FFMPEG帧率设置总结

正常情况下可以通过AVCodecContext结构体中的time_base来设置帧率，如下设置帧率30

AVCodecContext* pVideoCtx = avcodec_alloc_context3(video_encoder);
pVideoCtx->time_base.num = 1;
pVideoCtx->time_base.den = 30;

但是有些情况设置不会有任何反应，那么可以通过下面两种方式配置：

1.在写包之前通过设置pts(设置帧率30)
packet->pts = packet->dts = packetCount * (ofmt_ctx->streams[0]->time_base.den) /ofmt_ctx->streams[0]->time_base.num / 30;

packetCount++;

av_interleaved_write_frame(ofmt_ctx, packet);

2.在写输出文件头的时候设置
AVDictionary* opt = NULL;
av_dict_set_int(&opt, "video_track_timescale", 25, 0);
avformat_write_header(ofmt_ctx, &opt);

AVDictionary *dictParam = 0;
av_dict_set(&dictParam, "preset", "medium", 0);
av_dict_set(&dictParam, "tune", "zerolatency", 0);
av_dict_set(&dictParam, "profile", "main", 0);
avcodec_open2(pVideoCtx, video_encoder, &dictParam );