MPEG2_intro_v02_GB

1、MPEG2 / DVB概述1數(shù)字與模擬的比照模擬有限的帶寬1 個(gè)頻道l = 1 個(gè)電視節(jié)目多種標(biāo)準(zhǔn)PalSecamNTSC有限的質(zhì)量復(fù)合視頻 (減少色度 resolution)數(shù)字增加的帶寬1 頻道 = 多達(dá) 12 個(gè)電視節(jié)目單一標(biāo)準(zhǔn)DVB新的電視業(yè)務(wù)互動(dòng)電視按次付費(fèi)PPV視頻點(diǎn)播VOD改進(jìn)的質(zhì)量復(fù)合視頻 (no cross color effect)立體聲音頻和環(huán)繞立體聲2視頻數(shù)字化3CCIR 601 建議書模擬視頻信號傳達(dá)了許多信息，例如:水平同步垂直同步Test linesCCIR 601 標(biāo)準(zhǔn)定義了如何使用對運(yùn)動(dòng)的視頻進(jìn)行編碼8bits 亮度和色度，根據(jù)4:2:2格式與625/50 和

2、 525/60 標(biāo)準(zhǔn)兼容與以上兩個(gè)標(biāo)準(zhǔn)的采樣數(shù)相同4Active Field1Active Field2VBI Field 1VBI Field 2HANCField288 lines240 lines288 lines240 lines24 lines25 lines625 lines525 lines2720 samples(720 Y + 2360 Cr,Cb)2144 samples非壓縮數(shù)字視頻 4 : 2 : 2YCrCb13.5 MHz6.75 MHz6.75 MHz復(fù)合27 MHzx10 bits/采樣 = 270 Mbit/sx8 bits/采樣 = 216 Mbit/s16

3、6 Mbit/s active5A:B:C Notation6DVB 標(biāo)準(zhǔn)DVB-S衛(wèi)星數(shù)字傳送系統(tǒng)DVB-C有線數(shù)字傳輸系統(tǒng) DVB-T地面數(shù)字播送系統(tǒng)DVB-SI業(yè)務(wù)信息標(biāo)準(zhǔn)DVB-CA條件接收通用接口DVB-RC有線電視系統(tǒng)回傳通道其他7MPEG 概述MPEG : 運(yùn)動(dòng)圖像專家組, 創(chuàng)立于 1988MPEG Group 負(fù)責(zé)音頻和視頻壓縮標(biāo)準(zhǔn)的制定199219941996JPEG : CCITT 建議書 H261 靜態(tài)圖像 DCT 轉(zhuǎn)換 Huffman 編碼 可變比特率 (Openloop)MPEG-1 : ISO/CEI 11172 視頻 JPEG 功能 1.5 Mb/s max On

4、ly SIF (360 x 288) 媒體存儲MPEG-2 : ISO/CEI 13818視頻 MPEG1 兼容 10Mb/s HD 格式 廣播目的8MPEG 2普通標(biāo)準(zhǔn)視頻編碼 (ISO/IEC 13818-2)音頻編碼 (ISO/IEC 13818-3)系統(tǒng) (ISO/IEC 13818-1)應(yīng)用多樣性紀(jì)錄和存儲 : Beta SX, DVD播送 : DVB網(wǎng)絡(luò)傳送 : ATM格式兼容性采樣率 : 4:4:4, 4:2:2, 4:2:0分辨率 SIF to HDTV逐行和隔行掃描Mutiscale extensionprovides multiquality transmission :

5、basic + enhanced9MPEG 采樣模式F1/L1F2/L1F1/L2F2/L2Fn/Ln : Frame/lineCB, CR samplesY sample4:4:4 采樣(24 bits / pixel)F1/L1F2/L1F1/L2F2/L24:2:2 采樣(16 bits / pixel)F1/L1F2/L1F1/L2F2/L24:2:0 采樣10Principe du traitement intra-trame (JPEG)原始圖像Yu,vYQu,vYZZxYRLCx壓縮的圖像72727273737472727372726975757466DCT量化Zig-Zagsc

6、anCodage longueur variableCodage entropique57114-23-5-1-1-1300000-1036100-1000000000003610-100036012-100100110101111010.Bloc11空間相關(guān) : DCT離散余弦變換 系數(shù)Maximum energy DC component mean block value像素塊以它所在的空間位置的亮度值表示Matrix of DCT coefficientsrepresenting frequency components in theblockMinimum energy maximum

