Inside Macintosh: Sound /

Chapter 2 - Sound Manager / Sound Manager Reference

Data Structures

Sound Data Chunks

AIFF and AIFF-C files generally contain a Sound Data Chunk that contains the actual sampled-sound data. The SoundDataChunk data type defines a Sound Data Chunk.

TYPE SoundDataChunk =
RECORD
   ckID:       ID;         {'SSND'}
   ckSize:     LongInt;    {size of chunk data}
   offset:     LongInt;    {offset to sound data}
   blockSize:  LongInt;    {size of alignment blocks}
END;

Field Description

ckID

The ID of this chunk. For a Sound Data Chunk, this ID is 'SSND'.

ckSize

The size of the data portion of this chunk. This size does not include the 8 bytes occupied by the values in the ckID and the ckSize fields.

offset

An offset (in bytes) to the beginning of the first sample frame in the chunk data. Most applications do not need to use the offset field and should set it to 0.

blockSize

The size (in bytes) of the blocks to which the sound data is aligned. This field is used in conjunction with the offset field for aligning sound data to blocks. As with the offset field, most applications do not need to use the blockSize field and should set it to 0.

The sampled-sound data follows the blockSize field. If the data following the blockSize field contains an odd number of bytes, a pad byte with a value of 0 is added at the end to preserve an even length for this chunk. If there is a pad byte, it is not included in the ckSize field. For information on the format of the sampled-sound data, see "Sound Files" on page 2-81.