena mifananidzo, asiwo yemavara. Migumisiro yezviedzo izvi inoratidza kuti kazhinji maziso edu anonyanya kuona kupenya pane kupenya.
Sezvo tichiziva kuti isu tinonzwa zvakanyanya kupenya kwemufananidzo, tinogona kuedza kushandisa chokwadi ichi.
Rudzi modhi
Isu takafunga zvishoma nzira yekushanda nemifananidzo yemavara tichishandisa iyo RGB chirongwa. Kune mamwe mamodheru zvakare. Pane modhi inoparadzanisa luminance kubva kuchroma uye inozivikanwa se YCbCr. Nenzira, kune mamwe mamodheru anoita kupatsanurwa kwakafanana, asi isu tichangofunga izvi chete.
Mumuenzaniso uyu wemavara Y inomiririra kupenya, uye zvakare inoshandisa nzira mbiri dzemavara: Cb (blue blue) uye Cr (yakapfuma mutsvuku). YCbCr inogona kutorwa kubva kuRGB, uye kutendeuka kutendeuka kunogoneka zvakare. Tichishandisa iyi modhi tinogona kugadzira yakazara mavara mifananidzo sezvatinoona pazasi:
Shandura pakati peYCbCr neRGB
Mumwe munhu achapikisa: zvinokwanisika sei kuwana mavara ose kana girini isingashandisi?
Kupindura mubvunzo uyu, ngatishandure RGB kuita YCbCr. Ngatishandisei coefficients yakagamuchirwa muyero BT. 601, iyo yakakurudzirwa nechikwata ITU-R. Ichi chikamu chinoisa zviyero zvevhidhiyo yedhijitari. Somuenzaniso: chii chinonzi 4K? Chii chinofanira kunge chiri chiyero chechimiro, kugadzirisa, modhi yemavara?
Kutanga ngativerengei kupenya. Ngatishandisei maconstants akakurudzirwa neITU uye totsiva iyo RGB tsika.
Y = 0.299R + 0.587G + 0.114B
Mushure mekunge tave nekupenya, tichaparadzanisa bhuruu neruvara rutsvuku:
Cb = 0.564(B - Y)
Cr = 0.713(R - Y)
Uye isu tinogona zvakare kushandura kumashure uye kunyange kuwana girini tichishandisa YCbCr:
R = Y + 1.402Cr
B = Y + 1.772Cb
G = Y - 0.344Cb - 0.714Cr
Kazhinji, zviratidzo (mamonitor, maTV, masikirini, nezvimwewo) shandisa chete RGB modhi. Asi iyi modhi inogona kurongeka nenzira dzakasiyana:
Colour subsampling
Nemufananidzo unomiririrwa semusanganiswa weruvheneko uye chrominance, tinogona kushandisa kunzwisiswa kukuru kwemaitiro emunhu kune kupenya pane chrominance nekubvisa ruzivo. Chroma subsampling inzira yekukodha mifananidzo uchishandisa kushomeka kwechroma pane kupenya.
Yakawanda sei inotenderwa kuderedza kugadzirisa kwemavara?! Zvinoitika kuti patova nemamwe madhayagiramu anotsanangura mabatiro ekugadzirisa nekubatanidza (Resulting Color = Y + Cb + Cr).
Zvirongwa izvi zvinozivikanwa se downsampling systems uye inoratidzwa sechikamu che3-fold - a:x:y, iyo inosarudza huwandu hwemasamples ekupenya uye mavara akasiyana masaini.
a - horizontal sampling standard (kazhinji yakaenzana ne4)
x - nhamba yemasampuli echroma mumutsara wekutanga wemapikseli (yakatwasuka resolution inoenderana ne a)
y - nhamba yeshanduko mumasampuli echroma pakati pemitsara yekutanga neyechipiri yepixels.
Kunze ndiko 4:1:0, ichipa imwe chroma sampuli mune yega yega 4-by-4 luminance resolution block.
Zvirongwa zvakajairika zvinoshandiswa mumacodecs emazuva ano:
- 4:4:4 (hapana downsampling)
- 4:2:2
- 4:1:1
- 4:2:0
- 4:1:0
- 3:1:1
YCbCr 4:2:0 - musanganiswa muenzaniso
Heino mufananidzo wakabatanidzwa uchishandisa YCbCr 4:2:0. Ziva kuti tiri kungoshandisa 12 bits per pixel.
