[libav-bugs] [Bug 221] New: swscale gives incorrect colors with PIX_FMT_YUYV422 and SWS_BILINEAR

bugzilla-daemon at aruru.libav.org bugzilla-daemon at aruru.libav.org
Sun Feb 5 21:50:43 CET 2012


https://bugzilla.libav.org/show_bug.cgi?id=221

           Summary: swscale gives incorrect colors with PIX_FMT_YUYV422
                    and SWS_BILINEAR
           Product: Libav
           Version: git HEAD
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: libswscale
        AssignedTo: bugzilla at libav.org
        ReportedBy: dan at dennedy.org


See also:
https://sourceforge.net/tracker/?func=detail&atid=613414&aid=3483629&group_id=96039

In MLT, I use swsscale to convert some input image formats to yuyv422 with 
SWS_BILINEAR in the flags. Recently, when MLT is built against libav, users
started reporting chroma distortion. In my analysis, swscale is clearing the Cr
components with value 127. With the SWS_BICUBIC flag the problem goes away, and
I have changed my default to mitigate the problem. However, the user may still
select an interpolation method and fall upon this bug. Here are the steps to
reproduce it with avconv and avplay:

avconv -i ~/Videos/A02.mpg -sws_flags bilinear -pix_fmt yuyv422 test.yuv
avplay -framerate 25 -video_size 720x576 -pixel_format yuyv422 test.yuv

Then, you can see the image is overly green and purple.

P.S. Not meant as an insult or anything, but merely as a helpful comparison
point, the bug is not reproducible with ffmpeg libs.

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