Audio Coding StandardsMPEGMPEG-1 Layer I, II & IIIMPEG-2 AACDolby AC-3MPEG-4Natural AudioMPEGAVS (Audio Video Standard)2.3

Contents 2.3.1 Overview of Audio Coding Standards 2.3.2 ITU-T Audio Coding Recommendations 2.3.3 Perceptual Audio Coding Basic 2.3.4 MPEG Audio Coding Systems 2.3.5 Dolby Audio Coding 2.3.6 China Audio Coding Initiatives 2.3.7 Next Step of Audio CodingReferences

ReferencesBasics about MPEG Perceptual Audio Codinghttp://www.iis.fraunhofer.de/amm/techinf/basics.html

MPEG _ Chinahttp://www.mpegchina.com.cn/index.htm

MPEG-4 Industry Forumhttp://www.m4if.org/

MPEG.ORGhttp://www.mpeg.org/MPEG/index.html

1. An Overview of Audio & Sound Coding Standards From Source Coding to Perceptual Coding Audio / Sound Coding Technologies Multimedia Communication Multimedia Framework

Audio Coding OverviewFrom source coding to perceptual codingPsychoacoustic ModelLow data rate, Hi-FiFrom signal to contentStructured Audio & Audio RetrievingFrom local application to global accessMPEG 21 perspectiveMultimedia FrameworkFrom stereo to surrounding multi-channelDolby AC-3 5.1 system & more

International ORG. / COM.International Telecommunication Unionhttp://www.itu.int/home/CCITTthe International Consultative Committee on Telephony and TelegraphyInternational Organization for Standardizationhttp://www.iso.org/International Electrotechnical Commissionhttp://www.iec.org/MPEGMoving Picture Experts Group http://mpeg.telecomitalialab.com/

Dolby Laboratories, Inc.http://www.dolby.com/ http://www.dolby.com.cn/

2. ITU Recommendations G.711-PCM G.721-32kbit/s G.722-64kbit/s(7KHz) CELP-16kbit/s ITU

Chronicle1972G.711 64kb/s A PCM 1984G.721 32kb/s ADPCM G.722 64kb/s ADPCM G.723.1 5.3kb/s6.3kb/s LSF G.726 16kb/s1990G.727 16-40kb/s ADPCM1992G.728 / G.729 16kb/s LD-CELP1988RPE-LTP 13kb/sGSM1989VSELP 6.7kb/s

ITU Recommendations

PCM64kb/sG.711ISDN4.04.5(A)(A)APCMDPCMADPCM32kb/sG.72 1SB-ADPCM64kb/sG.722G.726G.727LPC2.4kb/s2.53.5

ITU RecommendationsG.711PCM8000Hz8AA 13PCMA14PCM8G.721198664kbit/sAPCM32kbit/s ADPCMPCM

ITU RecommendationsADPCM/ APCMPCMPCM415(15)04 PCMAPCM(synchronous coding adjustment)()

3. Preliminary for Perceptual Audio Coding(Psychoacoustic Model)(Perceptual Sub-band Coding)Dolby AC-3/MPEG Audio Coding

Some Conceptions( dyn/cm2 )( W/cm2 )(dB)10-16 W/cm2 = 0 (dB)( phon ) ( sone ) = 0 () ( Hz ) Mel ()Mel = 1000 Log2(1+)

Perceptual Audio Coding (1)HzdB 1 kHz120dB()1202 kHz4 kHz

Perceptual Audio Coding (2) 20 Hz18000 Hz40 dB

Perceptual Audio Coding (3)(masking tone)(masked tone)

(Frequency Domain Masking)(Simultaneous Masking)

(Time Domain Masking)

Perceptual Audio Coding (3 cont.)

Perceptual Audio Coding (3 cont.)250 Hz1 kHz4 kHz8 kHz = 0.25, 1, 4 kHz

Perceptual Audio Coding (3 cont.)(Critical Band)20 Hz16 kHz24

Bark ()1 Bark = () < 500 Hz, 1 Bark /100 () > 500 Hz, 1Bark 9 + 4log( /1000)

Perceptual Audio Coding (3 cont.)

