In order to support a broad range of audio data formats, the Movie Toolbox can accommodate a number of different sample encoding formats, sample sizes, sample rates, and compression algorithms. The following paragraphs discuss the details of each of these attributes of movie sound data. Offset-binary encoding represents the range of amplitude values as an unsigned number, with the midpoint of the range representing silence. Samples in Macintosh sound resources are stored in offset-binary form. The Movie Toolbox allows you to store information about the sound data in the sound description.
Sample size indicates the number of bits used to encode the amplitude value for each sample.
The size of a sample determines the quality of the sound, since more bits can represent more amplitude values. Sample rate indicates the number of samples captured per second. The sample rate also influences the sound quality, because higher rates can more accurately capture the original sound waveform. The basic Macintosh hardware supports an output sampling rate of 22.254 kHz. This allows compression of the sound data at ratios of 3 to 1 or 6 to 1.