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VS1103b Datasheet

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 8kHz ×

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, /*|......ù.fact....|*/

0x5c, 0x1f, 0x00, 0x00, 0x64, 0x61, 0x74, 0x61,

0xe8, 0x0f, 0x00, 0x00

};

unsigned char db[512]; /* data buffer for saving to disk */

Version: 1.04, 2018-03-16

VS1103 Datasheet(PDF) 40 Page - VLSI Solution Oy