FFMPEG 从rtsp抓取流，转存为flv文件

#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;
    
}

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