[Libav-user] H264, DCT and MV data

András Bohó andras.boho at gmail.com
Thu Apr 14 12:40:06 CEST 2011

Dear All,

For cryptography purposes, I would like to insert decryption in the h264
codec file.
What I am looking for is actually the points where I can access the each DCT
coeff and MV value in CAVLC mode.

What I know so far is that there is a very long function called
decode_mb_cavlc() and it has lines "tprintf(s->avctx, "final mv:%d %d\n",
mx, my);" after which the final mv is calculated but can anybody tell me
where I can access the residual values that are stored in the video file. So
at which point is that read?

As for dct level and sign values, I have the same question. Where can I
access the values directly after they get read from the source file? (so
that I can manipulate/decrypt them)

Thanks for help.
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