aplay: cannot play S24_LE wav file recorded with arecord

aplay: cannot play S24_LE wav file recorded with arecord

[GitHub issues - opened]

alsa-project/alsa-utils issue #308 was opened from yoshihisa-yamamoto-re:

My environment is alsa-utils version : 1.2.14  (Debian trixie)

I tried to record and play PCM audio as S24_LE format over alsa as follows:
```
arecord  -f S24_LE out.wav
aplay out.wav
```
However, the audio turned into noise and did not seem to play properly.

This problem does **not** seem to occur when using alsa-utils version 1.2.9 (Ubuntu 24.04 LTS).
Searching through the commits, I found the closed issue https://github.com/alsa-project/alsa-utils/pull/260.

>From reading the source, it appears that the header information has been rewritten, so I dumped it to check, and it looks like this:

hexdump of wav created with alsa-utils version 1.2.14 :
```
00000000  52 49 46 46 24 e2 04 00  57 41 56 45 66 6d 74 20  |RIFF$...WAVEfmt |
00000010  10 00 00 00 01 00 01 00  40 1f 00 00 00 7d 00 00  |........@....}..|
00000020  04 00 20 00 64 61 74 61  00 e2 04 00 e6 67 8d ff  |.. .data.....g..|
00000030  c8 fd 8e ff 0c 8e 90 ff  c6 18 92 ff 0a 9e 93 ff  |................|
00000040  ec 1d 95 ff 7e 98 96 ff  d2 0d 98 ff fd 7d 99 ff  |....~........}..|
00000050  10 e9 9a ff 1c 4f 9c ff  35 b0 9d ff 6b 0c 9f ff  |.....O..5...k...|
00000060  cf 63 a0 ff 74 b6 a1 ff  68 04 a3 ff be 4d a4 ff  |.c..t...h....M..|
00000070  86 92 a5 ff cf d2 a6 ff  a9 0e a8 ff 25 46 a9 ff  |............%F..|
```

hexdump of wav created with alsa-utils version 1.2.9 :
```
00000000  52 49 46 46 24 e2 04 00  57 41 56 45 66 6d 74 20  |RIFF$...WAVEfmt |
00000010  10 00 00 00 01 00 01 00  40 1f 00 00 00 7d 00 00  |........@....}..|
00000020  04 00 18 00 64 61 74 61  00 e2 04 00 17 3d fe ff  |....data.....=..|
00000030  3e 3d fe ff 86 41 fe ff  cb 47 fe ff 3b 46 fe ff  |>=...A...G..;F..|
00000040  10 47 fe ff e3 4d fe ff  66 4f fe ff 8d 50 fe ff  |.G...M..fO...P..|
00000050  be 4f fe ff 40 58 fe ff  e7 5b fe ff 27 60 fe ff  |.O..@X...[..'`..|
00000060  f9 60 fe ff ce 61 fe ff  ce 63 fe ff d3 68 fe ff  |.`...a...c...h..|
00000070  83 6f fe ff 84 6c fe ff  22 73 fe ff 91 6d fe ff  |.o...l.."s...m..|
```
As the change in Commit 9cdcbe0e932b97fac88a6195f87647159a6c7194, the header information has changed BitsPerSample (bit_p_spl) from 24bit to 32bit (0x22-0x23).
If I change this header info and treat the 1.2.14 wav as 24-bit per sample as before, the audio seems to play correctly.
I don't have the correct information for S24_LE format, so I don't know if the header information is wrong or if I should modify the arecord to match this 32-bit.

Issue URL     : https://github.com/alsa-project/alsa-utils/issues/308
Repository URL: https://github.com/alsa-project/alsa-utils