[FFmpeg-trac] #4030(avdevice:open): V4L2 recording results in invalid data & buffer still owned errors

[FFmpeg]

#4030: V4L2 recording results in invalid data & buffer still owned errors
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             Reporter:  thender     |                    Owner:  holden
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avdevice
              Version:  git-master  |               Resolution:
             Keywords:  v4l2        |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  1           |
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Comment (by corco):

 I have the exact same issue with a different device, an INOGENI 4K2USB. I
 should probably disclaim that I am one of the hardware designers.

 The issue is the same, after the device is connected, any ffmpeg command
 will work. However, if ffmpeg is stopped and the same command (or another)
 is inputted, it fails with "The v4l2 frame is 0 bytes, but XXXXXXX bytes
 are expected".

 The issue doesn't affect every kernel. I don't have any problem with my
 Centos 3.10.0 kernel, but the problem was reported and confirmed on Ubuntu
 14.04 3.16.0 kernel. So the issue may be with the V4L2 driver, but FFmpeg
 is the only one to complain about it; gstreamer and VLC are fine.

 I tested the 0001-lavd-v4l2-print-buffer-flags-in-case-of-error.patch from
 holden and was pleased to see that it fixed the problem, albeit a rather
 harmless error message at the beginning. Is there any chance to apply the
 patch to upstream?

 If you're interested in investigating the issue, I could provide SSH to
 the ubuntu machine.

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Ticket URL: <https://trac.ffmpeg.org/ticket/4030#comment:22>
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