Ib lub codec yog ib qho kev siv algorithm (OK ua tau yooj yim - txoj kev ntawm ib qhov kev pab cuam!), Feem ntau ntawm cov sij hawm ntsia ua ib qho software rau ib tug neeg rau zaub mov lossis muaj nyob hauv ib qho cuab yeej kho ( ATA , IP Phone etc.), uas yog siv los hloov lub suab (hauv VoIP) qhov teeb meem tawm hauv cov ntaub ntawv xov tooj kom xa mus rau hauv Internet los sis txhua lub network thaum hu VoIP.
Lo lus codec los ntawm cov lo lus coder-decoder los yog compressor-decompressor. Codecs nquag tau ua raws li peb yam hauv qab no (tsawg tsawg ua qhov kawg):
- Encoding - seev suab
- Ntaus - tawm suab
- Encryption - Decryption
Encoding - seev suab
Thaum koj tham dhau lub xov tooj PSTN, koj lub suab yog thauj mus rau hauv ib txoj kab analog hauv xov tooj. Tiam sis nrog VoIP, koj lub suab yog hloov mus rau hauv cov teeb meem digital. Qhov kev hloov no yog technically hu ua encoding, thiab yog tau los ntawm lub codec. Thaum lub suab digitized mus txog nws cov lo lus uas peb, nws yuav tsum tau rov qab hais dua rov qab mus rau nws tus thawj analog lub xeev kom lwm tus neeg sau xov xwm tau hnov thiab to taub nws.
Ntaus - tawm suab
Bandwidth yog ib qho khoom tawg. Yog li, yog tias cov ntaub ntawv xa mus rau yog ua sib zog, koj tuaj yeem xa ntau ntxiv rau hauv ib qho nqi ntawm lub sijhawm, thiab yog li txhim kho kev ua tau zoo. Txhawm rau lub suab digitized tsawg dua, nws yog compressed. Compression yog ib txoj hauv kev uas tib cov ntaub ntawv khaws cia tab sis siv qhov chaw tsawg zog (digital khoom). Thaum compression, cov ntaub ntawv yog tawm mus rau ib lub qauv (pob ntawv) kom zoo rau qhov compression algorithm. Cov ntaub ntawv muab xa tuaj yog xa tawm hauv lub network thiab thaum nws nce mus txog nws qhov chaw, nws yog decompressed rov qab mus rau nws lub xeev qub ua ntej tau hais. Feem ntau, tab sis, nws tsis yog qhov tsim nyog rau decompress cov ntaub ntawv rov qab, vim cov ntaub ntawv compressed twb nyob hauv lub xeev consumable.
Hom ntawm compression
Thaum twg cov ntaub ntawv raug muab khi, nws yuav lighter thiab kev pib ua haujlwm zoo dua. Txawm li cas los, nws nyhav yog qhov zoo tshaj plaws compression algorithms txo qhov zoo tshaj ntawm cov ntaub ntawv compressed. Muaj ob hom kev ywj pheej: tsis txawj thiab tsis muaj zog. Nrog compression compression, koj poob tsis muaj dab tsi, tab sis koj cant compress ntawd ntau. Nrog cov nyom los ntawm kev dag, koj ua tau zoo heev, tab sis koj poob hauv kev zoo. Koj feem ntau tsis tau txais cov ntaub ntawv muab cov ntaub ntawv rov qab mus rau nws lub xeev qub nrog cov qaug zog los ntawm compression, vim qhov zoo tau sacrificed rau qhov luaj li cas. Tab sis qhov no yog feem ntau ntawm lub sij hawm tsis tsim nyog.
Ib qho piv txwv zoo ntawm kev sib daj los yog MP3 rau suab. Thaum koj nquag suab, koj cant compress rov qab, koj MP3 audio yog twb zoo heev los mloog, piv rau cov ntaub ntawv ntshiab loj heev.
Encryption - decryption
Encryption yog ib qho ntawm cov cuab yeej zoo tshaj plaws rau kev ruaj ntseg. Nws yog txoj kev hloov cov ntaub ntawv rau hauv lub xeev tias nws tsis muaj leej twg nkag siab tau. Txoj kev no, txawm tias cov ntaub ntawv encrypted intercepted los ntawm cov neeg tsis tau tso cai, cov ntaub ntawv tseem nyob twj ywm tsis pub leej twg paub. Thaum cov ntaub ntawv encrypted ncav lub destination, nws yog decrypted rov qab rau nws thawj daim ntawv. Feem ntau, thaum cov ntaub ntawv muab luam tawm, nws twb yog encrypted rau ib yam twg, vim nws yog kho ntawm nws tus thawj lub xeev.
Mus rau qhov txuas rau ib daim ntawv teev cov qauv codecs uas siv rau VoIP .