7、 spatialfrequencyHorizontal frequencyVertical frequency12時(shí)間相關(guān) : 運(yùn)動(dòng)補(bǔ)償InterpolationMotionvectorBBIP13MPEG 視頻序列的層 / 時(shí)間圖像(p slices)Slice(n macroblocks)宏塊(4 blocks)塊(8 x 8 pixels)II圖像組 (GOP)序列14圖像組 : GOPM = 3 imagesN = 12 imagesI1B2B3P4P7B5B6P10B8B9B11B12I13forward predictionbidirectional predictionIntra

8、 Images (I) : 參考圖像, 用 DCT編碼Predicted Images (P) :使用前面的圖像編碼(I or P) ，使用運(yùn)動(dòng)補(bǔ)償向量Bidirectional images (B) :使用前面和后面圖像進(jìn)行插值 (I or P)15圖像順序I1B2B3P4P7B5B6I10B8B9B11B12P13I1B-1B0P4P7B2B3I10B5B6B8B9P13表示順序傳送順序圖像組 (N=10 / M=3)16MPEG 視頻編碼器框圖Source pictureQuantizationstep預(yù)處理(Format, picture ordering)DCTQMux& VLCBu

9、fferEncodedpicturePredictionerrorIDCTIQIntra/Inter/Bidir.modesDecision0motionvectorsMotioncompensationPicturememoryMotionestimationPrediction17MPEG-2: Profiles & LevelsMPHLMPH14LMPMLSPMLSNRPMLSSPH14LHPHLHPH14LHPMLMPLLSNRPLL18視頻流緩沖I0P3B1B2P6B4B5P9B7B8I12Buffer levelTimeMaxI,P,BEncodingBufferBit Rate

10、CTRLBufferI,P,BDecodingSource PicturesVideo Stream(constant bit rate)Decoded PicturesI10Decoding Time (DTS)Presentation Time (DTS)CoderDecoder19MPEG 音頻 : the digital chainFILTER(BWKHz)ADCFe 2BWKHz(采樣頻率)QUANTIZING&CODINGS(t)S(n)FeDECODINGS(t)S(n)STORAGEMEMORYBit Rate 采樣 : 16 bits 頻率 : 32, 44.1, 48KHz

11、 信噪比 : 96dB 頻帶寬度 : 15/20KHz 比特率 : 2x768kb/s數(shù)字音頻磁帶 采樣 : 16 bits 頻率 : 44.1KHz 信噪比 : 96dB 頻帶寬度 : 15/20KHz 比特率 : 2x705.6kb/sCD光盤DAC20MPEG 音頻 : 量化錯(cuò)誤S(t)tS(t)tt BW/2模擬信號數(shù)字信號Vt The sampling process introduces the Quantizing NoiseQuantizing noise (SNR) = 6.02n + 1.76 dBex : SNR = 98.1dB for a 16 bit system0

12、00001010011100QuantizingInterval QMax. error : +/- Q/221MPEG 音頻 : 16位采樣的量化噪聲-10dB-50dB-100dB頻率 (kHz)音頻信號頻譜-140dB量化噪聲5101520信噪比(SNR) = 6x16 = 96 dB22MPEG 音頻 : 3位采樣的量化噪聲-10dB-50dB-100dBFrequency (kHz)音頻信號頻譜-140dB5101520量化噪聲可聽見的噪聲 !信噪比(SNR) = 6x3 = 18 dB23MPEG 音頻 : 心理聲學(xué)模型 (1)020406080dB可聞?dòng)蛟诎察o環(huán)境下的可聞?dòng)?05

13、01005001K2K5K10K20Kf(Hz)不可聞的可聞的24MPEG 音頻 : 心理聲學(xué)模型 (2)020406080dBThreshold of audibilityThreshold of audibilityat silence20501005001K2K5K10K20Kf(Hz)pure 1Khz sinusmasking threshold25MPEG 音頻 : 量化錯(cuò)誤的調(diào)整-10dB-50dB-100dB頻率 (kHz)Masking Threshold音頻信號頻譜THE QUANTIZING ERROR IS ADJUSTED FOR EACH SUB-BAND750 H

14、z024KHz26MPEG音頻 : BIT ALLOCATION-10dB-50dB-100dBFrequency (kHz)5 bits2 bits0 bitSUB-BAND BIT ALLOCATIONSCALE FACTOR (maximum value during 8ms)TOTAL DESIRED BIT RATETHE ALLOWED QUANTIZING NOISE 27Principle behind the MPEG-1 audio encoderPsycho-acoustic model32 filterbankMultiplexerControlMPEGaudiostr

