Format chunk (of a Wave file)


The format chunk in the Wave file format has the following structure.

DescriptionLength in bytesStarts at byte in the chunkValue
chunk ID40x00The ASCII character string "fmt " (note the space at the end)
size40x04The size of the format chunk (number of bytes) less 8 (less the "chunk ID" and the "size"). The usual size of the format chunk is 16, unless there are any extra format bytes (see below)
compression code20x08Various. A typical compression code is 1, signifying uncompressed Pulse Code Modulation (PCM). Other values are shown below
number of channels20x0AVarious. The typical number of channels is 1 in mono waves and 2 in stereo waves
sampling rate40x0CVarious. An example sampling rate is 44100 = 0x0000AC44 for 44,100 Hz
average bytes per second40x10Various. For example, a PCM wave file that has a sampling rate of 44100 Hz, 1 channel, and sampling resolution of 16 bits (2 bytes) per sample, will have an average number of bytes equal to 44100 * 2 * 1 = 88,200
block align20x14Various. For example, a PCM wave that has a sampling resolution of 16 bits (2 bytes) and has 2 channels will record a block of samples in 2 * 2 = 4 bytes
significant bits per sample20x16Various. These bytes define the sampling resolution of the file. A typical sampling resolution is 16 bits per sample, but could be anything greater than 1
number of extra format bytes20x18Various. These bytes define the number of extra format bytes to follow in the format chunk. This field may or may not be present
extra format bytesvarious0x1AVarious. These may or may not be present

As with all information in wave files, data is stored little-endian. The number 88,200 = 0x00015888 will be stored as the byte sequence 0x88 0x58 0x01 0x00. Also, all information has to be word aligned (at every two bytes). If the audio data contains an odd number of bytes, it should be padded with a zero byte, although this byte will not be counted in the size variable.

A note on sampling resolution and data representation

By convention, (although different data representations are possible), when the sampling resolution of uncompressed PCM files (compression code 1) is 8-bit, the audio samples in the data chunk use unsigned integer numbers. Thus, audio samples range between 0 and 255 (0x00 and 0xFF) and silence is 127 (0x7F). When the sampling resolution of uncompressed PCM files is 16-bit or 24-bit, the audio samples in the data chunk are signed integers. Silence then is represented by 0. When the sampling resolution is 32-bit, the data would typically be signed floating point between -1 and 1 and silence would be 0.

Compression codes

A list of defined compression codes is as follows.

