mpv does not recognise the MIME type audio/L16

[ewtoombs]

mpv version and platform

1:0.18.1-1, archlinux

Reproduction steps

This can be tested pretty easily using pulseaudio.

$ pacmd load-module module-http-protocol-tcp
$ mpv http://localhost:4714/listen/source/$YOURSOUNDCARDHERE.monitor

Expected behavior

It plays 16-bit signed big endian stereo audio at 44.1kHz as per https://tools.ietf.org/html/rfc2586

Actual behavior

mpv http://localhost:4714/listen/source/alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
Playing: http://localhost:4714/listen/source/alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
[ytdl_hook] youtube-dl failed, trying to play URL directly ... 
Failed to recognize file format.


Exiting... (Errors when loading file)

Log files

http://ix.io/18jr

[wiiaboo]

So basically this needs #3375 applied and then it still needs --demuxer-rawaudio-format=s16be to work.

[ewtoombs]

@wiiaboo currently, yes, but ideally, specifying the audio format is unnecessary for http streams with mime type audio/L16.

[wiiaboo]

Depends. Does ffmpeg recognize it? If not, it's not up to mpv.

[ewtoombs]

It can't be recognised. It's raw audio data without a container. But the MIME type implies s16be, 44.1kHz, stereo.

[ewtoombs]

Unless ffmpeg handles the HTTP, I think it is up to mpv to react to the MIME.

[wiiaboo]

There's no dedicated demuxer in mpv for http. If FFmpeg can't read it, mpv won't either.

[ewtoombs]

But still, does ffmpeg handle the http or does mpv? If it's mpv, then mpv is the only one that can set the demuxer properties properly. L16 has no container. It's impossible for ffmpeg to determine what kind of media it is unless it gets the MIME type from the http stream somehow.

[ewtoombs]

http streams with MIME type audio/L16 can still use the same demuxer everything else uses, but it would just need to automatically add the --demuxer-rawaudio-format=s16be option.

The cleanest would be adding a ffmpeg pseudo-demuxer for this, which sets the right parameters. There's also some mime type matching in demux_lavc.c, but it would be better to hook it up to libavformat's (which was added after mpv started using mime types for probing).

Also let me express my disgust about this RFC.