Re: [FFmpeg-devel] [FEATURE PROPOSAL] Extracting codec-level data to binary files

[Michael Niedermayer <michael@niedermayer.cc>]

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Hi Ronald

On Thu, May 22, 2025 at 07:59:06AM -0400, Ronald S. Bultje wrote:
> Hi,
> 
> On Wed, May 21, 2025 at 9:34 AM Timothée <
> timothee.informatique@regaud-chapuy.fr> wrote:
> 
> > Hello,
> >
> > I am interested in expanding ffmpeg's capabilities to extract
> > low-level data from video codecs. Specifically, I'd like to implement
> > functionality that would allow exporting frame data, macroblock
> > information, quantization tables, and similar codec-specific elements
> > to binary files for further analysis.
> >
> > After searching through the documentation and existing features, I
> > haven't found similar functionality, though I may have missed
> > something. Has this been implemented before, or are there related
> > features I should examine?
> 
> 
> Some older codecs implement minor variants for this, e.g. grep
> for AV_FRAME_DATA_MOTION_VECTORS, which attaches a frame's motion vectors
> to the picture data. I believe there's an example app and possibly a filter
> to overlay MVs on top of the video frame based on this concept. You could
> extend this to cover other (macro)block info. There used to be a variant of
> this for quant-tables also but I can't find it, maybe it was removed.

For motion vectors:
./ffplay -flags2 +export_mvs -i matrixbench_mpeg2.mpg  -vf codecview=mv=pf+bf+bb

For macroblock segmentation and type vissualization + also motion vectors:
ffplay-3.4.13 -debug vis_mb_type matrixbench_mpeg2.mpg  -vf codecview=mv=pf+bf+bb

For QP vissualization + also motion vectors:
ffplay-3.4.13 -debug vis_qp matrixbench_mpeg2.mpg  -vf codecview=mv=pf+bf+bb

For qp values dumped on the console
./ffplay  -debug qp  -i matrixbench_mpeg2.mpg

[...]
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