Decimal valueHexadecimal valueDescription
10x0001Microsoft PCM (uncompressed)
20x0002Microsoft ADPCM
30x0003Microsoft IEEE float
40x0004Compaq VSELP
50x0005IBM CVSD
60x0006ITU G.711 a-law
70x0007ITU G.711 u-law
80x0008Microsoft DTS
100x000AWMA 9 Speech
110x000BMicrosoft Windows Media RT Voice
170x0011Intel IMA/DVI-ADPCM
180x0012Videologic Mediaspace ADPCM
190x0013Sierra ADPCM
200x0014Antex G.723 ADPCM
210x0015DSP Solutions DIGISTD
220x0016DSP Solutions DIGIFIX
230x0017Dialogic OKI ADPCM
240x0018Media Vision ADPCM
250x0019HP CU
260x001AHP Dynamic Voice
320x0020Yamaha ADPCM
330x0021SONARC Speech Compression
340x0022DSP Group True Speech
350x0023Echo Speech Corp.
360x0024Virtual Music Audiofile AF36
370x0025Audio Processing Tech.
380x0026Virtual Music Audiofile AF10
390x0027Aculab Prosody 1612
400x0028Merging Tech. LRC
480x0030Dolby AC2
490x0031Microsoft GSM610
500x0032MSN Audio
510x0033Antex ADPCM
520x0034Control Resources VQLPC
530x0035DSP Solutions DIGIREAL
540x0036DSP Solutions DIGIADPCM
550x0037Control Resources CR10
560x0038Natural MicroSystems VBX ADPCM
570x0039Crystal Semiconductors IMA ADPCM
580x003AEcho Speech ECHOSC3
590x003BRockwell ADPCM
600x003CRockwell DIGITALK
610x003DXebec Multimedia
640x0040Antex G.721 ADPCM
650x0041Antex G.728 CELP
660x0042Microsoft MSG723
690x0045ITU-T G.726
800x0050Microsoft MPEG
810x0051RT23 or PAC
820x0052InSoft RT24
830x0053InSoft PAC
960x0060Cirrus Logic
970x0061ESS Tech. PCM
980x0062Voxware Inc.
990x0063Canopus ATRAC
1000x0064APICOM G.726 ADPCM
1010x0065APICOM G.722 ADPCM
1020x0066Microsoft DSAT
1030x0067Microsoft DSAT-DISPLAY
1050x0069Voxware Byte Aligned
1120x0070Voxware ACB
1130x0071Voxware AC10
1140x0072Voxware AC16
1150x0073Voxware AC20
1160x0074Voxware MetaVoice
1170x0075Voxware MetaSound
1180x0076Voxware RT29HW
1190x0077Voxware VR12
1200x0078Voxware VR18
1210x0079Voxware TQ40
1220x007AVoxware SC3
1230x007BVoxware SC3
1290x0081Voxware TQ60
1300x0082Microsoft MSRT24
1310x0083AT&T G.729A
1320x0084Motion Pixels MVI-MV12
1330x0085DataFusion G.726
1340x0086DataFusion GSM610
1360x0088Iterated Systems Audio
1380x008AMultitude, Inc. FT SX20
1390x008BInfocom IT’S A/S G.721 ADPCM
1400x008CConvedia G729
1410x008DCongruency, Inc. (not specified)
1450x0091Siemens SBC24
1460x0092Sonic Foundry Dolby AC3 APDIF
1470x0093MediaSonic G.723
1480x0094Aculab Prosody 8kbps
1510x0097ZyXEL ADPCM
1520x0098Philips LPCBB
1530x0099Studer Professional Audio Packed
1600x00A0Maiden PhonyTalk
1610x00A1Racal Recorder GSM
1620x00A2Racal Recorder G720.a
1630x00A3Racal G723.1
1640x00A4Racal Tetra ACELP
1760x00B0NEC AAC NEC Corporation
2560x0100Rhetorex ADPCM
2570x0101IBM u-Law
2580x0102IBM a-Law
2590x0103IBM ADPCM
2730x0111Vivo G.723
2740x0112Vivo Siren
2880x0120Philips Speech Processing CELP
2890x0121Philips Speech Processing GRUNDIG
2910x0123Digital G.723
2930x0125Sanyo LD ADPCM
3040x0130Sipro Lab ACEPLNET
3050x0131Sipro Lab ACELP4800
3060x0132Sipro Lab ACELP8V3
3070x0133Sipro Lab G.729
3080x0134Sipro Lab G.729A
3090x0135Sipro Lab Kelvin
3100x0136VoiceAge AMR
3200x0140Dictaphone G.726 ADPCM
3360x0150Qualcomm PureVoice
3370x0151Qualcomm HalfRate
3410x0155Ring Zero Systems TUBGSM
3520x0160Microsoft Audio1
3530x0161Windows Media Audio V2 V7 V8 V9 / DivX audio (WMA) / Alex AC3 Audio
3540x0162Windows Media Audio Professional V9
3550x0163Windows Media Audio Lossless V9
3560x0164WMA Pro over S/PDIF
3710x0173UNISYS NAP 16K
3720x0174MM SYCOM ACM SYC008 SyCom Technologies
3730x0175MM SYCOM ACM SYC701 G726L SyCom Technologies
3740x0176MM SYCOM ACM SYC701 CELP54 SyCom Technologies
