Implement the reading of the video bitrate of flv movies out of the meta data,

to have the total bitrate available in the avformat structures.
Patch by Stefan de Konink  stefan konink de

Originally committed as revision 16943 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/flvdec.c

@@ -187,6 +187,8 @@ static int amf_parse_object(AVFormatContext *s, AVStream *astream, AVStream *vst
             if(!strcmp(key, "duration")) s->duration = num_val * AV_TIME_BASE;
 //            else if(!strcmp(key, "width")  && vcodec && num_val > 0) vcodec->width  = num_val;
 //            else if(!strcmp(key, "height") && vcodec && num_val > 0) vcodec->height = num_val;
+            else if(!strcmp(key, "videodatarate") && vcodec && 0 <= (int)(num_val * 1024.0))
+                vcodec->bit_rate = num_val * 1024.0;
             else if(!strcmp(key, "audiocodecid") && acodec && 0 <= (int)num_val)
                 flv_set_audio_codec(s, astream, (int)num_val << FLV_AUDIO_CODECID_OFFSET);
             else if(!strcmp(key, "videocodecid") && vcodec && 0 <= (int)num_val)