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  1. Hi

    considering my source

    I use ffmpeg to:

    ffmpeg -i c0020.mxf -vcodec mjpeg -pix_fmt yuv422p -q:v 0 -an output.avi

    convert .mxf in mjpeg

    But when I try to open it in virtualdub I get this error:

    [Attachment 24636 - Click to enlarge]

    multiple chroma blocks not supported.

    Can I enhance the encoding in FFMPEG so virtualdub can open output.avi correctly, of course keeping the mjpeg encoding ?


    ps. to decompress, in virtualdub, I use the internal decompressor (option, pref., avi-->prefer internal decoders)
    please I like to use internal mjpeg decompressor, not other decompressor
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  2. I used your command line on the same source file. VirtualDub had no problem opening the AVI. ffmpeg was used to decode it.

    Click image for larger version

Name:	C0020.jpg
Views:	474
Size:	47.5 KB
ID:	24763

    I suspect VirtualDub's internal MJPEG decoder doesn't support YUV 4:2:2.
    Last edited by jagabo; 24th Apr 2014 at 11:03.
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  3. Why do you want to use internal mjpeg decoder ?
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  4. Originally Posted by jagabo View Post

    I suspect VirtualDub's internal MJPEG decoder doesn't support YUV 4:2:2.
    Seems to decode ok with other MJPEG encoders, eg.. picvideo at 4:2:2

    marcorocchini - this doesn't affect results of vdub's internal decoder, but you can increase ffmpeg's mjpeg encoding quality by locking the min/max quantizers . If you don't specify min/max, the quantizer will still be variable

    -q:v 1 -qmin 1 -qmax 1
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  5. mmmmmmmmmmmmmmmmmmmmmmmmmmmm interesting. Absolute interesting.

    the -q:v 1 -qmin 1 -qmax 1 to increase quality.

    However it's strange that virtualdub can not decode with internal mjpeg decoder, wich means "multiple chroma blocks not supported" ?

    In effects does not seems a problem of 422, because ohters encoding (eg picvideo) in 422 are well opened by virtualdub. This problem is specific of the ffmpeg mjpeg. I have try to encode in mjpeg with virtualdub using the FFdshow mjpg and the risults is the same of the ffmpeg encoding ... what a terrible thing
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