Add support pcm_s16le audio

[gtxaspec]

in go2rtc, currently supported is pcm_s16be, can support for pcm_s16le included as well? this would help compatability with certain wyze cameras which use pcm_s16le

[AlexxIT]

Can you provide more info how you pass this data to go2rtc?
I'm not sure that pcm_s16be was right choose. And maybe pcm_s16le more common standard.

[gtxaspec]

we are capturing the audio from alsa which is in pcm_s16le format, then we:

exec:ffmpeg -hide_banner -f alsa -ac 1 -i hw:0,0 -c:a copy -f rtsp {output} to go2rtc`

...obviously s16le doesn't work at the moment but this is how we would do it.

Also, if I remember correctly, LPCM in MOV container is always big-endian? It could be better to support both

[AlexxIT]

Can you enable trace logs for rtsp module? I need to check SDP part from FFmpeg.

[AlexxIT]

FFmpeg + RTSP + pcm_s16le has a problem. FFmpeg doesn't pass info about codec name and params...
I can see you set only one channel for your camera. Please check what the default sample rate:

ffmpeg -hide_banner -f alsa -ac 1 -i hw:0,0 -c:a copy -f null -

[gtxaspec]

@AlexxIT Camera can provide 16000 or 8000 depending on alsa device hw:0,0 or hw:2,0:

[root@WCV3:~]# ffmpeg -hide_banner -f alsa -ac 1 -i hw:0,0 -c:a copy -f null -
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, alsa, from 'hw:0,0':
  Duration: N/A, start: 1689415357.800710, bitrate: 256 kb/s
  Stream #0:0: Audio: pcm_s16le, 16000 Hz, mono, s16, 256 kb/s
[NULL @ 0x775fc040] Requested output format 'null' is not a suitable output format
pipe:: Invalid argument
[root@WCV3:~]# ffmpeg -hide_banner -f alsa -ac 1 -i hw:2,0 -c:a copy -f null -
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, alsa, from 'hw:2,0':
  Duration: N/A, start: 1689415421.555271, bitrate: 128 kb/s
  Stream #0:0: Audio: pcm_s16le, 8000 Hz, mono, s16, 128 kb/s
[NULL @ 0x77dcf040] Requested output format 'null' is not a suitable output format
pipe:: Invalid argument
[root@WCV3:~]# 

[AlexxIT]

OK. Looks like I can detect codec based on bitrate. It always constant for specific sample rate + channels settings.

pcm_s16be, 44100 Hz, stereo => 10
pcm_s16be, 48000 Hz, stereo => 96 L16/48000/2
pcm_s16be, 44100 Hz, mono   => 11

pcm_s16le, 48000 Hz, stereo => 96 (b=AS:1536)
pcm_s16le, 44100 Hz, stereo => 96 (b=AS:1411)
pcm_s16le, 16000 Hz, stereo => 96 (b=AS:512)
pcm_s16le, 8000 Hz, stereo  => 96 (b=AS:256)

pcm_s16le, 48000 Hz, mono   => 96 (b=AS:768)
pcm_s16le, 44100 Hz, mono   => 96 (b=AS:705)
pcm_s16le, 16000 Hz, mono   => 96 (b=AS:256)
pcm_s16le, 8000 Hz, mono    => 96 (b=AS:128)

[AlexxIT]

OK. You can try latest master version. Do you need binary or you can build it yourself?

[gtxaspec]

If you can provide mipsle binary I can test

[AlexxIT]

go2rtc_linux_mipsel.zip

[gtxaspec]

@AlexxIT confirmed working!

[AlexxIT]

https://github.com/AlexxIT/go2rtc/releases/tag/v1.6.1