I have tested the alsamixer with 2 different 8ch usb sound cards (UAC2 compatible) and the assignment of the volume controls to the respective channel is partly wrong on both cards. The volume control for rear changes the volume of the center and subwoofer/LFE and the volume control for "Center" and "Woofer" changes the volume of the rear speakers.
According to the usb audio class 2 specification, chapter "4.1 Audio Channel Cluster Descriptor", the volume controls index must be (for a 8ch sound card):
1 = FL
2 = FR
3 = C
4 = LFE
5 = RL
6 = RR
7 = SL
8 = SR
The current implementation as following assignment:
1 = FL
2 = FR
3 = RL
4 = RR
5 = C
6 = LFE
7 = SL
8 = SR
Unfortunately, I can not judge whether this is a problem in the program or driver (audio usb).
If you have any questions, feel free to contact me.
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ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu71.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: X-Cinnamon
DistroRelease: Ubuntu 21.10
InstallationDate: Installed on 2019-11-02 (905 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
Package: alsa-utils 1.2.4-1ubuntu4
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 5.13.0-37.42-generic 5.13.19
RebootRequiredPkgs: Error: path contained symlinks.
Tags: impish
Uname: Linux 5.13.0-37-generic x86_64
UpgradeStatus: Upgraded to impish on 2021-10-22 (184 days ago)
UserGroups: adm cdrom dialout dip libvirt lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True
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