JEITA CP-3451
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5.6 Chunks Used
The chunks used in Exif audio files are described here.
5.6.1 WAVE Form Audio File Basic Chunks
The basic chunks of a WAVE Form Audio File, as is evident from the basic structure of the WAVE file shown in
Figure 35, are the four below.
· RIFF chunk
· fmt chunk
· fact chunk
· data chunk
[Additional Explanation]
The fmt chunk, fact chunk and data chunk are sub-chunks of the RIFF chunk. A WAVE file consists of one RIFF
chunk, with specific information recorded in the sub-chunks.
Only when the form type is PCM (Pulse Code Modulation) format, the fact chunk is unnecessary. With non-PCM
formats such as m-Law and IMA-ADPCM, it is mandatory, which is why fact-ck is included in the basic chunks here.
It is possible to add other optional sub-chunks as well.
At the head of the chunk data (ckData) of the RIFF chunk there is a form type called "WAVE".
5.6.2 LIST Chunk and INFO List
A WAVE form and other RIFF forms store a variety of information in sub-chunks of the RIFF chunk. These
sub-chunks in many cases are specific to each form type; but there are also general-purpose chunks for storing
additional information regardless of the data specified for a given form type.
One of these general-purpose chunks is the LIST chunk. Here the use of the LIST chunk is explained.
(1) LIST Chunk
The LIST chunk is a general-purpose chunk that may be used with the files of many different form types. The LIST
chunk is a pre-registered general-purpose chunk, so its ckID (chunk ID) is written in upper-case letters.
Included in the LIST chunk is a sub-chunk list (series of sub-chunks) and sequence designation.
The LIST chunk ckData (chunk data) consists of a four-character code at the beginning called a listType (list type),
followed by the sub-chunk list.
This structure resembles that of the RIFF chunk, but the LIST chunk is always farther down the hierarchy than the
RIFF chunk.
The list type is used to identify the list contents. For this reason there are list types that are used only with certain
form types. If a list type is encountered that cannot be Interoperability, that LIST chunk may be ignored.
The list type shall be registered. A general-purpose list type that is registered and may be used with various form
types is written in all upper-case letters.
A list type that can be used only with a specific form type is written in lower-case letters.