[FFmpeg-user] yuv420p format

Ran Shalit ranshalit at gmail.com
Fri Jan 8 13:23:39 CET 2016

On Fri, Jan 8, 2016 at 11:02 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> Ran Shalit <ranshalit <at> gmail.com> writes:
>> I have captured video with V4L2_PIX_FMT_YUV420 format
> How did you capture the video?
>> But the captured video is not played correctly with
> What does "not correctly" mean?
> Please provide a sample.
>> ffplay -f rawvideo -pixel_format yuv420p
>> -video_size 1920x1080 -i cap_yuv420p.yuv
>> Is V4L2_PIX_FMT_YUV420 (v4l2)  and yuv420p (ffmpeg) the same ?
> Yes, see:
> http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavdevice/v4l2-common.c
> Carl Eugen
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Hi Carl,

Thank you very much for your reply.

The sample are here:
1. They were created by compiling the v4l2 API example from:
2. modprobe vivi (kernel must contain module vivi)
3. runnning the compiled executable:
    3.1 the example as-is (no changes)
            ./v4l2_example  -o -c 10  > v4l2_default.yuv

    3.2 the example as-is (no changes)  but unning with (-f) - force
parameter to 640x480 interleaved, yuyv (can be seen in the example
            ./v4l2_example  -f -o -c 10  >

   3.3 the example with minor modification so that the force section
in code will use   V4L2_PIX_FMT_YUV422P format, and progressive
(V4L2_FIELD_NONE               instead of V4L2_FIELD_INTERLEAVED), the
resolution is the same (640x480).
            ./v4l2_example  -f -o -c 10  >

Trying to run the yuv420 sample (and the other two) always gives bad images:

ffplay -f rawvideo -pixel_format yuv420p -video_size 640x480 -i

I've tried many change in ffplay parameters, but can't understand
what's the problem.

Any hint is most appreciated,

Best Regards,

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