ffmpeg更改视频的帧率

note

视频帧率调整
    帧率(fps-frame per second)
    例如：原来帧率为30，调整后为1   现象：原来是每秒有30张图像，调整后每秒1张图像，看着图像很慢
    实现：在每秒的时间区间里，取一张图像

version

#define LIBAVFILTER_VERSION_MINOR 12

#define LIBAVFILTER_VERSION_MICRO 100

#define LIBAVCODEC_VERSION_MINOR 31

#define LIBAVCODEC_VERSION_MICRO 102

code

void CFfmpegOps::ChangeVideoFPS(const char *in_mp4, const char *out_mp4)
{AVFormatContext *in_fmt_ctx = nullptr;const AVInputFormat *in_fmt = nullptr;AVFormatContext *out_fmt_ctx = nullptr;const AVOutputFormat *out_fmt = nullptr;int ret = -1;int video_stream_index = 0;const AVCodec *decoder = nullptr;AVCodecContext *decoder_ctx = nullptr;const AVCodec* encoder = nullptr;AVCodecContext* encoder_ctx = nullptr;AVStream* in_avstream = nullptr;AVStream* out_avstream = nullptr;const AVFilter * avfilter_buffer_src = nullptr; // 源，video buffer可设置的参数有AVFilterContext* avfilter_ctx_buffer_src = nullptr;const AVFilter * avfilter_fps = nullptr;    // 中间节点，video fps可设置的参数包含fpsAVFilterContext* avfilter_ctx_fps = nullptr;const AVFilter* avfilter_buffer_sink = nullptr; // 终，video buffersink可设置的参数只有pixel formatsAVFilterContext* avfilter_ctx_buffer_sink = nullptr;AVFilterGraph* avfiltergraph = nullptr;AVPacket* avpacket_src = nullptr;AVFrame* avframe_src = nullptr;AVFrame* avframe_dest = nullptr;AVPacket* avpacket_dest = nullptr;AVRational pixel_aspect = {.num = 1, .den = 1};ret = avformat_open_input(&in_fmt_ctx, in_mp4, nullptr, nullptr);if (ret < 0){printf("avformat_open_input error(%s)\n", GetFfmpegERR(ret));goto END;}in_fmt = in_fmt_ctx->iformat;ret = avformat_find_stream_info(in_fmt_ctx, nullptr);if (ret < 0){printf("avformat_find_stream_info error(%s)\n", GetFfmpegERR(ret));goto END;}ret = av_find_best_stream(in_fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);if (ret < 0){printf("av_find_best_stream error(%s)\n", GetFfmpegERR(ret));goto END;}video_stream_index = ret;in_avstream = in_fmt_ctx->streams[video_stream_index];decoder = avcodec_find_decoder(in_avstream->codecpar->codec_id);if (!decoder){printf("avcodec_find_decoder error\n");goto END;}decoder_ctx = avcodec_alloc_context3(decoder);if (!decoder_ctx){printf("avcodec_alloc_context3 error\n");goto END;}ret = avcodec_parameters_to_context(decoder_ctx, in_avstream->codecpar);if (ret < 0){printf("avcodec_parameters_to_context error(%s)\n", GetFfmpegERR(ret));goto END;}ret = avcodec_open2(decoder_ctx, decoder, nullptr);if (ret < 0){printf("avcodec_open2 error(%s)\n", GetFfmpegERR(ret));goto END;}avfiltergraph = avfilter_graph_alloc();if (!avfiltergraph){printf("avfilter_graph_alloc error\n");goto END;}avfilter_buffer_src = avfilter_get_by_name("buffer");   // buffer对应video，abuffer对应audioif (!avfilter_buffer_src){printf("avfilter_get_by_name error\n");goto END;}printf("avfilter_buffer_src->desc:%s\n", avfilter_buffer_src->description);avfilter_ctx_buffer_src = avfilter_graph_alloc_filter(avfiltergraph, avfilter_buffer_src, avfilter_buffer_src->name);if (!avfilter_ctx_buffer_src){printf("avfilter_graph_alloc_filter error\n");goto END;}// 设置avfilter_ctx_buffer_src的可选参数// 参照libavfilter/buffersrc.c文件中对video buffer的可选参数描述ret = av_opt_set(avfilter_ctx_buffer_src, "width", std::to_string(in_avstream->codecpar->width).c_str(), AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}ret = av_opt_set(avfilter_ctx_buffer_src, "height", std::to_string(in_avstream->codecpar->height).c_str(), AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}ret = av_opt_set(avfilter_ctx_buffer_src, "pix_fmt", av_get_pix_fmt_name((AVPixelFormat)(in_avstream->codecpar->format)), AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}ret = av_opt_set_q(avfilter_ctx_buffer_src,"time_base", in_avstream->time_base,AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}ret = av_opt_set_q(avfilter_ctx_buffer_src,"frame_rate", in_avstream->r_frame_rate,AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}ret = av_opt_set_q(avfilter_ctx_buffer_src,"pixel_aspect", pixel_aspect,AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}// 上面已经设置过参数，初始化就不传参了ret = avfilter_init_str(avfilter_ctx_buffer_src, nullptr);if (ret < 0){printf("avfilter_init_str error(%s)\n", GetFfmpegERR(ret));goto END;}avfilter_fps = avfilter_get_by_name("fps");if (!avfilter_fps){printf("avfilter_get_by_name error\n");goto END;}printf("avfilter_fps->desc:%s\n", avfilter_fps->description);avfilter_ctx_fps = avfilter_graph_alloc_filter(avfiltergraph, avfilter_fps, avfilter_fps->name);if (!avfilter_ctx_fps){printf("avfilter_graph_alloc_filter error\n");goto END;}ret = av_opt_set(avfilter_ctx_fps, "fps", "1",AV_OPT_SEARCH_CHILDREN);if (ret < 0){printf("av_opt_set error(%s)\n", GetFfmpegERR(ret));goto END;}ret = avfilter_init_str(avfilter_ctx_fps, nullptr);if (ret < 0){printf("avfilter_init_str error(%s)\n", GetFfmpegERR(ret));goto END;}avfilter_buffer_sink = avfilter_get_by_name("buffersink");if (!avfilter_buffer_sink){printf("avfilter_get_by_name error\n");goto END;}printf("avfilter_buffer_sink->desc:%s\n", avfilter_buffer_sink->description);avfilter_ctx_buffer_sink = avfilter_graph_alloc_filter(avfiltergraph, avfilter_buffer_sink, avfilter_buffer_sink->name);if (!avfilter_ctx_buffer_sink){printf("avfilter_graph_alloc_filter error\n");goto END;}ret = avfilter_init_str(avfilter_ctx_buffer_sink, nullptr);if (ret < 0){printf("avfilter_init_str error(%s)\n", GetFfmpegERR(ret));goto END;}// 把avfilter组成链// avfilter_link的作用，在src和dest之间新建AVFilterLink实例// srcpad:src的输出通道编号// destpad:dest的输入通道编号ret = avfilter_link(avfilter_ctx_buffer_src, 0, avfilter_ctx_fps, 0);if (ret != 0){printf("avfilter_link error(%s)\n", GetFfmpegERR(ret));goto END;}ret = avfilter_link(avfilter_ctx_fps, 0, avfilter_ctx_buffer_sink, 0);if (ret != 0){printf("avfilter_link error(%s)\n", GetFfmpegERR(ret));goto END;}ret = avfilter_graph_config(avfiltergraph, nullptr);if (ret < 0){printf("avfilter_graph_config error(%s)\n", GetFfmpegERR(ret));goto END;}ret = avformat_alloc_output_context2(&out_fmt_ctx, nullptr, nullptr, out_mp4);if (ret < 0){printf("avformat_alloc_output_context2 error(%s)\n", GetFfmpegERR(ret));goto END;}out_fmt = out_fmt_ctx->oformat;encoder = avcodec_find_encoder(decoder->id);if (!encoder){printf("avcodec_find_encoder error\n");goto END;}encoder_ctx = avcodec_alloc_context3(encoder);if (!encoder_ctx){printf("avcodec_alloc_context3 error\n");goto END;}encoder_ctx->pix_fmt = (AVPixelFormat)(av_buffersink_get_format(avfilter_ctx_buffer_sink));encoder_ctx->width = av_buffersink_get_w(avfilter_ctx_buffer_sink);encoder_ctx->height = av_buffersink_get_h(avfilter_ctx_buffer_sink);encoder_ctx->time_base = av_buffersink_get_time_base(avfilter_ctx_buffer_sink);encoder_ctx->framerate = av_buffersink_get_frame_rate(avfilter_ctx_buffer_sink);encoder_ctx->gop_size = decoder_ctx->gop_size;encoder_ctx->max_b_frames = decoder_ctx->max_b_frames;if (out_fmt->flags & AVFMT_GLOBALHEADER){encoder_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;}ret = avcodec_open2(encoder_ctx, encoder, nullptr);if (ret < 0){printf("avcodec_open2 error(%s)\n", GetFfmpegERR(ret));goto END;}out_avstream = avformat_new_stream(out_fmt_ctx, encoder);if (!out_avstream){printf("avformat_new_stream error\n");goto END;}out_avstream->time_base = av_buffersink_get_time_base(avfilter_ctx_buffer_sink);out_avstream->r_frame_rate = av_buffersink_get_frame_rate(avfilter_ctx_buffer_sink);out_avstream->avg_frame_rate = av_buffersink_get_frame_rate(avfilter_ctx_buffer_sink);ret = avcodec_parameters_from_context(out_avstream->codecpar, encoder_ctx);if (ret < 0){printf("avcodec_parameters_from_context error(%s)\n", GetFfmpegERR(ret));goto END;}ret = avio_open(&(out_fmt_ctx->pb), out_mp4, AVIO_FLAG_WRITE);if (ret < 0){printf("avio_open error(%s)\n", GetFfmpegERR(ret));goto END;}// 调用avformat_write_header后，out_avstream的时间基发生了变化(10->102400)，容器要求?ret = avformat_write_header(out_fmt_ctx, nullptr);if (ret < 0){printf("avformat_write_header error(%s)\n", GetFfmpegERR(ret));goto END;}avpacket_src = av_packet_alloc();if (!avpacket_src){printf("av_packet_alloc error\n");goto END;}avpacket_dest = av_packet_alloc();if (!avpacket_dest){printf("av_packet_alloc error\n");goto END;}avframe_src = av_frame_alloc();if (!avframe_src){printf("av_frame_alloc error\n");goto END;}avframe_dest = av_frame_alloc();if (!avframe_dest){printf("av_frame_alloc error\n");goto END;}while (1){// 从输入文件读取压缩视频帧ret = av_read_frame(in_fmt_ctx, avpacket_src);if (ret < 0){printf("av_read_frame error(%s)\n", GetFfmpegERR(ret));break;}if (avpacket_src->stream_index != video_stream_index){av_packet_unref(avpacket_src);continue;}// 把压缩视频帧发送给解码器ret = avcodec_send_packet(decoder_ctx, avpacket_src);if (ret != 0){printf("avcodec_send_packet error(%s)\n", GetFfmpegERR(ret));}else{// 接收解码器的输出视频帧ret = avcodec_receive_frame(decoder_ctx, avframe_src);if (ret != 0){printf("avcodec_receive_frame error(%s)\n", GetFfmpegERR(ret));}else{// 把视频帧交给avfilterret = av_buffersrc_write_frame(avfilter_ctx_buffer_src, avframe_src);if (ret != 0){printf("av_buffersrc_write_frame error(%s)\n", GetFfmpegERR(ret));}else{// 从avfilter获取视频帧ret = av_buffersink_get_frame(avfilter_ctx_buffer_sink, avframe_dest);if (ret < 0){printf("av_buffersink_get_frame error(%s)\n", GetFfmpegERR(ret));}else{// 把视频帧交给编码器ret = avcodec_send_frame(encoder_ctx, avframe_dest);if (ret != 0){printf("avcodec_send_frame error(%s)\n", GetFfmpegERR(ret));}else{// 从编码器获取压缩视频帧ret = avcodec_receive_packet(encoder_ctx, avpacket_dest);if (ret != 0){printf("avcodec_receive_packet error(%s)\n", GetFfmpegERR(ret));}else{av_packet_rescale_ts(avpacket_dest, encoder_ctx->time_base, out_avstream->time_base);// 写入到输出文件ret = av_write_frame(out_fmt_ctx, avpacket_dest);if (ret < 0){printf("av_write_frame error(%s)\n", GetFfmpegERR(ret));}}}}}}}}ret = av_write_trailer(out_fmt_ctx);if (ret < 0){printf("av_write_trailer error(%s)\n", GetFfmpegERR(ret));goto END;}END:if (avframe_dest){av_frame_free(&avframe_dest);avframe_dest = nullptr;}if (avframe_src){av_frame_free(&avframe_src);avframe_src = nullptr;}if (avpacket_src){av_packet_free(&avpacket_src);avpacket_src = nullptr;}if (avpacket_dest){av_packet_free(&avpacket_dest);avpacket_dest = nullptr;}if (avfilter_ctx_buffer_sink){avfilter_free(avfilter_ctx_buffer_sink);avfilter_ctx_buffer_sink = nullptr;}if (avfilter_ctx_fps){avfilter_free(avfilter_ctx_fps);avfilter_ctx_fps = nullptr;}if (avfilter_ctx_buffer_src){avfilter_free(avfilter_ctx_buffer_src);avfilter_ctx_buffer_src = nullptr;}if (avfiltergraph){avfilter_graph_free(&avfiltergraph);avfiltergraph = nullptr;}if (encoder_ctx){avcodec_free_context(&encoder_ctx);encoder_ctx = nullptr;}if (decoder_ctx){avcodec_free_context(&decoder_ctx);decoder_ctx = nullptr;}if (out_fmt_ctx){avformat_free_context(out_fmt_ctx);out_fmt_ctx = nullptr;}if (in_fmt_ctx){avformat_free_context(in_fmt_ctx);in_fmt_ctx = nullptr;}
}

performance