[FFmpeg-devel] Modify the source code of FFmpeg-"fprintf ()"-"av_log ()" - standard output-

[Moad Toutou]

Hello,
I would like to modify the source code of FFmpeg. I would like to display on the console (standard output) messages and values​​.
 I tried to use the  fprintf () function of C language, but:  when i compile the files, there are error messages.The error message displays :"please use av_log () function"

However, I looked at the file log.c and log.h but I have not managed to get good information.
I want to know first, if it is possible to add instructions in the ffmpeg code to display values ​​or messages in the console (standard output)?

If YES, what is the equivalent of the following instructions:

1 - fprintf ("I am a comment");
2-fprintf ("the quantization parameter equal  %d", qp);

If NOT (that is to say, we can not view information about the console), so, where i could get these messages and these values​​? (I feel they are stored in the particular files, that is to say: they have a different output of standard output, Is this true?)


Frankly, a big thank  for your answers.

Sincerely, 
--
Toufik