Izvi ndizvo zvakaita mufananidzo mumwechete, wakavharwa nemhando huru dzemavara subsampling. Mutsara wekutanga ndiyo yekupedzisira YCbCr, mutsetse wepasi unoratidza chroma resolution. Migumisiro yakanaka kwazvo, tichifunga nezvekurasikirwa kuduku muhutano.
Rangarira patakaverenga 278 GB yenzvimbo yekuchengetedza kuchengetedza awa-yakareba vhidhiyo faira pa720p resolution uye 30 mafuremu pasekondi? Kana tikashandisa YCbCr 4:2:0, saka saizi iyi ichaderedzwa nehafu - 139 GB. Kusvika ikozvino, ichiri kure nemugumisiro unogamuchirwa.
Unogona kuwana iyo YCbCr histogram iwe pachako uchishandisa FFmpeg. Mumufananidzo uyu, bhuruu inotonga pamusoro petsvuku, iyo inonyatsooneka mu histogram pachayo.
Ruvara, kupenya, ruvara gamut - vhidhiyo wongororo
Tinokurudzira kuona iyi vhidhiyo inoshamisa. Inotsanangura kuti kupenya chii, uye kazhinji madotsi ese ane madoti Ρ pamusoro pekupenya uye ruvara.
Frame Types
Ngatienderere mberi. Ngatiedzei kubvisa nguva redundancy. Asi chekutanga, ngatitsanangure mamwe mazwi ekutanga. Ngatitii tine bhaisikopo rine 30 mafuremu pasekondi, heino mafaremu ayo mana ekutanga:
Tinogona kuona kudzokorora kwakawanda mumafuremu: semuenzaniso, yebhuruu kumashure isingashanduke kubva kune furemu kuenda kune furemu. Kugadzirisa dambudziko iri, tinogona kuaisa muzvikamu zvitatu zvemafuremu.
I-frame (Intro Frame)
I-frame (referensi furemu, kiyi furemu, yemukati furemu) inozvimiririra. Zvisinei kuti chii chaunoda kuona, I-frame inenge iri mufananidzo wakamira. Yekutanga furemu inowanzova I-frame, asi isu tinogara tichiona I-mafuremu kunyangwe pakati peasati ekutanga mafuremu.
P-frame (PRedicted Frame)
P-frame (predictive frame) inotora mukana wekuti nguva dzose mufananidzo wazvino unogona kudhindwa uchishandisa iyo yapfuura furemu. Semuenzaniso, muchikamu chechipiri shanduko chete ibhora rinoenda kumberi. Tinogona kuwana furemu 2 nekungogadzirisa zvishoma furemu 1, tichingoshandisa mutsauko pakati pemafuremu aya. Kugadzira furemu 2, isu tinoreva kune yakapfuura furemu 1.
β
B-frame (Bi-predictive Frame)
Zvakadini nezvinongedzo kwete kune zvakapfuura chete, asiwo kune ramangwana mafuremu kuti ape kunyange nani compression?! Iyi ndiyo B-frame (bidirectional furemu).
β β
Kubvisa kwepakati
Aya marudzi emafuremu anoshandiswa kupa yakanyanya kunaka kudzvanya. Tichatarisa kuti izvi zvinoitika sei muchikamu chinotevera. Parizvino, ngationei kuti "inodhura" zvakanyanya maererano nendangariro inopedzwa iI-furemu, iyo P-frame inooneka yakachipa, asi iyo inonyanya kubatsira sarudzo yevhidhiyo iB-frame.
Temporal redundancy (inter-frame prediction)
Ngatitarisei kuti ndedzipi sarudzo dzatinadzo kuti tideredze kudzokorora nekufamba kwenguva. Isu tinokwanisa kugadzirisa rudzi urwu rwedundancy tichishandisa nzira dzekufungidzira.
Isu tichaedza kushandisa mashoma mabhiti sezvinobvira encode kutevedzana kwemafuremu 0 uye 1.
Tinogona kugadzira kubvisa, tinongobvisa furemu 1 kubva pachigadziko 0. Isu tinowana furemu 1, tinongoshandisa mutsauko pakati payo neyakapfuura furemu, isu tinongovhara zvakasara zvakasara.
Asi ko kana ndikakuudza kuti pane imwe nzira iri nani iyo inoshandisa kunyange mashoma mabhiti?! Chekutanga, ngatipwanye furemu 0 kuita gidhi rakajeka rine mabhuroko. Uye zvino tichaedza kuenzanisa zvivharo kubva pamapuranga 0 nemapuranga 1. Mune mamwe mazwi, tichafungidzira kufamba pakati pemapuranga.
