ffmpeg实现视频切割

流程

打开输入——>打开输出——>根据输入来创建流——>拷贝流设置——>循环读帧——>判断时间点是否到达切割点，并做设置——>设置pts和dts——>写入——>善后

代码

  1. /* 
  2. *最简单的视频切割 
  3. *本程序实现把一个视频切割为2个视频，不涉及编解码，最难理解的地方在于pts和dts的计算，要好好看看 
  4. *不够完美的地方在于没有按照关键帧切割，所以会在切割点花屏，以后改善 
  5. *注：只处理一个视频流和一个音频流，若流多了，估计会crash 
  6. */  
  8. #include "stdafx.h"  
  10. #ifdef __cplusplus  
  11. extern"C"  
  12. {  
  13. #endif  
  14. #include <libavformat/avformat.h>  
  15. #include "libavcodec/avcodec.h"  
  16. #include "libavfilter/avfiltergraph.h"  
  17. #include "libavfilter/buffersink.h"  
  18. #include "libavfilter/buffersrc.h"  
  19. #include "libavutil/avutil.h"  
  20. #include "libavutil/opt.h"  
  21. #include "libavutil/pixdesc.h"  
  22. #include "libswresample\swresample.h"  
  23. #include "libavutil\fifo.h"  
  24. #include "libavutil/audio_fifo.h"  
  27. #pragma comment(lib, "avcodec.lib")  
  28. #pragma comment(lib, "avformat.lib")  
  29. #pragma comment(lib, "avutil.lib")  
  30. //#pragma comment(lib, "avdevice.lib")  
  31. #pragma comment(lib, "avfilter.lib")  
  32. //#pragma comment(lib, "postproc.lib")  
  33. #pragma comment(lib, "swresample.lib")  
  34. //#pragma comment(lib, "swscale.lib")  
  35. #ifdef __cplusplus  
  36. };  
  37. #endif  
  40. int _tmain(int argc, _TCHAR* argv[])  
  41. {  
  42.     if(argc < 3)  
  43.     {  
  44.         printf("no input file!\n");  
  45.         return -1;  
  46.     }  
  47.     AVFormatContext *ifmt_ctx = NULL, *ofmt1_ctx = NULL, *ofmt2_ctx = NULL;  
  48.     AVStream *out1_vstream = NULL, *out1_astream = NULL;  
  49.     AVStream *out2_vstream = NULL, *out2_astream = NULL;  
  50.     char str_out1_filename[10];  
  51.     char str_out2_filename[10];  
  52.     sprintf(str_out1_filename, "test1.%s", argv[2]);  
  53.     sprintf(str_out2_filename, "test2.%s", argv[2]);  
  55.     int inVideo_StreamIndex = -1,inAudio_StreamIndex = -1;  
  56.     int ret;  
  58.     av_register_all();  
  60.     if ((ret = avformat_open_input(&ifmt_ctx, argv[1], NULL, NULL)) < 0)  
  61.     {  
  62.         printf("can not open the in put file format context!\n");  
  63.         return -1;  
  64.     }  
  65.     if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0)  
  66.     {  
  67.         printf("can not find the input stream info!\n");  
  68.         goto end;  
  69.     }  
  71.     avformat_alloc_output_context2(&ofmt1_ctx, NULL, NULL, str_out1_filename);  
  72.     if (!ofmt1_ctx)  
  73.     {  
  74.         printf( "Could not create output1 context\n");  
  75.         ret = AVERROR_UNKNOWN;  
  76.         goto end;  
  77.     }  
  79.     avformat_alloc_output_context2(&ofmt2_ctx, NULL, NULL, str_out2_filename);  
  80.     if (!ofmt2_ctx)  
  81.     {  
  82.         printf( "Could not create output2 context\n");  
  83.         ret = AVERROR_UNKNOWN;  
  84.         goto end;  
  85.     }  
  87.     for (int i = 0; i < ifmt_ctx->nb_streams; i++)  
  88.     {  
  89.         if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)  
  90.         {  
  91.             inVideo_StreamIndex = i;  
  92.             out1_vstream = avformat_new_stream(ofmt1_ctx, NULL);  
  93.             out2_vstream = avformat_new_stream(ofmt2_ctx, NULL);  
  95.             //open decoder  
  96.             if(0 > avcodec_open2(ifmt_ctx->streams[i]->codec, avcodec_find_decoder(ifmt_ctx->streams[i]->codec->codec_id), NULL))  
  97.             {  
  98.                 printf("can not find or open video decoder!\n");  
  99.                 goto end;  
  100.             }  
  102.             if (!out1_vstream)  
  103.             {  
  104.                 printf("Failed allocating output1 video stream\n");  
  105.                 ret = AVERROR_UNKNOWN;  
  106.                 goto end;  
  107.             }  
  108.             else  
  109.             {  
  110.                 //copy the settings of AVCodecContext;  
  111.                 if (avcodec_copy_context(out1_vstream->codec, ifmt_ctx->streams[i]->codec) < 0)  
  112.                 {  
  113.                     printf( "Failed to copy context from input to output stream codec context\n");  
  114.                     goto end;  
  115.                 }  
  116.                 out1_vstream->codec->codec_tag = 0;  
  117.                 if(ofmt1_ctx->oformat->flags & AVFMT_GLOBALHEADER)  
  118.                 {  
  119.                     out1_vstream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;  
  120.                 }  
  121.             }  
  123.             if (!out2_vstream)  
  124.             {  
  125.                 printf("Failed allocating output1 video stream\n");  
  126.                 ret = AVERROR_UNKNOWN;  
  127.                 goto end;  
  128.             }  
  129.             else  
  130.             {  
  131.                 //copy the settings of AVCodecContext;  
  132.                 if (avcodec_copy_context(out2_vstream->codec, ifmt_ctx->streams[i]->codec) < 0)  
  133.                 {  
  134.                     printf( "Failed to copy context from input to output stream codec context\n");  
