Format chunk (of a Wave file)

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

Description Length in bytes Starts at byte in the chunk Value
chunk ID 4 0x00 The ASCII character string "fmt " (note the space at the end)
size 4 0x04 The 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 code 2 0x08 Various. A typical compression code is 1, signifying uncompressed Pulse Code Modulation (PCM). Other values are shown below
number of channels 2 0x0A Various. The typical number of channels is 1 in mono waves and 2 in stereo waves
sampling rate 4 0x0C Various. An example sampling rate is 44100 = 0x0000AC44 for 44,100 Hz
average bytes per second 4 0x10 Various. 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 align 2 0x14 Various. 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 sample 2 0x16 Various. 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 bytes 2 0x18 Various. 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 bytes various 0x1A Various. 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 value Hexadecimal value Description
0 0x0000 Unknown
1 0x0001 Microsoft PCM (uncompressed)
2 0x0002 Microsoft ADPCM
3 0x0003 Microsoft IEEE float
4 0x0004 Compaq VSELP
5 0x0005 IBM CVSD
6 0x0006 ITU G.711 a-law
7 0x0007 ITU G.711 u-law
8 0x0008 Microsoft DTS
9 0x0009 DRM
10 0x000A WMA 9 Speech
11 0x000B Microsoft Windows Media RT Voice
16 0x0010 OKI-ADPCM
17 0x0011 Intel IMA/DVI-ADPCM
18 0x0012 Videologic Mediaspace ADPCM
19 0x0013 Sierra ADPCM
20 0x0014 Antex G.723 ADPCM
21 0x0015 DSP Solutions DIGISTD
22 0x0016 DSP Solutions DIGIFIX
23 0x0017 Dialogic OKI ADPCM
24 0x0018 Media Vision ADPCM
25 0x0019 HP CU
26 0x001A HP Dynamic Voice
32 0x0020 Yamaha ADPCM
33 0x0021 SONARC Speech Compression
34 0x0022 DSP Group True Speech
35 0x0023 Echo Speech Corp.
36 0x0024 Virtual Music Audiofile AF36
37 0x0025 Audio Processing Tech.
38 0x0026 Virtual Music Audiofile AF10
39 0x0027 Aculab Prosody 1612
40 0x0028 Merging Tech. LRC
48 0x0030 Dolby AC2
49 0x0031 Microsoft GSM610
50 0x0032 MSN Audio
51 0x0033 Antex ADPCM
52 0x0034 Control Resources VQLPC
53 0x0035 DSP Solutions DIGIREAL
54 0x0036 DSP Solutions DIGIADPCM
55 0x0037 Control Resources CR10
56 0x0038 Natural MicroSystems VBX ADPCM
57 0x0039 Crystal Semiconductors IMA ADPCM
58 0x003A Echo Speech ECHOSC3
59 0x003B Rockwell ADPCM
60 0x003C Rockwell DIGITALK
61 0x003D Xebec Multimedia
64 0x0040 Antex G.721 ADPCM
65 0x0041 Antex G.728 CELP
66 0x0042 Microsoft MSG723
67 0x0043 IBM AVC ADPCM
69 0x0045 ITU-T G.726
80 0x0050 Microsoft MPEG
81 0x0051 RT23 or PAC
82 0x0052 InSoft RT24
83 0x0053 InSoft PAC
85 0x0055 MP3
89 0x0059 Cirrus
96 0x0060 Cirrus Logic
97 0x0061 ESS Tech. PCM
98 0x0062 Voxware Inc.