Kubva kuWikipedia - block motion muripo
Muripo weBlock motion unokamura chimiro chazvino kuita zvisinga pindire mabhuroko uye iyo motion compensation vector inoshuma kwakabva mablock (pfungwa isiriyo yakajairika ndeyekuti. zvakapfuura furemu yakakamurwa kuita mabhuroko asina kupindirana, uye mafambisirwo emuripo anozivisa kwainoenda zvivharo izvozvo. Asi muchokwadi, ndiyo imwe nzira yakatenderedza - haisi iyo yapfuura furemu inoongororwa, asi inotevera; hazvisi pachena kuti zvivharo zviri kufamba kupi, asi kwaakabva). Kazhinji sosi mabhuraki anopindirana mune sosi furemu. Mamwe mavhidhiyo compression algorithms anounganidza iyo yazvino furemu kubva kuzvikamu kwete kana imwe chete, asi akati wandei akambotapurirwa mafuremu.
Munguva yekuongorora, tinoona kuti bhora rabva kubva (x= 0, y=25) ne (x= 6, y=26), kukosha x ΠΈ y sarudza kufamba vector. Imwe nhanho yatinogona kuita kuchengetedza mabheti ndeyekukodha chete mutsauko wemafambiro ekufambisa pakati peyekupedzisira block chinzvimbo uye yakafanotaurwa, saka yekupedzisira kufambisa vector ichave (x=6-0=6, y=26-25=1 )
Mumamiriro ezvinhu chaiwo, bhora iri raizokamurwa kuita n blocks, asi izvi hazvishandure musimboti wenyaya.
Zvinhu zviri mufuremu zvinofamba mumativi matatu, saka kana bhora richifamba, rinogona kuita diki rinoonekwa (kana kukura kana richienda kumuoni). Zvakajairika kuti hapazove nemutambo wakakwana pakati pemabhuroko. Heano maonero akasanganiswa ekufungidzira kwedu uye mufananidzo chaiwo.
Asi isu tinoona kuti kana isu tichishandisa fungidziro yekufamba, pane zvinooneka zvishoma data rekodhi pane kana uchishandisa nzira iri nyore yekuverenga delta pakati pemafuremu.
Muripo chaiwo wekufamba ungaite sei
Iyi nzira inoshandiswa kune ese mabhuroko kamwechete. Kazhinji bhora redu rinofamba rine mamiriro richakamurwa kuita mabhuroko akati wandei kamwechete.
Iwe unogona kuwana kunzwa kune aya mazano iwe pachako uchishandisa .
Kuti uone mafambiro ekufambisa, unogona kugadzira vhidhiyo yekufungidzira yekunze uchishandisa .
Unogonawo kushandisa (inobhadharwa, asi kune muyedzo wemahara unogumira kumafuremu gumi ekutanga chete).
Spatial redundancy (yemukati fungidziro)
Kana tikaongorora furemu yega yega muvhidhiyo, tinowana nzvimbo dzakawanda dzakabatana.
Ngatitarisei muenzaniso uyu. Ichi chiitiko chinonyanya kuumbwa nebhuruu nechena mavara.
Iyi i-I-frame. Hatigone kutora mafuremu apfuura ekufanotaura, asi isu tinogona kuzvimanikidza. Ngatiisei encode kusarudzwa kweiyo red block. Kana tikatarisa vavakidzani vayo, tinoona kuti kune mamwe mavara emavara akaipoteredza.
Isu tinofungidzira kuti mavara akapararira akamira mufuremu. Zvinoreva kuti ruvara rwepikisi isingazivikanwe ichave nehunhu hwevavakidzani vayo.
Mafungiro akadaro anogona kuzova asina kururama. Ndicho chikonzero nei iwe unofanirwa kushandisa nzira iyi (yemukati fungidziro), uye wobva wabvisa iwo chaiwo maitiro. Izvi zvichatipa yakasara bhuroka, izvo zvinozoita kuti iwedzere kudzvanywa matrix kana ichienzaniswa neyekutanga.
Kana iwe uchida kudzidzira nekufungidzira kwemukati, unogona kugadzira vhidhiyo ye macroblocks uye kufanotaura kwavo uchishandisa ffmpeg. Kuti unzwisise zvinorehwa neruvara rwega rwega, uchafanirwa kuverenga ffmpeg zvinyorwa.
Kana iwe unogona kushandisa Intel Vhidhiyo Pro Analyzer (sezvandambotaura pamusoro, iyo yemahara vhezheni inogumira kune gumi ekutanga mafuremu, asi izvi zvichakukwanira iwe pakutanga).
Chikamu chechipiri:
Source: www.habr.com