log_callback     3627 fftools/ffprobe.c         av_log_set_callback(log_callback);
log_callback      427 libavutil/log.c     void (*log_callback)(void*, int, const char*, va_list) = av_log_callback;
log_callback      431 libavutil/log.c     if (log_callback)
log_callback      432 libavutil/log.c         log_callback(avcl, level, fmt, vl);