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#295 Wrong MPEG2-image size ?

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nobody
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5
2005-02-25
2005-02-25
No

Hello. :)

I've found a minor issue with MPEG 2 decoding. I don't
*know* whether it can be corrected without interfering
with anything else, but I *think* it is. :)

When decoding MPEG 2 (any DVD, for example), ffdshow
correctly passes the aspect ratio, but doesn't do
necessary cropping.

Because of whatever reason, the DVD material needs to
have 8 leftmost and 8 rightmost pixels cropped away
before resizing to achieve the correct aspect ratio.
libavcodec and libmpeg2 do not do this, which is the
correct behaviour for a general purpose decoder.
However, ffdshow *should* crop those pixels away,
because without it, the image is vertically squished.

Sometimes, this effect is not noticable, but when
watching for example car wheels or something similar,
they are not round, but a bit elliptic. I can provide
screenshots and link to Doom9 forum's dvd-resizing
thread, if needed. :)

Do you think you could modify supplied libavcodec and
libmpeg2 to crop away 8 leftmost and rightmost pixels,
when the format = mpeg2 and the resolution = 720*x ?

Best regards and good night. :)
Mariusz

Discussion

  • Anonymous - 2005-02-25

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    Doing simple cropping shouldn't be too difficult, but after I
    looked at DScaler5 sources it seems to be more complicated
    and will require more work.

     
  • Marius the Mad

    Marius the Mad - 2005-02-25

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    user_id=1221962

    Thank you for looking at it. I'll just wait patiently, then. :)

     
  • Debian

    Debian - 2005-03-30

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    user_id=1249301

    1

     

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