VOC Format

VOC Format

Format type	Sound
Hardware	PCM
Number of sounds	1
Sampling rate	0 Hz - 4.2 GHz
Channel count	1 - 256
Bits per sample	0 - 255
Compressed?	Optional
Tags?	Text
Games	Boppin' Doom Duke Nukem II Duke Nukem 3D Dune II Eol! God of Thunder Highway Hunter Hocus Pocus In Search of Dr. Riptide King Arthur's K.O.R.T. Legend of Seven Paladins 3D Major Stryker Master of Orion Monster Bash Pee and Gity Prehistorik Rise of the Triad Realms of Chaos Sango Fighter Shadowcaster Shakii The Wolf Smashing Pumpkins Into Small Piles of Putrid Debris Wacky Wheels

The Creative Voice File (.voc) consists of a main header, followed by one or more data blocks. The file is in little endian format.

Main header

Data type	Name	Description
char[19]	signature	"Creative Voice File"
UINT8	signature2	0x1A
UINT16LE	size	Size of the main header. Usually 0x001A
UINT16LE	version	Version number. Usually 0x010A (0x0A 0x01) for the old format, or 0x0114 for the new format
UINT16LE	checksum	This should equal ~version + 0x1234

Data blocks

All data blocks have a common header:

Data type	Name	Description
UINT8	type	Block type
UINT24LE	len	Block size, excluding this four-byte header

There are 10 different block types:

0: Terminator

This special block does not contain a size in the header. It is used to indicate the end of the file, though the file can end without it.

1: Sound data with type

This block is generally only used in older files, and has been superceded by block #9.

Data type	Name	Description
UINT8	freq	Frequency divisor
UINT8	codec	Codec #, see below
BYTE[...]	data	Audio data

The sample rate of the file can be determined by:

Sample rate = 1000000 / (256 - frequency divisor)

The codec can be one of the following:

Codec #	Name
0x00	8 bits unsigned PCM
0x01	4 bits to 8 bits Creative ADPCM
0x02	3 bits to 8 bits Creative ADPCM (AKA 2.6 bits)
0x03	2 bits to 8 bits Creative ADPCM
0x04	16 bits signed PCM
0x06	alaw
0x07	ulaw
0x0200	4 bits to 16 bits Creative ADPCM. Only valid in block type 9

2: Sound data without type

This block is generally only used in older files, and has been superceded by block #9.

Data type	Name	Description
BYTE[...]	data	Audio data

This block uses the same codec as last set by block type 1.

3: Silence

Data type	Name	Description
UINT16LE	len	Length of silence - 1, in samples
UINT8	freq	Frequency divisor (see block type 1)

4: Marker

Data type	Name	Description
UINT16LE	value	Mark value

This marker can be picked up by the playback application to synchronize the sound file with an external animation, or to otherwise perform some action when the marker point has been reached.

5: Text

Data type	Name	Description
char[...]	text	Text string, null-terminated

6: Repeat start

This block signals the start of a repeated section. Blocks after this one, up until the next Repeat end block, will be repeated the number of times indicated.

Data type	Name	Description
UINT16LE	count	Number of times to repeat minus one (i.e. 0=repeat once, 1=repeat twice, etc.) 0xFFFF means repeat forever.

7: Repeat end

Like the terminator block, this block contains no data. It signals the end of the loop point, and if a loop is in progress, playback jumps back to the block following the most recent Repeat start block.

8: Extra information

This block is generally only used in older files, and has been superceded by block #9.

This block overrides the properties set by earlier blocks. Unlike block #1, this block allows the number of channels to be set, allowing stereo playback. It also increases the frequency divisor from a 8-bit value to 16-bits, allowing finer control of the final sampling rate.

Data type	Name	Description
UINT16LE	freq	Frequency divisor
UINT8	codec	Codec #, see below
UINT8	numChannels	Channel count minus one (0=mono, 1=stereo)

Unlike block #1, there is no audio within this block, so block #2 must be used to play audio with the options set here.

The sample rate of the file can be determined by:

Sample rate = 256000000 / ((numChannels + 1) * (65536 - frequency divisor))

9: Sound data (New format)

This block is (probably) only valid in files with a version >= 1.20 (0x114).

Data type	Name	Description
UINT32LE	rate	Sample rate
UINT8	bits	Bits per sample (e.g. 8 or 16)
UINT8	numChannels	Channel count (1 is mono, 2 is stereo)
UINT16LE	codec	Codec #
UINT32LE	reserved	Set to 0
BYTE[...]	data	Audio data

Source

This page was adapted from MultimediaWiki