[Libav-user] Scale image from 4:2:2 to 4:2:0

[David Sze]

On Fri, Mar 30, 2012 at 4:57 AM, Ушаков Андрей <sorcchan at gmail.com> wrote:

> 30 марта 2012 г. 2:01 пользователь David Sze <sze.david at gmail.com>написал:
>
>>
>> The comments in your source file say:
>>
>>
>>  * Watch original video:
>>  * vlc video422.raw :demux=rawvid --rawvid-fps=25 --rawvid-width=720
>> --rawvid-height=576 --rawvid-chroma=UYVY
>>  * Watch "scaled" result:
>>  * vlc video420p.raw :demux=rawvid --rawvid-fps=25 --rawvid-width=720
>> --rawvid-height=576 --rawvid-chroma=YV12
>>
>>
>> So you probably should be using PIX_FMT_UYVY422 instead of
>> PIX_FMT_YUYV422 when doing the conversion.
>>
>
> Thanks a lot, David! :) Now all works perfectly. I just thought YUYV and
> UYVY is the same.
>
> One more question: what PixelFormat is YV12? As I see its not
> PIX_FMT_YUV420P.
>

They're similar, but the U and V planes are swapped.

http://wiki.videolan.org/YUV#YUV_4:2:0_.28I420.2FJ420.2FYV12.29
http://en.wikipedia.org/wiki/YUV#Y.27UV420p_.28and_Y.27V12_or_YV12.29_to_RGB888_conversion
http://www.fourcc.org/yuv.php#YV12
http://www.fourcc.org/yuv.php#IYUV

Note that YUV420P is a.k.a. I420 and IYUV.

The vlc parameter you pass to watch the scaled frame should be I420 instead
of YV12.
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