99 0x0063 Canopus ATRAC
100 0x0064 APICOM G.726 ADPCM
101 0x0065 APICOM G.722 ADPCM
102 0x0066 Microsoft DSAT
103 0x0067 Microsoft DSAT-DISPLAY
105 0x0069 Voxware Byte Aligned
112 0x0070 Voxware ACB
113 0x0071 Voxware AC10
114 0x0072 Voxware AC16
115 0x0073 Voxware AC20
116 0x0074 Voxware MetaVoice
117 0x0075 Voxware MetaSound
118 0x0076 Voxware RT29HW
119 0x0077 Voxware VR12
120 0x0078 Voxware VR18
121 0x0079 Voxware TQ40
122 0x007A Voxware SC3
123 0x007B Voxware SC3
128 0x0080 Soundsoft
129 0x0081 Voxware TQ60
130 0x0082 Microsoft MSRT24
131 0x0083 AT&T G.729A
132 0x0084 Motion Pixels MVI-MV12
133 0x0085 DataFusion G.726
134 0x0086 DataFusion GSM610
136 0x0088 Iterated Systems Audio
137 0x0089 Onlive
138 0x008A Multitude, Inc. FT SX20
139 0x008B Infocom IT’S A/S G.721 ADPCM
140 0x008C Convedia G729
141 0x008D Congruency, Inc. (not specified)
145 0x0091 Siemens SBC24
146 0x0092 Sonic Foundry Dolby AC3 APDIF
147 0x0093 MediaSonic G.723
148 0x0094 Aculab Prosody 8kbps
151 0x0097 ZyXEL ADPCM
152 0x0098 Philips LPCBB
153 0x0099 Studer Professional Audio Packed
160 0x00A0 Maiden PhonyTalk
161 0x00A1 Racal Recorder GSM
162 0x00A2 Racal Recorder G720.a
163 0x00A3 Racal G723.1
164 0x00A4 Racal Tetra ACELP
176 0x00B0 NEC AAC NEC Corporation
255 0x00FF AAC
256 0x0100 Rhetorex ADPCM
257 0x0101 IBM u-Law
258 0x0102 IBM a-Law
259 0x0103 IBM ADPCM
273 0x0111 Vivo G.723
274 0x0112 Vivo Siren
288 0x0120 Philips Speech Processing CELP
289 0x0121 Philips Speech Processing GRUNDIG
291 0x0123 Digital G.723
293 0x0125 Sanyo LD ADPCM
304 0x0130 Sipro Lab ACEPLNET
305 0x0131 Sipro Lab ACELP4800
306 0x0132 Sipro Lab ACELP8V3
307 0x0133 Sipro Lab G.729
308 0x0134 Sipro Lab G.729A
309 0x0135 Sipro Lab Kelvin
310 0x0136 VoiceAge AMR
320 0x0140 Dictaphone G.726 ADPCM
336 0x0150 Qualcomm PureVoice
337 0x0151 Qualcomm HalfRate
341 0x0155 Ring Zero Systems TUBGSM
352 0x0160 Microsoft Audio1
353 0x0161 Windows Media Audio V2 V7 V8 V9 / DivX audio (WMA) / Alex AC3 Audio
354 0x0162 Windows Media Audio Professional V9
355 0x0163 Windows Media Audio Lossless V9
356 0x0164 WMA Pro over S/PDIF
369 0x0171 UNISYS NAP ULAW
370 0x0172 UNISYS NAP ALAW
371 0x0173 UNISYS NAP 16K
372 0x0174 MM SYCOM ACM SYC008 SyCom Technologies
373 0x0175 MM SYCOM ACM SYC701 G726L SyCom Technologies
374 0x0176 MM SYCOM ACM SYC701 CELP54 SyCom Technologies
375 0x0177 MM SYCOM ACM SYC701 CELP68 SyCom Technologies
376 0x0178 Knowledge Adventure ADPCM
384 0x0180 Fraunhofer IIS MPEG2AAC
400 0x0190 Digital Theater Systems DTS DS
512 0x0200 Creative Labs ADPCM
514 0x0202 Creative Labs FASTSPEECH8
515 0x0203 Creative Labs FASTSPEECH10
528 0x0210 UHER ADPCM
533 0x0215 Ulead DV ACM
534 0x0216 Ulead DV ACM
544 0x0220 Quarterdeck Corp.
560 0x0230 I-Link VC
576 0x0240 Aureal Semiconductor Raw Sport
577 0x0241 ESST AC3
592 0x0250 Interactive Products HSX
593 0x0251 Interactive Products RPELP
608 0x0260 Consistent CS2
624 0x0270 Sony SCX
625 0x0271 Sony SCY
626 0x0272 Sony ATRAC3
627 0x0273 Sony SPC
640 0x0280 TELUM Telum Inc.
641 0x0281 TELUMIA Telum Inc.
