[Bug 1921452] Re: [SRU] alsa-lib: conf: USB - add "Cmedia Audio" to USB-Audio.pcm.iec958_device
1921452 at bugs.launchpad.net
Thu Apr 1 08:37:59 UTC 2021
** Changed in: alsa-lib (Ubuntu Hirsute)
Status: In Progress => Fix Committed
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[SRU] alsa-lib: conf: USB - add "Cmedia Audio" to USB-
Status in OEM Priority Project:
Status in alsa-lib package in Ubuntu:
Status in alsa-lib source package in Focal:
Status in alsa-lib source package in Groovy:
Status in alsa-lib source package in Hirsute:
On Cmedia Audio, unusable SPDIF can be selected as output from PulseAudio.
Disable IEC958 (SPDIF) through ALSA UCM.
With the UCM applied, `pactl` and audio panel in gnome-control-center no longer have SPDIF option.
[Where problems will occur]
"Cmedia Audio" is the sound card name of this usb audio dongle, and this string is got from usb string descriptor, that is to say the "Cmedia Audio" is hard-coded in the firmware of that usb dongle.
Not all Cmedia usb audio dongle use "Cmedia Audio", most of the dongles don't set string descriptor, then the audio driver sets a generic name "USB Audio Device" for them, if a dongle has string descriptor, it may have different string like "C-Media USB Headphone Set", and all dongles I met before don't have SPDIF interface.
So If this SRU could introduce regression, it will happen on a Cmedia usb audio dongle which also hard-codes the "Cmedia Audio" in the string descriptor and it has SPDIF interface on it, after this SRU, users couldn't find the SPDIF playback device from the gnome-sound-setting. But this regression chance is very low since it is very rare a cmedia usb audio dongle uses "Cmedia Audio" in the string descriptor and it is very rare a usb audio dongle has SPDIF interface. So far we haven't met such a cmedia usb audio dongle.
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