[FFmpeg-devel] The quantization parameter QP (s-> qscale) in FFmpeg-"mpeg4videodec.c"-

Moad Toutou moadtoufik at yahoo.fr
Wed Aug 1 16:51:22 CEST 2012

I'm still looking for my quantization parameter QP. I located a set of files that manipulates this variable QP:


The file that interests me most is "mpeg4videodec.c" because I'm more interested in MPEG video decoding.

For me, the value of qp in the file "mpeg4videodec.c" equal to "s-> qscale".

My first question: is "qp" equals "s-> qscale"?

I brought a  modéfications to the file "mpeg4videodec.c" and my second question is:  what is the ffmpeg command for which, the execution of this command, the program will go through by the file instructions "mpeg4 video dec.c"?

This is the kind of instructions that i added in the file "mpeg4videodec.c" :

-av_log(s->avctx, AV_LOG_DEBUG, "the value of qp is %d", s->qscale);
-av_log(s->avctx, AV_LOG_ERROR, "the value of qp is %d", s->qscale);
-av_log(s->avctx, AV_LOG_INFO, "the value of qp is %d", s->qscale);
-av_log(s->avctx, AV_LOG_INFO, "the value of qp is %d", s->qscale);

Finally, in what place, i'm going to get the results ? (in the consol or in the log files?

Thank you kindly answer these three questions.

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