[FFmpeg-devel] P/B - frames coeffs

Michael Niedermayer michaelni at gmx.at
Sat Nov 19 20:52:20 CET 2011

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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