ALSA: support selection of ALSA mixer - for (hardware-based) volume control about librespot HOT 4 CLOSED

Comment by plietar
Thursday Jan 05, 2017 at 13:31 GMT

This is definitely a frequent request (#128 and #75).
Originally, librespot only supported PortAudio, which doesn't have any sort of volume control.

@joerg-krause had an implementation for ALSA at some point. It would need to be adjusted to at least fallback to software volume control for other backends

from librespot.

Comment by arigit
Sunday Mar 26, 2017 at 18:04 GMT

Noticed that today's binary release for raspberry by @herrernst supports a "--mixer" option!
Tried it & librespot crashed like so:

/home/osmc/librespot# /home/osmc/librespot/librespot --name Raspberry --cache /tmp --bitrate 320 --backend alsa --device hw:0 --mixer Digital
INFO:librespot: librespot 6f1b785 (2017-03-26). Built on 2017-03-26.
thread 'main' panicked at 'Invalid mixer', /buildslave/rust-buildbot/slave/stable-dist-rustc-cross-host-linux/build/src/libcore/option.rs:715
note: Run with RUST_BACKTRACE=1 for a backtrace.

Amixer shows that the "Digital" mixer exists:

...
Simple mixer control 'Digital',0
Capabilities: pvolume pswitch
Playback channels: Front Left - Front Right
Limits: Playback 0 - 207
Mono:
Front Left: Playback 207 [100%] [0.00dB] [on]
Front Right: Playback 207 [100%] [0.00dB] [on]
...

Tried with other mixers shown by alsamixer & amixer, and they all crash librespot

Wondering if the --mixer command line switch is not yet ready for use, or if it's meant to be used differently

from librespot.

Comment by joerg-krause
Monday Mar 27, 2017 at 05:39 GMT

It's meant to use different. For now, there is only one mixer supported: softmixer. --mixer is not the ALSA mixer device name.

from librespot.

This is @joerg-krause's implementation that @plietar referenced. @joerg-krause Did you make any more progress with this?

And as an addition note I'm going to close this issue and refer people to #45 for continued discussion as it looks more informative.

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