JEITA CP-3451
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5.4.3 Channels
The number of channels is either monaural or stereo (2 ch).
5.4.4 Compression Schemes
The following three compressions schemes are specified here:
· Uncompressed audio data: PCM ,
· Uncompressed audio data: m-Law PCM (conforming to ITU-T G.711),
· Compressed data: IMA-ADPCM.
5.5 Basic Structure of Audio Data
Exif audio files are based on the RIFF WAVE Form Audio File format adopted as a Windows standard audio file
format, with the addition of various DSC attribute information as needed. Exif audio files are data-compatible with
WAVE Form Audio files and can be played on accessories supplied with Windows.
Of the general attribute information required by DSC applications, the common attributes are recorded on an INFO
list, and the Exif-specific attributes are recorded in Exif chunks. The Exif chunks are provided to enable the addition
of information as necessary, taking advantage of chunk extensibility. The method of recording data in the
Exif-specific chunks is patterned after that for the INFO list.
5.5.1 Basic Structure of WAVE Form Audio Files
The WAVE Form Audio File format is based on the RIFF (Resource Interoperability File Format) tagged file
structure.
A RIFF file consists of basic data blocks called chunks.
(1) Chunk
Using C language syntax, a chunk may be defined as a structure, like that in Equation 1. The chunk structure may
also be expressed in graphical form as in .
typedef struct {
unsigned long ckID;
// 4-character code
unsigned long ckSize;
// Size of member <ckData>
unsigned char ckData[ckSize];
// The data in the chunk
} CK; - - - [Equation 1]
Address Offset
Meaning
(Hex)
+00
ckID (4 Bytes)
+04
ckSize (4 Bytes)
+08
ckData[ckSize]
Figure 33 Chunk Structure