(pre-masking)(post-masking)

520 ms50200 ms

Perceptual Audio Coding (3 cont.)Audio Masking

4. MPEG Audio MPEG-1 Audio : Layer I, II &III MPEG-2 Audio : Back Compatible (BC)AAC : Advanced Audio Coding (Non BC) MPEG-4 Audio : Overview MPEG 21 : The Next Step of MPEGMoving Picture Experts Group Audio Coding Standards

About MPEGISOIEC WG111986MPEGMPEGMPEG MPEG-11992MPEG-2MPEG-319927(High-Definition TVHDTV)MPEG-4(1999)MPEG-5MPEG-6MPEG-7()

Chronicle of MPEG StandardsMPEG Audio Coding Standards199308 MPEG-1 ISO/IEC 11172199408 MPEG-2 ISO/IEC 13818199901 MPEG-4 ISO/IEC 14496 V1.0199912 MPEG-4 ISO/IEC 14496 V2.0199810 MPEG-7 200107 200109 200003 MPEG-21

Some ExplanationsMPEG-1 ISO/IEC 11172 MPEG-2 ISO/IEC 13818MPEG-4 ISO/IEC 14496 V1.0MPEG-4 ISO/IEC 14496 V2.0(video object)MPEG-7

Some Explanations (cont.)MPEG Audio(2 kHz5 kHz)()

Prices Aspects MPEG-LAMPEGMPEG-LAMPEGMPEG-LAWhyPrice ?MPEG 4

4. MPEG Audio MPEG-1 Audio : Layer I, II &III MPEG-2 Audio : Back Compatible MPEG-2 AAC : Advanced Audio Coding MPEG-4 Audio : OverviewMoving Picture Experts Group Audio Coding Standards

4. MPEG Audio MPEG-1 Audio : Layer I, II &III MPEG-2 Audio : Back CompatibleAAC : Advanced Audio Coding MPEG-4 Audio : OverviewMoving Picture Experts Group Audio Coding Standards

4. MPEG Audio MPEG-1 Audio : Layer I, II &III MPEG-2 Audio : Back CompatibleMPEG-2 AAC : Advanced Audio Coding MPEG-4 Audio : OverviewMoving Picture Experts Group Audio Coding Standards

4. MPEG Audio MPEG-1 Audio : Layer I, II &III MPEG-2 Audio :Back CompatibleAAC : Advanced Audio Coding MPEG-4 Audio : OverviewMoving Picture Experts Group Audio Coding Standards

MPEG-1 AudioAudio Coding Algorithms(sub-band codingSBC)SBCMPEGMPEG48 kHz16256 kb/s61 (40 kHz44.1 kHz)

MPEG-1 Audio (cont.)MPEG Audio ISO/IEC 11172-3

MPEG-1 Audio (cont.)/

Layer I, II & III

MPEG-1 Audio (cont.)CD*MUSICAM ( Masking pattern adapted Universal Sub-band Integrated Coding And Multiplexing ) **ASPEC ( Adaptive Spectral Perceptual Entropy Coding of high quality musical signal ) ()

MPEG-1 Audio (cont.)MPEG /

CRC MPEG

MPEG-1 Audio (cont.)(Layer III)

MPEG-1 Audio (cont.)-()(masking threshold)

(signal-to-mask ratioSMR)

(frame)

MPEG-1 Audio (cont.)32

MPEG-1 Audio (cont.)MPEG31231SBCSBCSBC (frame)Layer I 384 3212Layer II Layer III 1152

MPEG-1 Audio (cont.)

MPEG-1 Audio (cont.)Layer I1-DCT (discrete cosine transform)SMR 6(scale factor)SMR(bit allocation)

MPEG-1 Audio (cont.)Layer I(12) MUX

32

CRC16

4

6

MPEG-1 Audio (cont.)Layer II13111521 23 1(12)

MPEG-1 Audio (cont.)Layer III (Huffman)ASPEC (Audio Spectral Perceptual Entropy Encoding)OCF (Optimal Coding In The Frequency domain)12123(modified discrete cosine transformMDCT)12MDCT3

Layer IIIISO/MPEG Audio Layer III Coder / Decoder

MPEG-1 Audio (cont.)MPEG3

MPEG-2 Audio OverviewMPEG

MPEG-2 AudioMPEG-2 MultichannelMPEG-1 AudioMPEG-2 BC (Backward Compatible)MPEG-2 AAC (Advanced Audio Coding)MPEG-1MPEG-2 NBC (Non-Backward Compatible)

MPEG-2 Audio : BC

MPEG-2 BCISO/IEC 13818-3MPEG-2 BCMPEG-1 Audio (ISO/IEC 1117-3)-1, -2-316 kHz, 22.05 kHz24 kHz32384 kb/s8640 kb/s5.17.1Linear PCM(PCM)Dolby AC-3(Audio Code Number 3)

MPEG-2 BCMPEG-2 BC

MPEG-2 BC Multichannel5.13/2-LFE.1LFE3()2LFE (low frequency effects3Hz~120Hz) 7.15.1 5.1

MPEG-2 BC ISO/IEC 13818-3

MPEG AAC MPEG-2 AAC MPEG-2 AAC MPEG-2 AAC

MPEG-2 AACMPEG-2 AACMPEG-2MPEG-2 AACAAC8 kHz96 kHzAACAAC4816LFE (low frequency effects)16(overdub channel)(multilingual channel)16MPEG-2 AAC11:1(44.116 )/11=64 kb/s5320 kb/sMPEG2MPEG-2 AAC1MPEG370

