[FFmpeg-devel] Accessing compressed domain data

[Michael Niedermayer]

On Thu, Oct 22, 2009 at 04:58:58PM -0400, guido manfredi wrote:
> Hi,
> 
> I'm running a research project using H.264 video codec.
> I would like to use ffmpeg in order to retrieve frames ( I-frames especially
> ) in compressed domain.
> My goal is to get the DCT coefficients of each I-frame, with only partial
> decoding of the frame.
> 
> Is there a way to stop frame decoding before IDCT, so i can retrieve DCT
> coefficients and btw save computation time ?
> 
> I suppose i should change some lines in h264.c : hl_decode_mb_internal(), is
> that right ?

the clean way to do this is with

if(s->avctx->debug&FF_DEBUG_DCT_COEFF){
    copy coeffs -> picture.dct_coeff[]
}

such a patch might be accepted if it causes no meassureable slowdown!


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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