645 0x0285 Norcom Voice Systems ADPCM
768 0x0300 Fujitsu FM TOWNS SND
769 0x0301 Fujitsu (not specified)
770 0x0302 Fujitsu (not specified)
771 0x0303 Fujitsu (not specified)
772 0x0304 Fujitsu (not specified)
773 0x0305 Fujitsu (not specified)
774 0x0306 Fujitsu (not specified)
775 0x0307 Fujitsu (not specified)
776 0x0308 Fujitsu (not specified)
848 0x0350 Micronas Semiconductors, Inc. Development
849 0x0351 Micronas Semiconductors, Inc. CELP833
1024 0x0400 Brooktree Digital
1025 0x0401 Intel Music Coder (IMC)
1026 0x0402 Ligos Indeo Audio
1104 0x0450 QDesign Music
1280 0x0500 On2 VP7 On2 Technologies
1281 0x0501 On2 VP6 On2 Technologies
1664 0x0680 AT&T VME VMPCM
1665 0x0681 AT&T TCP
1792 0x0700 YMPEG Alpha (dummy for MPEG-2 compressor)
2222 0x08AE ClearJump LiteWave (lossless)
4096 0x1000 Olivetti GSM
4097 0x1001 Olivetti ADPCM
4098 0x1002 Olivetti CELP
4099 0x1003 Olivetti SBC
4100 0x1004 Olivetti OPR
4352 0x1100 Lernout & Hauspie
4353 0x1101 Lernout & Hauspie CELP codec
4354 0x1102 Lernout & Hauspie SBC codec
4355 0x1103 Lernout & Hauspie SBC codec
4356 0x1104 Lernout & Hauspie SBC codec
5120 0x1400 Norris Comm. Inc.
5121 0x1401 ISIAudio
5376 0x1500 AT&T Soundspace Music Compression
6172 0x181C VoxWare RT24 speech codec
6174 0x181E Lucent elemedia AX24000P Music codec
6513 0x1971 Sonic Foundry LOSSLESS
6521 0x1979 Innings Telecom Inc. ADPCM
7175 0x1C07 Lucent SX8300P speech codec
7180 0x1C0C Lucent SX5363S G.723 compliant codec
7939 0x1F03 CUseeMe DigiTalk (ex-Rocwell)
8132 0x1FC4 NCT Soft ALF2CD ACM
8192 0x2000 FAST Multimedia DVM
8193 0x2001 Dolby DTS (Digital Theater System)
8194 0x2002 RealAudio 1 / 2 14.4
8195 0x2003 RealAudio 1 / 2 28.8
8196 0x2004 RealAudio G2 / 8 Cook (low bitrate)
8197 0x2005 RealAudio 3 / 4 / 5 Music (DNET)
8198 0x2006 RealAudio 10 AAC (RAAC)
8199 0x2007 RealAudio 10 AAC+ (RACP)
9472 0x2500 Reserved range to 0x2600 Microsoft
13075 0x3313 makeAVIS (ffvfw fake AVI sound from AviSynth scripts)
16707 0x4143 Divio MPEG-4 AAC audio
16897 0x4201 Nokia adaptive multirate
16963 0x4243 Divio G726 Divio, Inc.
17228 0x434C LEAD Speech
22092 0x564C LEAD Vorbis
22358 0x5756 WavPack Audio
26447 0x674F Ogg Vorbis (mode 1)
26448 0x6750 Ogg Vorbis (mode 2)
26449 0x6751 Ogg Vorbis (mode 3)
26479 0x676F Ogg Vorbis (mode 1+)
26480 0x6770 Ogg Vorbis (mode 2+)
26481 0x6771 Ogg Vorbis (mode 3+)
28672 0x7000 3COM NBX 3Com Corporation
28781 0x706D FAAD AAC
31265 0x7A21 GSM-AMR (CBR, no SID)
31266 0x7A22 GSM-AMR (VBR, including SID)
41216 0xA100 Comverse Infosys Ltd. G723 1
41217 0xA101 Comverse Infosys Ltd. AVQSBC
41218 0xA102 Comverse Infosys Ltd. OLDSBC
41219 0xA103 Symbol Technologies G729A
41220 0xA104 VoiceAge AMR WB VoiceAge Corporation
41221 0xA105 Ingenient Technologies Inc. G726
41222 0xA106 ISO/MPEG-4 advanced audio Coding
41223 0xA107 Encore Software Ltd G726
41225 0xA109 Speex ACM Codec
57260 0xDFAC DebugMode SonicFoundry Vegas FrameServer ACM Codec
59144 0xE708 Unknown
61868 0xF1AC Free Lossless Audio Codec FLAC
65534 0xFFFE Extensible
65535 0xFFFF Development

See also:
Wave file format

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