[FFmpeg-user] FFMpeg: Webcam capture not fast enough. Ffmpeg dies half way (Linux)

Raghu Ram iamanonymouscoward at gmail.com
Wed Aug 21 22:24:06 CEST 2013

Hi All,

I am trying to capture webcam output through FFMpeg (on linux inside a
virtual machine). here is the detailed question.  The capture is not
proceeding beyond 10 seconds. Can you please help.

The command I used is:

$ ffmpeg -y  -f video4linux2 -r 20 -s 160x120 -i /dev/video0 -acodec
libfaac -ab 128k  /tmp/web.avi

The most important message I am getting is:

*[video4linux2,v4l2 @ 0x9e43fa0] The v4l2 frame is 46448 bytes, but 153600
bytes are expected*
Information on the google for this error is scarce. I am going nuts over
this problem. Please help.

Ps: Also asked at

*Complete message from ffmpeg:*

ffmpeg version N-55159-gf118b41 Copyright (c) 2000-2013 the FFmpeg developers
  built on Aug 18 2013 09:09:13 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --enable-libass --prefix=/opt/ffmpeg --enable-debug
  libavutil      52. 40.100 / 52. 40.100
  libavcodec     55. 19.100 / 55. 19.100
  libavformat    55. 12.102 / 55. 12.102
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 82.100 /  3. 82.100
  libswscale      2.  4.100 /  2.  4.100
  libswresample   0. 17.103 /  0. 17.103
[video4linux2,v4l2 @ 0x9e43fa0] The V4L2 driver changed the video from
160x120 to 320x240
[video4linux2,v4l2 @ 0x9e43fa0] The driver changed the time per frame
from 1/20 to 1/15
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 6424.338678, bitrate: 18432 kb/s
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422,
320x240, 18432 kb/s, 15 fps, 15 tbr, 1000k tbn, 1000k tbc
Codec AVOption ab (set bitrate (in bits/s)) specified for output file
#0 (/tmp/web.avi) has not been used for any stream. The most likely
reason is either wrong type (e.g. a video option with no video
streams) or that it is a private option of some encoder which was not
actually used for any stream.
Output #0, avi, to '/tmp/web.avi':
    ISFT            : Lavf55.12.102
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 320x240,
q=2-31, 200 kb/s, 20 tbn, 20 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> mpeg4)
Press [q] to stop, [?] for help
[video4linux2,v4l2 @ 0x9e43fa0] The v4l2 frame is 46448 bytes, but
153600 bytes are expected
/dev/video0: Invalid data found when processing input
frame=   29 fps= 14 q=3.5 Lsize=      87kB time=00:00:01.45 bitrate=
video:80kB audio:0kB subtitle:0 global headers:0kB muxing overhead 7.760075%
[video4linux2,v4l2 @ 0x9e43fa0] Some buffers are still owned by the
caller on close.

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