VS1103B Datasheet, PDF (39/61 Pages) List of Unclassifed Manufacturers – MIDI/ADPCM AUDIO CODEC

VLSI
Solution ^y
VS1103b
VS1103B
7. OPERATION
7.4.3 Adding a RIFF Header
To make your IMA ADPCM file a RIFF / WAV file, you have to add a header before the actual data.
Note that 2- and 4-byte values are little-endian (lowest byte first) in this format:
File Offset Field Name
Size Bytes
Description
0 ChunkID
4 ChunkSize
8 Format
12 SubChunk1ID
4 "RIFF"
4 F0 F1 F2 F3
4 "WAVE"
4 "fmt "
File size - 8
16 SubChunk1Size
20 AudioFormat
22 NumOfChannels
24 SampleRate
28 ByteRate
4 0x14 0x0 0x0 0x0 20
2 0x11 0x0
0x11 for IMA ADPCM
2 0x1 0x0
Mono sound
4 R0 R1 R2 R3
0x1f40 for 8 kHz
4 B0 B1 B2 B3
0xfd7 for 8 kHz
32 BlockAlign
34 BitsPerSample
36 ByteExtraData
38 ExtraData
40 SubChunk2ID
44 SubChunk2Size
48 NumOfSamples
52 SubChunk3ID
56 SubChunk3Size
2 0x0 0x1
2 0x4 0x0
2 0x2 0x0
2 0xf9 0x1
4 "fact"
4 0x4 0x0 0x0 0x0
4 S0 S1 S2 S3
4 "data"
4 D0 D1 D2 D3
0x100
4-bit ADPCM
2
Samples per block (505)
4
Data size (File Size-60)
60 Block1
256
First ADPCM block
316 . . .
More ADPCM data blocks
If we have n audio blocks, the values in the table are as follows:
F = n × 256 + 52
R = F_s (see Chapter 7.4.1 to see how to calculate F_s)
B
=
Fs×256
505
S = n × 505. D = n × 256
If you know beforehand how much you are going to record, you may fill in the complete header before
any actual data. However, if you don’t know how much you are going to record, you have to fill in the
header size datas F , S and D after finishing recording.
The 128 words (256 bytes) of an ADPCM block are read from SCI IN0 and written into file as follows.
The high 8 bits of SCI IN0 should be written as the first byte to a file, then the low 8 bits. Note that this
is contrary to the default operation of some 16-bit microcontrollers, and you may have to take extra care
to do this right.
A way to see if you have written the file in the right way is to check bytes 2 and 3 (the first byte counts as
byte 0) of each 256-byte block. Byte 2 should always be less than 90, and byte 3 should always be zero.
Version 1.01, 2007-09-03
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