Sound Sample Data

QuickTime Movie File Format Specification, May 1996

Sound Sample Data

The format of data stored in sound samples is completely dependent on the type of the compressed data stored in the sound sample description. The following sections discuss each of the formats supported by QuickTime.

Uncompressed 8-bit Sound

Eight-bit audio may be stored in either twos-complement or offset-binary encodings. In either case, if the data is in stereo, the left and right channels are interleaved.

Uncompressed 16-bit Sound

Sixteen-bit audio may be stored in either twos-complement or offset-binary encodings. However, twos-complement encoding is preferred. In either case, if the data is in stereo, the left and right channels are interleaved.

MACE 3:1 and 6:1

Not currently documented by Apple Computer. These are 8-bit formats.

IMA 4:1

The IMA encoding scheme is based on a standard developed by the International Multimedia Association for pulse code modulation (PCM) audio compression. QuickTime uses a slight variation of the format to allow for random access. IMA is a 16-bit audio format.

Law 2:1

The Law encoding scheme is used on North American and Japanese phone systems, and is coming into use for voice data interchange, and in PBXs, voice-mail systems, and Internet Talk Radio (via MIME). In Law encoding, 14 bits of linear sample data are reduced to 8 bits of logarithmic data.