Hi all!

I am not entirely sure if this is the right place to address my issue,
so apologies in advance if I am - but I was encouraged to bring this
matter up here by someone who clearly knows way more about Linux than I do.

I got a Rodecaster Pro USB device that has been causing trouble before
and already lead to quirk handling in the kernel for the sample rate,
see
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/usb/format.c?h=v5.8#n412

The Rodecaster is running fine on my laptop, but on my desktop, only
audio input is working. The audio output is distorted. It's played kind
of very slowly. Interestingly, if the source is a video file, the video
plays slower, e.g. YouTube in a browser. I have never seen anything like
that before.

I have tried to figure out what the cause might be and I think I have
reached the end of where I can get to on my own. I have documented most
things at https://ubuntuforums.org/showthread.php?t=2461568

Putting my last step it in a nutshell: I have booted both my computers
with a plain Ubuntu 21.04 from a pen drive (it uses kernel version
5.11.0-16-generic) to make sure it's not some different configuration
that I have set up over the years on my systems (both Ubuntu 20.04 with
kernel 5.8.18). I attached the Rodecaster. It runs fine on my laptop,
but not on my desktop (used the output test from).

I then detected the card number with

aplay -l

I killed pulseaudio with

pulseaudio -k

I then played the same sample (encoded in 48000 Hz in PCM signed 32 bit
little endian format) using

aplay -f S32_LE -c 2 -r 48000 -D hw:x ~/sample.wav

where x is the appropriate card number and the rest of the arguments
meet the Rodecaster's narrow specification. It's playing fine on the
laptop, but distorted on the desktop. As far as I understand using aplay
this way without a plugin should send the file directly to the device,
so I assume there's something on the way from aplay to the Rodecaster
that's interfering (kernel or even some piece of hardware) - and that
definitely is where my expertise ends (rather a little before :-)).

I'll gladly contribute any information that could be useful and I will
willingly help to debug this problem if it may be related to the kernel.
If there's anything I can do, please let me know.

Cheers,
Oliver


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