项目地址，求star
https://github.com/979451341/AudioVideoStudyCodeTwo/tree/master/FFmpeg%E7%BB%99%E8%A7%86%E9%A2%91%E6%8D%A2%E5%A3%B0%E9%9F%B3

一个视频有三个流，视频流，音频流，字幕流，我将视频A的视频流拿出来，将音乐B的音频流拿出来，合在一起成新的视频

还是老规矩直接说c代码如何运行

注册组件，打开并获得MP4文件和MP3文件的信息

av_register_all();//Inputif ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, 0, 0)) < 0) {//打开输入的视频文件 LOGE( "Could not open input file."); goto end;}if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {//获取视频文件信息 LOGE( "Failed to retrieve input stream information"); goto end;}if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, 0, 0)) < 0) {//打开输入的音频文件 LOGE( "Could not open input file."); goto end;}if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {//获取音频文件信息 LOGE( "Failed to retrieve input stream information"); goto end;}

创建输出文件

//Outputavformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);//初始化输出码流的AVFormatContext。if (!ofmt_ctx) { LOGE( "Could not create output context\n"); ret = AVERROR_UNKNOWN; return -1;}ofmt = ofmt_ctx->oformat;

获取MP4的视频流和MP3的音频流

//从输入的AVStream中获取一个输出的out_streamfor (i = 0; i < ifmt_ctx_v->nb_streams; i++) { //Create output AVStream according to input AVStream if(ifmt_ctx_v->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){ AVStream *in_stream = ifmt_ctx_v->streams[i]; AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);//创建流通道AVStream videoindex_v=i; if (!out_stream) { LOGE( "Failed allocating output stream\n"); ret = AVERROR_UNKNOWN; break; } videoindex_out=out_stream->index; //Copy the settings of AVCodecContext if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 0) { LOGE( "Failed to copy context from input to output stream codec context\n"); break; } out_stream->codec->codec_tag = 0; if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER) out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER; break; }}for (i = 0; i < ifmt_ctx_a->nb_streams; i++) { //Create output AVStream according to input AVStream if(ifmt_ctx_a->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO){ AVStream *in_stream = ifmt_ctx_a->streams[i]; AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec); audioindex_a=i; if (!out_stream) { LOGE( "Failed allocating output stream\n"); ret = AVERROR_UNKNOWN; goto end; } audioindex_out=out_stream->index; //Copy the settings of AVCodecContext if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 0) { LOGE( "Failed to copy context from input to output stream codec context\n"); goto end; } out_stream->codec->codec_tag = 0; if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER) out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER; break; }}

获取输出文件的信息并打开输出文件，获得输出流

LOGE("==========Output Information==========\n");av_dump_format(ofmt_ctx, 0, out_filename, 1);LOGE("======================================\n");//Open output fileif (!(ofmt->flags & AVFMT_NOFILE)) { if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE) < 0) {//打开输出文件。 LOGE( "Could not open output file '%s'", out_filename); return -1; }}//Write file headerif (avformat_write_header(ofmt_ctx, NULL) < 0) { LOGE( "Error occurred when opening output file\n"); return -1;}

接下来就是边解码边编码了，这个解码是解码视频流和音频流，这个两个流解码速度需要保持一致
这个通过双方时间轴来判断，然后就将解码的数据编码放入输出文件

//Get an AVPacket . av_compare_ts是比较时间戳用的。通过该函数可以决定该写入视频还是音频。 if(av_compare_ts(cur_pts_v,ifmt_ctx_v->streams[videoindex_v]->time_base,cur_pts_a,ifmt_ctx_a->streams[audioindex_a]->time_base) <= 0)

开始是先解码视频，放入cur_pts_v

if(av_read_frame(ifmt_ctx, &pkt) >= 0){ do{ in_stream = ifmt_ctx->streams[pkt.stream_index]; out_stream = ofmt_ctx->streams[stream_index]; if(pkt.stream_index==videoindex_v){ //FIX：No PTS (Example: Raw H.264) H.264裸流没有PTS，因此必须手动写入PTS //Simple Write PTS if(pkt.pts==AV_NOPTS_VALUE){ //Write PTS AVRational time_base1=in_stream->time_base; //Duration between 2 frames (us) int64_t calc_duration=(double)AV_TIME_BASE/av_q2d(in_stream->r_frame_rate); //Parameters pkt.pts=(double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE); pkt.dts=pkt.pts; pkt.duration=(double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE); frame_index++; } cur_pts_v=pkt.pts; break; } }while(av_read_frame(ifmt_ctx, &pkt) >= 0); }

接着是解码音频放入cur_pts_a

if(av_read_frame(ifmt_ctx, &pkt) >= 0){ do{ in_stream = ifmt_ctx->streams[pkt.stream_index]; out_stream = ofmt_ctx->streams[stream_index]; if(pkt.stream_index==audioindex_a){ //FIX：No PTS //Simple Write PTS if(pkt.pts==AV_NOPTS_VALUE){ //Write PTS AVRational time_base1=in_stream->time_base; //Duration between 2 frames (us) int64_t calc_duration=(double)AV_TIME_BASE/av_q2d(in_stream->r_frame_rate); //Parameters pkt.pts=(double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE); pkt.dts=pkt.pts; pkt.duration=(double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE); frame_index++; } cur_pts_a=pkt.pts; break; } }while(av_read_frame(ifmt_ctx, &pkt) >= 0); }else{ break; }

然后就是将之前解码的数据编码放入输出文件，释放这个pkt

//Convert PTS/DTS pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX)); pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX)); pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base); pkt.pos = -1; pkt.stream_index=stream_index; LOGE("Write 1 Packet. size:%5d\tpts:%lld\n",pkt.size,pkt.pts); //Write AVPacket 音频或视频裸流 if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0) { LOGE( "Error muxing packet\n"); break; }

av_free_packet(&pkt);

通过不断地循环，解码一下视频流，解码一下音频流，编码放入输出文件，这三个步骤不断循环完成合成视频

完成输出视频，并释放资源

//Write file trailerav_write_trailer(ofmt_ctx);

#if USE_H264BSF
av_bitstream_filter_close(h364bsfc);
#endif
#if USE_AACBSF
av_bitstream_filter_close(aacbsfc);
#endif

end:avformat_close_input(&ifmt_ctx_v);avformat_close_input(&ifmt_ctx_a);/* close output */if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE)) avio_close(ofmt_ctx->pb);avformat_free_context(ofmt_ctx);if (ret < 0 && ret != AVERROR_EOF) { LOGE( "Error occurred.\n"); return -1;}

下一次依旧与音频有关系