gstreamer 1.20: v4l2bufferpool spams "newly allocated buffer is not free"

[Michiel Konstapel]

Hi Nicolas,

On 24-06-2022 19:50, Nicolas Dufresne via gstreamer-devel wrote:
> Hi,
>
>
>     gstv4l2bufferpool.c:478:gst_v4l2_buffer_pool_alloc_buffer:<v4l2src0:pool0:src>
>
>     newly allocated buffer 1 is not free
>
>     Despite the warnings, the pipeline appears to work, but I would
>     prefer
>     it to not spam warnings continuously :) Any ideas? This is on Ubuntu
>     20.04, on different PCs and with different cameras.
>
>
> Do you have any information about the driver?

It's a very common Logitech C920 webcam (but I've seen the same message 
with a Z-Cam M3 camera). I think that uses a generic UVC driver? 
Anything I can run to get you more info?

Something interesting perhaps:

v4l2-ctl -d /dev/video2 --list-formats
ioctl: VIDIOC_ENUM_FMT
     Index       : 0
     Type        : Video Capture
     Pixel Format: 'YUYV'
     Name        : YUYV 4:2:2

     Index       : 1
     Type        : Video Capture
     Pixel Format: 'MJPG' (compressed)
     Name        : Motion-JPEG

If I use the YUYV mode, I *don't* get the warning:

GST_DEBUG=3 gst-launch-1.0 v4l2src device=/dev/video2 ! video/x-raw ! 
videoconvert ! autovideosink

reports no warnings (but the framerate is awful, of course).

HTH,
Michiel
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