Waa maxay AAC-format?

Si aad u taariikhda, AAC-format weli ma gaarin qaybinta mass of sidayaal dhawaaqa, si kastaba ha ahaatee, tiro ka mid ah oo xuduudaheedu waa ka xoogbadan, dhammaan noocyada kala duwan ee hadda jira ee riixo audio, oo sidaas daraaddeed mid istaahila in aannu ogaanno.

Waa maxay?

Waxaan ka bilaabeynaa qeexid: format audio AAC waa lahaansho file maqal ah (xiranayo) mid ka mid ah riixo. Isla mar ahaantaana waxa uu leeyahay khasaare yar oo tayo leh inta lagu jiro sireed badan MP3 at xaaladaha heerka xoogaa isku. Sidoo kale, AAC-format waa isku geynta koodh ah wideband audio in uu isticmaalaa labo mabda 'ugu weyn habaynteeda inay si weyn u yareeyo tirada xogta looga baahan yahay gudbinta of audio digital oo tayo sare leh. xal Tan waxaa loo arkaa in ay mid ka mid ah ugu tayada sareeya, iibiyaa khasaare of technology riixo. format wuxuu taageeraa qalabka ugu casrisan, xataa qaadi karo. Waa in la ogaadaa in codadka tilifoonka qaab AAC ah waxaa laga gadan karaa Store iTunes ah, iyo in kaydkan yihiin music, Tifaftirayaasha keliya by yahay go'aanka. Waa in sidoo kale lagu sheegay in AAC-format asal ahaan abuuray bedelka a in MP3, kaas oo ku siin kara koodh tayada hagaagay. Go'aanka waxaa la daabacay 1997 sida cusub, 7-dii, qayb ka mid ah qoyska reer MPEG-2.

Mabda 'hawlgalka

Marka habaynteeda qaab this, habka soo socda: Qaybaha shucaaca dismo signalka la saaraa, nadiifiyaa of eryis signal audio ka encoded. Intaas ka dib, xogta la farsameeyo iyadoo la raacayo habka sida ay MDCT ay kakanaanta. At marxaladda soo socota codes waxaa lagu daray si loo saxo khaladaadka gudaha kala duwan. Ugu dambeyntii, signal la isku qaadsiiyo ama ku badbaadi.

All faahfaahinta

Waxa xiiso leh, ka AAC-format ayaa inta jeer sampling ee u dhexeeya 8-96 Khz iyo tirada channels in bareeg ah 1-48 ah. MP3 Hybrid isticmaalaa set oo ah filtarrada. Waxaa loola jeedaa a cosine Discrete modified beddesho, in AAC jeedo heerka kordhaysa oo ah "daaqadaha", kaas oo uu gaaro 2048 dhibcood.

Sayidka, AAC ka badan ayaa ku haboon in encode webigu ku audio isagoo garaaca wadnaha iyo square-ruxruxo calaamadaha adag, iyadoo MP3 marka la barbar dhigo. Format helay awood u leh inay dynamically beddelato ee dhererka block MDCT kala duwan 2048-256 dhibcood. Haddii ay jirto a waqti-gaaban ama hal wareeg ah, loo isticmaalo a "window" yar 256 dhibcood si loo gaaro xal wanaagsan. Xaaladdan oo kale, sida caadiga ah waa 2048-dhibic weyn "window" si loo kordhiyo tayada shaqo koodh ah. AAC uu leeyahay tiro ka mid ah faa'iidooyinka la MP3 caadiga ah marka la barbar dhigo. iyaga ka mid ah waa in aan ku xuso: xaqiijinta tiro badan oo ah channels audio (ilaa iyo 48), oolnimada weyn sireed ku hoos jira xaalad heerka qayb joogto ah iyo variable iyo inta jeer sampling kala duwan ka soo 8 Hz in 96 Khz, (waayo, MP3, tiradaasi waa laga 8 Hz 48 Khz) iyo hab-abbuurka khaas ah laguna magacaabo rikoodh Joint. Sida xal, "AAC +" - codec ah oo diiradda lagu saaray heerka xoogaa yar yahay shaqada. Waa isku darka of SBR iyo LC AAC, oon ku gaari karo dhawaaqa wanaagsan horeba kala duwan ee 32-48 kbit / s.