[FFmpeg-devel] YUV video to RGB image export color conversion issue

[Peter B.]

Hi,

I've found a bug in color conversion from YUV422p to RGB and posted
details about it to ffmpeg-devel on March 1st.

Baptiste Coudurier wrote a patch, attached it and I've verified that it
works. :)

Now I've seen that this fix has not been applied to trunk, so I thought
I might repost this on ffmpeg-devel.

The video as well as the exported images with and without the error can
be seen at:
http://download.das-werkstatt.com/pb/mthk/examples/color_problem/problem.html

I've added it to ffmpeg bugtracking in Trac as issue #143:
http://ffmpeg.org/trac/ffmpeg/ticket/143

I'm also attaching the Baptiste's patch.


Thanks,
Pb


// ------------ My message from 01.March.2011 -------------------------
Hello,

I'm currently developing a test-video (for automatically finding
field/frame drops in A/D converters), and I've run into a
color-conversion issue with ffmpeg:

When extracting images from the video (yuv422p), the color values in
the interlaced areas of the video are deviate from their original
beyond recognition.

I've uploaded the source video [1] and the resulting images on my
webserver, so you can more easily see what I mean:
http://download.das-werkstatt.com/pb/mthk/examples/color_problem/problem.html

I've tried to extract the images with 3 different tools:
1) ffmpeg
2) mplayer
3) virtualdub

VirtualDub exports the images as I'd expect it, whereas mplayer and
ffmpeg don't. :(

Here's the ffmpeg call I've used:
"ffmpeg -vframes 4 -i 'testvideo_color_rectangles-YUV422P.avi'
-pix_fmt rgb24 -f image2 '%03d.bmp'"

(It's also strange, that the resulting bitmap isn't RGB24, but BGR24)


What am I doing wrong?

Thank you very much for any hint/help.

Yours,
Pb


== References:
[1]
http://download.das-werkstatt.com/pb/mthk/examples/color_problem/testvideo_color_rectangles-YUV422P.avi


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