FFMPEG 从rtsp抓取流，转存为flv文件

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 #include

 #define __STDC_CONSTANT_MACROS

 #ifdef __cplusplus
 extern "C"
 {
 #endif

 #include
 #include
 #include

 #ifdef __cplusplus
 }
 #endif


 int main(int argc,char **argv)
 {
     AVOutputFormat *ofmt = NULL;
     AVFormatContext *ifmt_ctx = NULL,*ofmt_ctx = NULL;
     AVPacket pkt;
     const char *in_filename,*out_filename;
     int ret,i;
     int video_index=-1;
     int frame_index=0;
     in_filename="rtsp://admin:[email protected]:554/";
     out_filename="receive.flv";

     av_register_all();
     avformat_network_init();

     //使用TCP连接打开RTSP，设置最大延迟时间
     AVDictionary *avdic=NULL;
     char option_key[]="rtsp_transport";
     char option_value[]="tcp";
     av_dict_set(&avdic,option_key,option_value,0);
     char option_key2[]="max_delay";
     char option_value2[]="5000000";
     av_dict_set(&avdic,option_key2,option_value2,0);
     //打开输入流
     if((ret=avformat_open_input(&ifmt_ctx,in_filename,0,&avdic))<0)
     {
         printf("Could not open input file.\n");
         goto end;
     }
     if((ret=avformat_find_stream_info(ifmt_ctx,0))<0)
     {
         printf("Failed to retrieve input stream information\n");
         goto end;
     }
     //nb_streams代表有几路流，一般是2路：即音频和视频，顺序不一定
     for(i=0;inb_streams;i++){

         if(ifmt_ctx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
         {
             //这一路是视频流，标记一下，以后取视频流都从ifmt_ctx->streams[video_index]取
             video_index=i;
             break;
         }
     }

     av_dump_format(ifmt_ctx,0,in_filename,0);

     //打开输出流
     avformat_alloc_output_context2(&ofmt_ctx,NULL,NULL,out_filename);

     if(!ofmt_ctx)
     {
         printf("Could not create output context\n");
         ret=AVERROR_UNKNOWN;
         goto end;
     }

     ofmt = ofmt_ctx->oformat;
     for(i=0;inb_streams;i++)
     {    //根据输入流创建输出流
         AVStream *in_stream = ifmt_ctx->streams[i];
         AVStream *out_stream = avformat_new_stream(ofmt_ctx,in_stream->codec->codec);
         if(!out_stream)
         {
             printf("Failed allocating output stream.\n");
             ret = AVERROR_UNKNOWN;
             goto end;
         }

         //将输出流的编码信息复制到输入流
         ret = avcodec_copy_context(out_stream->codec,in_stream->codec);
         if(ret<0)
         {
             printf("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;

     }

     //Dump format--------------------
     av_dump_format(ofmt_ctx,0,out_filename,1);
     //打开输出文件
     if(!(ofmt->flags & AVFMT_NOFILE))
     {
         ret = avio_open(&ofmt_ctx->pb,out_filename,AVIO_FLAG_WRITE);
         if(ret<0)
         {
             printf("Could not open output URL '%s'",out_filename);
             goto end;
         }
     }

     //写文件头到输出文件
     ret = avformat_write_header(ofmt_ctx,NULL);
     if(ret < 0)
     {
         printf("Error occured when opening output URL\n");
         goto end;
     }


     //while循环中持续获取数据包，不管音频视频都存入文件
     while(1)
     {
         AVStream *in_stream,*out_stream;
         //从输入流获取一个数据包
         ret = av_read_frame(ifmt_ctx,&pkt);
         if(ret<0)
             break;

         in_stream = ifmt_ctx->streams[pkt.stream_index];
         out_stream = ofmt_ctx->streams[pkt.stream_index];
         //copy packet
         //转换 PTS/DTS 时序
         pkt.pts = av_rescale_q_rnd(pkt.pts,in_stream->time_base,out_stream->time_base,(enum 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, (enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
         //printf("pts %d dts %d base %d\n",pkt.pts,pkt.dts, in_stream->time_base);
         pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
         pkt.pos = -1;

         //此while循环中并非所有packet都是视频帧，当收到视频帧时记录一下，仅此而已
         if(pkt.stream_index==video_index)
         {
             printf("Receive %8d video frames from input URL\n",frame_index);
             frame_index++;
         }

         //将包数据写入到文件。
         ret = av_interleaved_write_frame(ofmt_ctx,&pkt);
         if(ret < 0)
         {
             /**
             当网络有问题时，容易出现到达包的先后不一致，pts时序混乱会导致
             av_interleaved_write_frame函数报 -22 错误。暂时先丢弃这些迟来的帧吧
             若所大部分包都没有pts时序，那就要看情况自己补上时序（比如较前一帧时序+1）再写入。
             */
             if(ret==-22){
                 continue;
             }else{
                 printf("Error muxing packet.error code %d\n" , ret);
                 break;
             }

         }

         //av_free_packet(&pkt); //此句在新版本中已deprecated 由av_packet_unref代替
         av_packet_unref(&pkt);
     }


     //写文件尾
     av_write_trailer(ofmt_ctx);

 end:

     av_dict_free(&avdic);
     avformat_close_input(&ifmt_ctx);
     //Close input
     if(ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
         avio_close(ofmt_ctx->pb);
     avformat_free_context(ofmt_ctx);
     if(ret<0 && ret != AVERROR_EOF)
     {
         printf("Error occured.\n");
         return -1;
     }
     return 0;

 }