[FFmpeg-devel] DCT coeffs storing order

Michael Niedermayer michaelni at gmx.at
Mon Nov 7 16:39:12 CET 2011

On Mon, Nov 07, 2011 at 11:36:36AM -0200, Germán Milano wrote:
> Hi,
> Thanks again.
> I think my questions are oriented to FFmpeg implementation mostly. In the
> question
> > When DCT coefficients are stored in the h->mb, in which order are they
> > stored? I mean, do the first 256 correspond to luma, then the following
> > correspond to one of the chromas, and the final 256 correspond to the
> > second chroma component?. In case they're stored like i mentioned, which
> is
> > the order they appear in the array within each component?, e.g., the 256
> > luma coeffs are stored in 'raster scan order'?
> i was just asking how FFmpeg deals with the storing of the coeffs. It's
> really important that i get this right, because i want to do a
> requantification (for transRATING purpouses).

i dont think requantizing the coefficients will work well with intra
prediction. But the layout is quite simple, you can just read it off
the code. luma is at 0, chroma plane 1 is at 256 and chroma plane 2
at 512
each is stored in double zig zag order for 16 blocks and zigzag
order for 4. The block coeffs are in raster scan order.


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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