Hi all! On 2019-03-20 19:56 +0100, Alexander Strasser wrote: > I had found that when capturing video for some hours from > USB Camera-B4.09.24.1 (Manufacturer: OmniVision Technologies, Inc.), > sometimes when invoking the ioctl DQBUF, the returned buffer is not > filled with the size we expect for the raw video frame. > > Here are two examples for such occurrences: > > [video4linux2,v4l2 @ 0x258b440] Dequeued v4l2 buffer contains 609596 > bytes, but 614400 were expected. Flags: 0x00000001. > /dev/video1: Invalid data found when processing input > > [video4linux2,v4l2 @ 0x225f440] Dequeued v4l2 buffer contains 609508 > bytes, but 614400 were expected. Flags: 0x00000001. > /dev/video1: Invalid data found when processing input > > The ffmpeg CLI tool will then stop capturing and exit. > > To avoid this, return FFERROR_REDO instead. I have not seen the > issue appearing twice or more often in a row. It was more like > one single error every two hours.
After thinking about the FFERROR_REDO approach some more, I think it is not ideal in the case where a driver permanently delivers frames of unexpected size. The FFmpeg lib call would not return to the client, potentially freezing the running program. So maybe the zero-sized package approach, like we do with the corrupted frames, is more robust here? Any opinions? Best regards, Alexander > > While searching for the above quoted error message I found a ticket > that mentions this type of problem on our tracker. > > Fixes #4795 > --- > libavdevice/v4l2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c > index 1b9c6e7..5a1b324 100644 > --- a/libavdevice/v4l2.c > +++ b/libavdevice/v4l2.c > @@ -542,7 +542,7 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket > *pkt) > "Dequeued v4l2 buffer contains %d bytes, but %d were > expected. Flags: 0x%08X.\n", > buf.bytesused, s->frame_size, buf.flags); > enqueue_buffer(s, &buf); > - return AVERROR_INVALIDDATA; > + return FFERROR_REDO; > } > } > > -- _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
