Creative Voice file explained

VOC
Mime:	audio / x-voc
Developer:	Creative Technology

Creative Voice, filename extension .voc, is an audio format for digital audio data developed in the 1990s Sound Blaster sound cards from Creative Technology.

Construction

Original 8-bit format

The file format ^[1] ^[2] ^[3] consists of a 26-byte header and a series of subsequent data blocks containing the audio information. The byte order is little-endian.

VOC header!Offset (hex)!Length (in bytes)!Content
`0x00`	19	ASCII string`Creative Voice File`
`0x13`	1	`0x1A` (EOF)
`0x14`	2	Starting byte of first data block (usually `0x1A00` for a little-endian value of 26)
`0x16`	2	[Version] (major, minor), hexadecimal, e.g. `0x010a`, version 1.10
`0x18`	2	`Validation: ~version + 0x1234`, hexadecimal, truncated to 16 bits, e.g. `0x1129`

The header is followed by data blocks. Each data block begins with a type byte describing the contents of the data, followed by 3 bytes for the size of the data. For two of the 9 defined types, the subsequent size of the data is missing, so the block ultimately consists of only a single byte – these are 0x00 terminator, and 0x07 repeat end.

If a size is specified, the first 4 bytes will be followed by a block of the content resulting from the specified type with the specified size.

0x00 Terminator – –

0x01

English: Sound data

2 + size of the data

Audio content!Offset!Description!Meaning
`0x00`	Sampling rate	256-(1000000/sample rate)
`0x01`	Codec	see tableis ignored if a block of type `0x08` (extra info) defines a codec (from version 1.20)
from `0x02`	Audio data in the specified format (codec)

0x02 Sound continue Size of the data additional audio data in the same format as the previous block

0x03

Silence

Silence! Offset! Description! Meaning
`0x00-01`	Length of silence in the unit of the sampling rate	Integer `-1`
`0x02`	sampling rate	as with audio content

0x04 Marker 2 Marker number (2 bytes): remains in an intermediate memory during playback and can be jumped on again.

0x05 ASCII string Length of the string Null-terminated string

0x06 Repeat 2 Number of repetitions (2-byte integer) 0x0000to 0xFFFE1-65,535 repetitions, 0xFFFFfor infinite

0x07 End repeat – –

0x08 Extended 4 –

The file optionally ends with the terminator block (data block of type 0x00).

Use

Creative Voice files were used in various DOS games when they could use sound blaster cards for audio output, such as Eye of the Beholder.^[4]

The spread of the file format disappeared noticeably with the advent of RIFF WAVE, which was already supported in Windows. However, the Creative Voice file format required the installation of additional player programs included with the Sound Blaster Card drivers. With the advent of AC'97, WAVE, file extension .WAV, finally prevailed.

Notes and References

Web site: Greg figures out most of the .VOC Format. 2018-06-01. Greg. en. 2015-10-28. https://web.archive.org/web/20151028075631/http://www.textfiles.com/programming/FORMATS/vocform.pro. dead.
Web site: John chimes in with further analysis of the .VOC Format. 2018-06-01. John. en. 2015-10-28. https://web.archive.org/web/20151028075631/http://www.textfiles.com/programming/FORMATS/vocform2.pro. dead.
Web site: Audio File Formats FAQ. Chris . Bagwell. 2018-06-01. 1998-11-14. en. Chapter 11: File Formats. Documentation (FAQ) for the SoX audio editor
movAX13h. "Dr. Riptide Dissected" (README file). GitHub.