ALSA volume control is broken [partial fix included]

[benosteen]

benosteen/linux@067ac7c

This doesn't solve the actual problem, but does allow for smooth control of apparent volume using 'alsamixer' for example.

However, this ALSA control doesn't seem to affect the output volume at all, and it's not something I can debug further without knowing more about what values I should be passing over vcos(?) to the OpenMAX IL side of things to affect volume.

[benosteen]

Refined control in this commit: benosteen/linux@25f94a1

I haven't been able to reverse-engineer what the volume curve is for this control, but this commit at least fixes the direction of it, and it now does affect the volume in the way you might expect.

It doesn't quite mute it however...

[popcornmix]

Internally on GPU this is the volume scale:
Sets the volume (attenuation in dB) on the given player as a 24.8 fixed
point number. Negative values (up to -24.0dB) amplify the signal, but
clipping could then occur.

[benosteen]

Brilliant! :) So the upper limit that the volume accepts is at it's loudest -6144 (-24.0). I've guestimated +24.0dB for the quietest value, which seems to be in the right ballpark and altered my fork of the src.

Is there any documentation on how to raise a mute flag on the gpu hw? Does it have that capability?

[popcornmix]

I believe this was fixed in
raspberrypi/linux@b683e89
Please reopen if there is still a problem.