Inside Macintosh: Sound

Form Chunks

All sound files begin with a Form Chunk. This chunk defines the type and size of the file and can be thought of as enclosing the remaining chunks in the sound file. The ContainerChunk data type defines a Form Chunk.



 
TYPE ContainerChunk =

RECORD

    ckID:           ID;             {'FORM'}

    ckSize:         LongInt;        {number of bytes of data}

    formType:       ID;             {type of file}

END;

ckID: The ID of this chunk. For a Form Chunk, this ID is 'FORM' .
ckSize: The size of the data portion of this chunk. Note that the data portion of a Form Chunk is divided into two parts, formType and the remaining chunks of the sound file.
formType: The type of audio file. For AIFF files, formType is 'AIFF' . For AIFF-C files, formType is 'AIFC' .

The size of an entire sound file is ckSize+8 , because the ckSize field incorporates the size of all chunks of the sound file, except the sizes of the ckID and ckSize fields of the Form Chunk itself.