15、eam PCMinputLRQ1Q32Q3Q2Quantisation28MPEG-2 (MPEG-1 兼容)環(huán)境 編碼/解碼原理MatrixMPEG-1audiodata Left LRight RCoderLeft surround LSCentre CRight surround RSMPEG-1encoderMPEG-2extensionencoderMPEG-2auxiliarydata TransmissionL0R0T3T4T529MPEG 音頻: 音頻包30MPEG 2 層次結(jié)構(gòu)31MPEG2 節(jié)目與傳送流復(fù)用Program streamPS MuxProgramme NVid

16、eo coderISO/IEC 13818-2Audio coderISO/IEC 13818-3Time baseSTC NVideo coderISO/IEC 13818-2Audio coderISO/IEC 13818-3Time baseSTC 1PacketizerPacketizerTSMuxSystem coderISO/IEC 13818-1Programme 1Transport streamHard diskQuasi error-free mediaDVDError-prone mediaVideo dataAudio dataVideo dataAudio dataP

17、ES VideoPES AudioPCRPacketizerPacketizerPES VideoPES Audio32打包的根本流(PES)的創(chuàng)立830 kbytes830 kbytes830 kbytes830 kbytesMPEG-2 編碼打包有效負(fù)荷包頭源視頻打包的基本流fixed lengthPresentation Units(uncoded pictures)variable lengthAccess Units(coded pictures)fixed or variable length PES packets33PES的組成 (main fields)MPEG-2 PES1

18、011.1100 : PSM1011.1101 : private data T11011.1110 : Padding stream1011.1111 : private data T2 110 x.xxxx : audio (1 to 32)1110.xxxx : video (1 to 16)1111.0000 : ECM1111.0001 : EMM.Stream id (8)包起始碼stream idPES 包長可選的l PES 包頭PES 包數(shù)據(jù)包頭有效負(fù)荷10PES scrambling controlPES prioritydataalignmentindicatorcopyr

19、ightoriginalor copy7flagsPES headerdata lengthoptionalfieldsstuffingbytes(0 xFF)E.g. stuffing bytes incase of PES at fixedlength)PTSDTSESCRESrateDSMtrick modeadditional copy infoPreviousPES CRCPES extensionPES extensionfield lengthP-STDbufferscale & sizeprogram packetseq entrpackheaderlengthPESpriva

20、te dataPES extensionfield dataoptional fields5flags00 : no scrambling01 : no scrambling 10 : scrambling with an even control word11 : scrambling with an odd control word (hierarchical system forexample)Bit rate of PESPresentation and decodingtime stamps expressed in 90 KHz clock periods(maximum dela

21、y between 2broadcast = 0.7 s)packet start code prefixstream idpacket lengthSTD Buffer scale & size PTSDTSstuffing bytes data bytesMPEG1 PES00.00.01h34TS 包的構(gòu)建PES 包TS 包填充域(填充字節(jié))188 bytes(包頭 + 有效負(fù)荷)35MPEG2 Transport Stream Paquets36MPEG2 傳送流語法1 if the payload information is erroneous.Example: demodulat

22、ed signal (QPSK), when the external code (RS) and internal code (convolutive) are not able to correct the errors.包頭adaptationfield (*)payload188 BytesStuffing at case of TS endsplicetypepiecewiserate ItwoffsetItw_validflagDTS_next_au00 : No scrambling01 : Scrambling the default control word10 : Scra

23、mbling an even control word11 : Scrambling an odd control word the same as the PES onesyncbytetransport errorindicatorpayloadunit startindicatortransport priorityPIDtransportscramblingcontroladaptation fieldcontrolcontinuitycounterPCR counterIdentifier of the component defined by the operator.PID=0

24、(PAT table) andPID=0 (CAT table) are reserved values.1 if the payload begins:with a PES start (the PES 1st byte has to begin at a payload start).with a PSI table start.Payload begins with a pointer-field which indicates the position of the PSI table 1st byte.47hoptionalfieldsstuffingbytes5flagseleme

25、ntarystream priorityindicatorrandomaccessindicatordiscontinuityindicatoradaptationfieldlength(*): non systematicPCROPCRsplicecountdowntransportprivate data lengthoptional fields3flagsadaptationfield datalengthtransportprivate data length37節(jié)目參考時(shí)鐘 (PCR)PCR is used to recover the program encoding clock

