[FFmpeg-devel] CBP question

Michael Niedermayer michaelni at gmx.at
Tue Nov 1 14:08:44 CET 2011

On Tue, Nov 01, 2011 at 10:11:19AM -0200, Germán Milano wrote:
> Hi everyone,
> I'm trying to print out the DCT coeffs AFTER dequantization. In order to do
> that, i had to take a look at the decode_cabac_residual_internal function
> (in h264_cabac.c). Now, i know that the cbp param represents whether a luma
> block (and corresponding colour diferences blocks) has any DCT coeffs
> distinct from zero. If i understand correctly, that is taken into account
> in that function, in the following line:
> h->cbp_table[h->mb_xy]
> I started with FFmpeg a couple of months ago, so i'm trying to understand
> the terminology in order to fully understand the functions. So, i have the
> following questions:
>    - h -> mb_x and h -> mb_y are the coordinates of the mb in the frame?,
>    is h -> mb_xy the dimension?

mb_xy is the mb index into 2d mb based arrays

>    - The DCTELEMENT passed to the function decode_cabac_residual_internal
>    function is the one that gets 'filled up' with the DCT coeffs after
>    dequant, isn't it?, i.e., h -> mb contains the DCT coeffs after dequant?

yes, thats except for DC

> I hope i'm not bothering anyone with my questions (sorry in advance if i
> am).

no, questions are very welcome. The more people ask, the more they know
and the more they know, the more they can contribute

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20111101/8e4d6c05/attachment.asc>

More information about the ffmpeg-devel mailing list