[FFmpeg-devel] P/B - frames coeffs

Germán Milano g.milano87 at gmail.com
Mon Nov 21 13:18:33 CET 2011


Michael:

Thanks for the info, i'll look for that transform.

Still, i can't find where the P and B coeffs are stored. They appear not to
match with the coeffs i get using VisualMpegPRO.

Where could they be?, i'd really appreciate the help.

Thanks again,
Jeremy

On Sat, Nov 19, 2011 at 5:52 PM, Michael Niedermayer <michaelni at gmx.at>wrote:

> On Sat, Nov 19, 2011 at 12:09:38PM -0200, Germán Milano wrote:
> > Hi everyone!..
> >
> > I am decoding a video stream in h264 using ffmpeg, and printing out the
> DCT
> > coeff after dequantification. To corroborate this I am using
> VisualMpegPRO
> > and checking out wether coefficients per macroblock have the same value
> > (between ffmpeg print outs and VisualMpegPRO) and going over the order in
> > which they are stored.
> >
> > I could check all this for I macroblocks: all coeff are stored in h->mb
> and
> > h->mb_luma_dc.
> > I noticed that DC coefficients are not dequantized. Why does this
> happen???
>
> the dc coeffs of some MB types are passed through another decorrelation
> transform before dequant
>
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> it is not once nor twice but times without number that the same ideas make
> their appearance in the world. -- Aristotle
>
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