terrible audio on webcam

[Shlomo Solomon]

Let me start by saying that for years I've tried to get a "cheap"
webcam to work on Linux with very little success, but UVC seems to have
changed that. I bought a cheap camera on Aliexpress and it works
perfectly - REAL plug-and-play.

BUT that's only true of the video. The audio is unbelievably bad - all
I get is a weird squeaky noise. It seems to be picking up just a few
random frames and skipping most of the sound.

2 comments:
1 - it's not the hardware because it works fine on a Windows laptop
2 - I do have a work-around - I use the camera for video and a
"regular" microphone connected to the sound card.

But it would be nice to figure out what's wrong and how to fix the
camera's audio.

I've tested - and seen (actually heard) the same problem using
zoom, cheese, webcamoid, arecord + aplay, audacity.


I do see a problem in dmesg, but have no idea what to do about it.
Here's the output:


[1371995.047030] usb 1-5: new high-speed USB device number 96 using
xhci_hcd  
[1371995.196029] usb 1-5: New USB device found, idVendor=1224,
idProduct=2a25, bcdDevice= 1.00  
[1371995.196035] usb 1-5: New USB device strings: Mfr=1, Product=2,
SerialNumber=0 
[1371995.196038] usb 1-5: Product: USB PHY 2.0 
[1371995.196041] usb 1-5: Manufacturer: Jieli Technology
[1371995.197540] uvcvideo: Found UVC 1.00 device USB PHY 2.0 (1224:2a25)
[1371995.199845] input: USB PHY 2.0: USB CAMERA as
/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5:1.0/input/input95
[1371995.205917] usb 1-5: failed to read current rate; disabling the
check
[1371995.208350] usb 1-5: Warning! Unlikely big volume range (=4096),
cval->res is probably wrong.
[1371995.208351] usb 1-5: [3] FU [Mic Capture Volume] ch = 1, val =
0/4096/1 
[1371995.394425] xhci_hcd 0000:00:14.0: WARN: buffer overrun event for
slot 55 ep 4 on endpoint
[1371995.394428] retire_capture_urb: 1714 callbacks suppressed 
[1371995.395424] xhci_hcd 0000:00:14.0: WARN: buffer overrun event for
slot 55 ep 4 on endpoint 
[1371995.398423] xhci_hcd 0000:00:14.0: WARN: buffer overrun event for
slot 55 ep 4 on endpoint

and the "buffer overrun event"  is then reported 1700 !!! times after
that


I've seen many references to retire_capture_urb: XXX callbacks
suppressed - for example:
https://www.spinics.net/lists/alsa-devel/msg119934.html 
But I have no idea how to fix this.





-- 
Shlomo Solomon
http://the-solomons.net
Claws Mail 3.17.5 - KDE Plasma 5.18.5 - Kubuntu 20.04