[FFmpeg-user] yuv420p format

[Ran Shalit]

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:
https://drive.google.com/folderview?id=0B22GsWueReZTTmItd1NFWjFBV2M&usp=sharing
1. They were created by compiling the v4l2 API example from:
http://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html
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
code)
            ./v4l2_example  -f -o -c 10  >
v4l2_default_force_640_480_interleaved_yuyv.yuv

   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  >
v4l2_default_force_640_480_progressive_yuv420.yuv


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

ffplay -f rawvideo -pixel_format yuv420p -video_size 640x480 -i
v4l2_default_force_640_480_progressive_yuv420.yuv

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

Any hint is most appreciated,

Best Regards,
Ran