26、 at the decoder sitePCR are generated for each program stream, and the TS packet which carry the PCR are identified in the PMT table, with a specific PID (PCR_PID)PCR_Base consists of 33 bits (n x 90 kHz)PCR_Extension consists of 9 bits (m x 27 MHz) PCR is inserted into the Adaptation field of some

27、TS packets (at least every 0.1 seconds)At any time the TS stream is modified, PCR must be updated !27 MHzPCRStreamEncoder Time Stamps InsertionVCXO(27 MHz)PCRStreamDecoder program clock recoveryPCRProcessingDVBChain38MPEG2-PSI : Program Specific Information (2)neverencryptedUsuallyencrypted1 or seve

28、ral sectionsPID 0PID 0PID 1PID 10PID 10PID 32PID 1201 or several sectionsPAT(PID 0)ServicesPID ofPMTService 0Service 1Service 2Service 7103268147NIT(PID 10for example)Private dataCAT(PID 1)CAPIDCA syst 1 CA syst 2 CA syst 31201301401 sectionPMT of service 1(PID 32)ComponentsPIDVideo CA_Descriptor.Au

29、dio (F) CA_Descriptor.Audio (E)Audio (G)Sub-title730129501315257103PID 120 = EMM syst 1PID 32 = PMT service 1+ PMT descriptors1 or several sections39DVB-SI : 網(wǎng)絡(luò)與復(fù)用概念TSTSTSTSTSTSTSTSTSTSTSTSffTSTSTSTSTSTSf36 MHz Transponders8 MHz channels8 MHz channelsSatelliteCableTerrestrialNetworksMultiplexesServi

30、cesBouquetComponents40DVB 條件接收加擾器ECM發(fā)生器EMM發(fā)生器解擾器CW發(fā)生器ECM接收EMM接收ECM控制層EMM管理層CW（控制字）CW（控制字）業(yè)務(wù)數(shù)據(jù)業(yè)務(wù)數(shù)據(jù)業(yè)務(wù)密鑰- 業(yè)務(wù)密鑰- 接收條件- 業(yè)務(wù)密鑰- 管理密鑰- 用戶權(quán)限- 管理密鑰- 用戶權(quán)限41EMM 和 ECM 在傳送流中發(fā)現(xiàn)的處理方法Prog 3Prog 3PID 0Video 3PID MECM-3EMM-1PID 1Video 3Audio 3EMM-2CA System 1CA System 2EMM-1 referenceEMM-2 referenceCATsectionsPATsect

31、ionsPMTsectionsPIDAudioVideoECMPCRPID M傳送流42信息管理系統(tǒng)4355 Mb/s27.5 MHz(x 2)(x 1.28)35.2 MHz38 Mb/s41.25 Mb/s(TS=188 TS with RS = 204)(Puncturing 3/4)Channel EncodingQPSK Modulation MPEG-2/DVBSignalIF70 MHzBW = 35.2 MHz1/2 Nyq.FiltersD/AD/AQPSKmodulationEnergy dispersal(PRBS)Outercoding(RS)InterleavingI

32、nner coding(convolutionand puncturing)7 Mb/s8 MHz38 Mb/s42 Mb/sroll-off = 0.15MPEG-2/DVBSignalIFBW = 8 MHzDifferentialencodingD/AD/AQAMmodulationEnergy dispersalRSInterleavingByte to symbolConversionChannel EncodingPhysicalInterfaceClockDataQAM ModulationI, Qseparation1/2 Nyq.FiltersLOValues (exampl

33、e)信道編碼和調(diào)制衛(wèi)星調(diào)制Cable 調(diào)制44調(diào)制 : 64 QAM45調(diào)制: 調(diào)制質(zhì)量46有線調(diào)制: 比特率47完整的DVB傳送和接收鏈Programme 1MPEGcodingMultiplexing+ scramblingFEC, formattingfiltering, DACQAM or QPSKmodulationPESMPEGcodingMPEGdecodingDescrambling + demultiplexingADC, filtering, formatting, FECQAM or QPSKdemodulationUp-conversion, amplification

34、CABLE or SATELLITEAmplification down-conversionProgramme nPictureSoundPES188 bytepacket188 bytepacket112I, QIFPESIFI, QChannel coding/decoding345678910Source coding/decodingSelection48DVB-S 典型系統(tǒng)結(jié)構(gòu)UpLink Station Satellite OperatorQPSK ModulatorQPSK ModulatorQPSK ModulatorDigital Broadcasting CentreMPEGASIRouterOPEN TVServerATMTXATMRXNVODServerATMTXOFDMReceiverDescramblerQPSK ReceiverDescramblerPLAY OUTCENT