VS1103B Datasheet, PDF (40/61 Pages) List of Unclassifed Manufacturers – MIDI/ADPCM AUDIO CODEC

VLSI
Solution ^y
VS1103b
VS1103B
7. OPERATION
7.4.4 Playing ADPCM Data
In order to play back your IMA ADPCM recordings, you have to have a file with a header as described
in Chapter 7.4.3. If this is the case, all you need to do is to provide the ADPCM file to VS1103 as an
ADPCM stream.
7.4.5 Sample Rate Considerations
VS10xx chips that support IMA ADPCM playback are capable of playing back ADPCM files with
any sample rate. However, some other programs may expect IMA ADPCM files to have some exact
sample rates, like 8000 or 11025 Hz. Also, some programs or systems do not support sample rates below
8000 Hz.
If SM RECORD PATH is set, recording is performed from the mixer output at exactly 44.1 kHz from
the
mixer
output.
If
SM
RECORD
PATH
is
not
set,
recording
is
performed
at
8kH z
×
XT ALI
12.288M Hz
from
the microphone or line input. From the formula it can be seen that the nominal 8 kHz sample rate can
only be obtained if XTALI = 12.288 MHz. Example: If you have a 12 MHz clock, you will get a sample
rate of 7812.5 Hz, which should be recorded to the file.
7.4.6 Example Code
The following code initializes IMA ADPCM encoding on VS1103 and shows how to read the data.
const unsigned char header[] = {
0x52, 0x49, 0x46, 0x46, 0x1c, 0x10, 0x00, 0x00,
0x57, 0x41, 0x56, 0x45, 0x66, 0x6d, 0x74, 0x20, /*|RIFF....WAVEfmt |*/
0x14, 0x00, 0x00, 0x00, 0x11, 0x00, 0x01, 0x00,
0x40, 0x1f, 0x00, 0x00, 0x75, 0x12, 0x00, 0x00, /*|........@......|*/
0x00, 0x01, 0x04, 0x00, 0x02, 0x00, 0xf9, 0x01,
0x66, 0x61, 0x63, 0x74, 0x04, 0x00, 0x00, 0x00, /*|.......fact....|*/
0x5c, 0x1f, 0x00, 0x00, 0x64, 0x61, 0x74, 0x61,
0xe8, 0x0f, 0x00, 0x00
};
unsigned char db[512]; /* data buffer for saving to disk _*/
Version 1.01, 2007-09-03
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