3750x0177MM SYCOM ACM SYC701 CELP68 SyCom Technologies
3760x0178Knowledge Adventure ADPCM
3840x0180Fraunhofer IIS MPEG2AAC
4000x0190Digital Theater Systems DTS DS
5120x0200Creative Labs ADPCM
5140x0202Creative Labs FASTSPEECH8
5150x0203Creative Labs FASTSPEECH10
5280x0210UHER ADPCM
5330x0215Ulead DV ACM
5340x0216Ulead DV ACM
5440x0220Quarterdeck Corp.
5600x0230I-Link VC
5760x0240Aureal Semiconductor Raw Sport
5770x0241ESST AC3
5920x0250Interactive Products HSX
5930x0251Interactive Products RPELP
6080x0260Consistent CS2
6240x0270Sony SCX
6250x0271Sony SCY
6260x0272Sony ATRAC3
6270x0273Sony SPC
6400x0280TELUM Telum Inc.
6410x0281TELUMIA Telum Inc.
6450x0285Norcom Voice Systems ADPCM
7680x0300Fujitsu FM TOWNS SND
7690x0301Fujitsu (not specified)
7700x0302Fujitsu (not specified)
7710x0303Fujitsu (not specified)
7720x0304Fujitsu (not specified)
7730x0305Fujitsu (not specified)
7740x0306Fujitsu (not specified)
7750x0307Fujitsu (not specified)
7760x0308Fujitsu (not specified)
8480x0350Micronas Semiconductors, Inc. Development
8490x0351Micronas Semiconductors, Inc. CELP833
10240x0400Brooktree Digital
10250x0401Intel Music Coder (IMC)
10260x0402Ligos Indeo Audio
11040x0450QDesign Music
12800x0500On2 VP7 On2 Technologies
12810x0501On2 VP6 On2 Technologies
16640x0680AT&T VME VMPCM
16650x0681AT&T TCP
17920x0700YMPEG Alpha (dummy for MPEG-2 compressor)
22220x08AEClearJump LiteWave (lossless)
40960x1000Olivetti GSM
40970x1001Olivetti ADPCM
40980x1002Olivetti CELP
40990x1003Olivetti SBC
41000x1004Olivetti OPR
43520x1100Lernout & Hauspie
43530x1101Lernout & Hauspie CELP codec
43540x1102Lernout & Hauspie SBC codec
43550x1103Lernout & Hauspie SBC codec
43560x1104Lernout & Hauspie SBC codec
51200x1400Norris Comm. Inc.
53760x1500AT&T Soundspace Music Compression
61720x181CVoxWare RT24 speech codec
61740x181ELucent elemedia AX24000P Music codec
65130x1971Sonic Foundry LOSSLESS
65210x1979Innings Telecom Inc. ADPCM
71750x1C07Lucent SX8300P speech codec
71800x1C0CLucent SX5363S G.723 compliant codec
79390x1F03CUseeMe DigiTalk (ex-Rocwell)
81320x1FC4NCT Soft ALF2CD ACM
81920x2000FAST Multimedia DVM
81930x2001Dolby DTS (Digital Theater System)
81940x2002RealAudio 1 / 2 14.4
81950x2003RealAudio 1 / 2 28.8
81960x2004RealAudio G2 / 8 Cook (low bitrate)
81970x2005RealAudio 3 / 4 / 5 Music (DNET)
81980x2006RealAudio 10 AAC (RAAC)
81990x2007RealAudio 10 AAC+ (RACP)
94720x2500Reserved range to 0x2600 Microsoft
130750x3313makeAVIS (ffvfw fake AVI sound from AviSynth scripts)
167070x4143Divio MPEG-4 AAC audio
168970x4201Nokia adaptive multirate
169630x4243Divio G726 Divio, Inc.
172280x434CLEAD Speech
220920x564CLEAD Vorbis
223580x5756WavPack Audio
264470x674FOgg Vorbis (mode 1)
264480x6750Ogg Vorbis (mode 2)
264490x6751Ogg Vorbis (mode 3)
264790x676FOgg Vorbis (mode 1+)
264800x6770Ogg Vorbis (mode 2+)
264810x6771Ogg Vorbis (mode 3+)
286720x70003COM NBX 3Com Corporation
287810x706DFAAD AAC
312650x7A21GSM-AMR (CBR, no SID)
312660x7A22GSM-AMR (VBR, including SID)
412160xA100Comverse Infosys Ltd. G723 1
412170xA101Comverse Infosys Ltd. AVQSBC
412180xA102Comverse Infosys Ltd. OLDSBC
412190xA103Symbol Technologies G729A
412200xA104VoiceAge AMR WB VoiceAge Corporation
412210xA105Ingenient Technologies Inc. G726
412220xA106ISO/MPEG-4 advanced audio Coding
412230xA107Encore Software Ltd G726
412250xA109Speex ACM Codec
572600xDFACDebugMode SonicFoundry Vegas FrameServer ACM Codec
618680xF1ACFree Lossless Audio Codec FLAC

See also:
Wave file format

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