ffmpeg 的 tbr tbc 和 tbn的意义
ffmpeg -i video.flv Stream #0.0[0x1e0]: Video: mpeg2video, yuv420p, 704x576 [PAR 12:11 DAR 4:3], 9578 kb/s, 25 tbr, 90k tbn, 50 tbc
tbn = the time base in AVStream that has come from the container tbc = the time base in AVCodecContext for the codec used for a particular stream tbr = tbr is guessed from the video stream and is the value users want to see when they look for the video frame rate
不是所有参数都能得到的,有的文件没有这些信息,要看解析层而定。
代码如下:
25 tbr代表帧率;
代码如下:
1 if(st->codec->codec_type == CODEC_TYPE_VIDEO){ 2 if(st->r_frame_rate.den && st->r_frame_rate.num) 3 print_fps(av_q2d(st->r_frame_rate), "tbr"); 4 if(st->time_base.den && st->time_base.num) 5 print_fps(1/av_q2d(st->time_base), "tbn"); 6 if(st->codec->time_base.den && st->codec->time_base.num) 7 print_fps(1/av_q2d(st->codec->time_base), "tbc"); 8 }
25 tbr代表帧率;
90k tbn代表文件层(st)的时间精度,即1S=1200k,和duration相关;
50 tbc代表视频层(st->codec)的时间精度,即1S=50,和strem->duration和时间戳相关。