JEITA CP-3451
- 82 -
In the case of PCM format audio data, the data format of each sample is 8-bit or 16-bit integer. These sample data
formats and their values are given in Table 25.
Table 25 Sample Data Formats and Values
Sample Size
Data Format
Minimum
Interoperability
Maximum
8-bit PCM
Unsigned
Integer
0 (00.H)
128 (80.H)
255 (FF.H)
16-bit PCM
Signed Integer
-32768 (8000.H)
0 (0000.H)
32767 (7FFF.H)
The PCM format audio data contained in data-ck is packed as shown in Figure 40. Here the left-hand byte stores
the lower address and the right-hand byte holds the upper address.
8-bit monaural PCM
Sample 0
Sample 1
Sample 2
Sample 3
Channel 0
Channel 0
Channel 0
Channel 0
Byte 0
Byte 1
Byte 2
Byte 3
8-bit stereo PCM
Sample 0
Sample 1
Channel 0
(left)
Channel 1
(right)
Channel 0
(left)
Channel 1
(right)
Byte 0
Byte 1
Byte 2
Byte 3
16-bit monaural PCM
Sample 0
Sample 1
Channel 0
Lower Byte
Channel 0
Upper Byte
Channel 0
Lower Byte
Channel 0
Upper Byte
Byte 0
Byte 1
Byte 2
Byte 3
16-bit stereo PCM
Sample 0
Channel 0
(left)
Lower Byte
Channel 0
(left)
Upper Byte
Channel 1
(right)
Lower Byte
Channel 1
(right)
Upper Byte
Byte 0
Byte 1
Byte 2
Byte 3
Figure 40 Packing of PCM Audio Data
5.5.3 Basic Structure of m-Law Audio Data
Each of the audio data samples of m-Law audio data has nonlinear (logarithmic) quantization characteristics. For
this reason 16 bits of data may be represented in an 8-bit size. In playback, either the data is first converted to
linear 16-bit data and then put through a linear D/A converter, or else the analog signal is derived by going through
an 8-bit nonlinear D/A converter with characteristics opposite the m-Law quantization characteristics. Details of the
nonlinear quantization characteristics and of the conversion between 8-bit m-Law data and 16-bit linear data are
given in the ITU-T G.711
standard.
When the format type is m-Law (ITU-T G.711) format, the basic structure is expressed as in Figure 41.
The two differences from PCM format are the larger size of fmt-ck (the cbSize file exists) and the existence of
fact-ck.