MPEG-2 AAC MPEG-2 AACMPEG AudioAACAAC(advanced audio coding tools)(modular)(tool)AAC

(Main Profile)(Gain Control)AACAAC

(Low Complexity Profile)(temporal noise shapingTNS)(Scalable Sampling Rate Profile)TNS

MPEG-2 AAC (Gain control)PQF (polyphase quadrature filter)(gain detector)(gain modifier)4PQF(Filter Bank)MPEG-2 AACMDCTTDAC(time domain aliasing cancellation)

MDCTKBD (Kaiser-Bessel derived)(sine)MDCT

MDCT

n N i =

TNSTNSTNS(joint stereo coding)MPEG-2 AACM/S(Mid/Side encoding)/(Intensity /Coupling)M/SM/S(matrixed stereo coding)M/SM(middle)S(side)M/S-(sum-difference coding)/(intensity stereo coding)(channel coupling coding)(irrelevance)

(Prediction)(stationary)(Quantizer)(Noiseless coding)

MPEG-2 AAC

MPEG-4 AudioMPEG-4 Audio(parametric coding)(code excited linear predictiveCELP)/T / F (time / frequency)SA (structured audio)-TTS (text-to-speech)

MPEG-42 kb/s64 kb/s(natural audio)MPEG-48 kHz(speech)24 kb/s8 kHz16 kHz(audio)416 kb/s CELPCELP(code excited linear predictive)624 kb/s8 kHz16 kHzT/F-(time-to-frequencyT/F)(vector quantizationVQ)16 kb/s8 kHz

MPEG-4 Audio* UMTS (universal mobile telecommunication system)

MPEG-4TTSMIDI-Text-to-Speech

5. Dolby Audio CodingOverview of Dolby Audio Coding SystemAC-1 : Dolbys first digital coding systemAC-2 : 2-channel stereo systemDolby AC-3 : Multi-channel Digital Audio Compression System

Brief HistoryAC-1 (1987)Dolbys first digital coding systemSimple delta modulation based coding techniques4-2-4 multi-channel system, 2-1 bit-rate reductionAC-2 (1989)TDAC (Time Domain Aliasing Cancellation) Filter Bank based on MDCT/MDST2-channel stereo systemBit allocation based on Psychoacoustic ModelAC-2a : pre-echo control by block size adaptation

Brief HistoryAC-3 (1991~)TDAC Filter Bank based on MDCT5.1 multi-channel (320 kb/s) digital audioUSA HDTV Digital Audio Coding StandardFirst cinema demonstration : Star Trek VIChannel coupling techniques is applied to reduce bit-rate at high frequencies

AC-3 IntroductionInput Audio : 1 ~ 5.1 channels of source0.1 channel : low frequency (Subwoofer) signalsampling rate : 32 kHz, 44.1 kHz, 48kHzwindowing : 50% overlap/add Fielder windowBit Rate : 32 kb/s ~ 640 kb/sbandwidth reduction factor : 13.5uncompressed PCM sample : 6 channel * 48 kHz * 18 bits = 5.184 Mb/sstandard bit rate : 384 kb/s

AC-3 FeaturesAC-3 Encoder

AC-3 FeaturesAC-3 Decoder

AC-3 FeaturesBit-stream Syntax1 Frame represents 1536 PCM samples for all channels

1 Block represents 256 PCM for each channelSI=Sync. Info BSI=Bit-stream Info CRC for error correction Aux Data for private control

AC-3 FeaturesThe AC-3 Multi-channel CoderThe Conception of Multi-channel

6. Audio Coding Initiatives in China An Overview of Chinese AVS Project Audio Coding Quality Assessment Methods

China AVS ProjectAVS : audio video coding standard ()2002 621 Official Homepage : http://www.avs.org.cn

7. Next Step of Audio Coding Standardization MPEG 21:(Multimedia Framework)

Next StepMPEG-7MPEG-21MPEG62MPEG28JPEG2002102125

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MIDIWAVE MIDI MIDIMic CD 5KB3.6MB 5242

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FMFM,, ()

FM(cont.)(Yamaha OPL-III)

FM1314ROMROMFM

FM 44.1 kHz16CD-DAROM

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MIDIMIDIMIDIMIDIMIDIMIDI(local control)

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MIDI(cont.)MIDIMIDI(MIDI channel)16

MIDI(cont.)MIDI

MIDI(cont.)PCMIDIMIDIPCMIDIMIDIIN

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MIDI(cont.) 33()63998

MIDIMIDI82(All MIDI status byte and data byte values are in hexadecimal )21n 0~F

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MIDI(cont.) MIDI

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2MIDIMIDI