- 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:
- if(st->codec->codec_type == CODEC_TYPE_VIDEO){
- if(st->r_frame_rate.den && st->r_frame_rate.num)
- print_fps(av_q2d(st->r_frame_rate), "tbr");
- if(st->time_base.den && st->time_base.num)
- print_fps(1/av_q2d(st->time_base), "tbn");
- if(st->codec->time_base.den && st->codec->time_base.num)
- print_fps(1/av_q2d(st->codec->time_base), "tbc");
- }
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。
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