[Bug 268136] [snd_uaudio] Distorted audio from MOTU M4 USB interface

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 09 Dec 2022 21:02:26 UTC

--- Comment #10 from mburetorp <markus.buretorp@gmail.com> ---
I have tested virtual_oss now but so far I haven't been able to get any sound.
Do you have an argument list that should work in my case? I don't quite
understand how -C -c should be used.

Without virtual_oss I have concluded that hw.usb.uaudio.default_bits=32 is the
only bit depth that works, so dev.pcm.4.play.vchanformat should probably be s32
as well. In bitperfect mode that seem to be the only format that I can use, but
no applications understand 32 bit 4 channels, but maybe virtual_oss can. I just
want stereo sound in channel 1/2 and channel 3/4 to be muted.

root@marcus:~ # sysctl dev.pcm.4.bitperfect
dev.pcm.4.bitperfect: 1
root@marcus:~ # sysctl dev.pcm.4.play.vchanformat
dev.pcm.4.play.vchanformat: s32le:4.0
root@marcus:~ # sysctl dev.pcm.4.play.vchanformat=s16le:2.0
dev.pcm.4.play.vchanformat: s32le:4.0 -> s32le:4.0
root@marcus:~ # sysctl dev.pcm.4.bitperfect=0
dev.pcm.4.bitperfect: 1 -> 0
root@marcus:~ # sysctl dev.pcm.4.play.vchanformat=s16le:2.0
dev.pcm.4.play.vchanformat: s32le:4.0 -> s16le:2.0
root@marcus:~ # sysctl dev.pcm.4.bitperfect=1
dev.pcm.4.bitperfect: 0 -> 1
root@marcus:~ # sysctl dev.pcm.4.play.vchanformat=s16le:4.0
dev.pcm.4.play.vchanformat: s16le:2.0 -> s32le:4.0

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