  135.                     goto end;  
  136.                 }  
  137.                 out2_vstream->codec->codec_tag = 0;  
  138.                 if(ofmt2_ctx->oformat->flags & AVFMT_GLOBALHEADER)  
  139.                 {  
  140.                     out2_vstream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;  
  141.                 }  
  142.             }  
  143.         }  
  144.         else if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)  
  145.         {  
  146.             inAudio_StreamIndex = i;  
  147.             out1_astream = avformat_new_stream(ofmt1_ctx, NULL);  
  148.             out2_astream = avformat_new_stream(ofmt2_ctx, NULL);  
  150.             if (!out1_astream)  
  151.             {  
  152.                 printf("Failed allocating output1 video stream\n");  
  153.                 ret = AVERROR_UNKNOWN;  
  154.                 goto end;  
  155.             }  
  156.             else  
  157.             {  
  158.                 //copy the settings of AVCodecContext;  
  159.                 if (avcodec_copy_context(out1_astream->codec, ifmt_ctx->streams[i]->codec) < 0)  
  160.                 {  
  161.                     printf( "Failed to copy context from input to output stream codec context\n");  
  162.                     goto end;  
  163.                 }  
  164.                 out1_astream->codec->codec_tag = 0;  
  165.                 if(ofmt1_ctx->oformat->flags & AVFMT_GLOBALHEADER)  
  166.                 {  
  167.                     out1_astream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;  
  168.                 }  
  169.             }  
  172.             if (!out2_astream)  
  173.             {  
  174.                 printf("Failed allocating output1 video stream\n");  
  175.                 ret = AVERROR_UNKNOWN;  
  176.                 goto end;  
  177.             }  
  178.             else  
  179.             {  
  180.                 //copy the settings of AVCodecContext;  
  181.                 if (avcodec_copy_context(out2_astream->codec, ifmt_ctx->streams[i]->codec) < 0)  
  182.                 {  
  183.                     printf( "Failed to copy context from input to output stream codec context\n");  
  184.                     goto end;  
  185.                 }  
  186.                 out2_astream->codec->codec_tag = 0;  
  187.                 if(ofmt2_ctx->oformat->flags & AVFMT_GLOBALHEADER)  
  188.                 {  
  189.                     out2_astream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;  
  190.                 }  
  191.             }  
  192.         }  
  193.     }  
  195.     //Dump Format------------------  
  196.     printf("\n==============Input Video=============\n");  
  197.     av_dump_format(ifmt_ctx, 0, argv[1], 0);  
  198.     printf("\n==============Output1============\n");  
  199.     av_dump_format(ofmt1_ctx, 0, str_out1_filename, 1);  
  200.     printf("\n==============Output2============\n");  
  201.     av_dump_format(ofmt2_ctx, 0, str_out1_filename, 1);  
  202.     printf("\n======================================\n");  
  204.     //open output1 file  
  205.     if (!(ofmt1_ctx->oformat->flags & AVFMT_NOFILE))  
  206.     {  
  207.         if (avio_open(&ofmt1_ctx->pb, str_out1_filename, AVIO_FLAG_WRITE) < 0)  
  208.         {  
  209.             printf( "Could not open output file '%s'", str_out1_filename);  
  210.             goto end;  
  211.         }  
  212.     }  
  214.     //open output2 file  
  215.     if (!(ofmt2_ctx->oformat->flags & AVFMT_NOFILE))  
  216.     {  
  217.         if (avio_open(&ofmt2_ctx->pb, str_out2_filename, AVIO_FLAG_WRITE) < 0)  
  218.         {  
  219.             printf( "Could not open output file '%s'", str_out2_filename);  
  220.             goto end;  
  221.         }  
  222.     }  
  224.     //write out 1 file header  
  225.     if (avformat_write_header(ofmt1_ctx, NULL) < 0)  
  226.     {  
  227.         printf( "Error occurred when opening video output file\n");  
  228.         goto end;  
  229.     }  
  231.     //write out 2 file header  
  232.     if (avformat_write_header(ofmt2_ctx, NULL) < 0)  
  233.     {  
  234.         printf( "Error occurred when opening video output file\n");  
  235.         goto end;  
  236.     }  
  237.     int splitPtsV = 0;//the real split video pts  
  238.     int splitDtsV = 0;  
  239.     int splitPtsA = 0;//the real split audio pts  
  240.     int splitDtsA = 0;  
  241.     int videoIndex = 0;//the real video index  
  243.     int splitTime = 30;//the split time (sec)  
  245.     AVPacket pkt;  
  246.     while(1)  
  247.     {  
  248.         AVFormatContext *ofmt_ctx;  
  249.         AVStream *in_stream, *out_stream;  
  250.         if (av_read_frame(ifmt_ctx, &pkt) < 0)  
  251.         {  
  252.             break;  
  253.         }  
  254.         in_stream = ifmt_ctx->streams[pkt.stream_index];  
  256.         if (pkt.stream_index == inVideo_StreamIndex)  
  257.         {  
  258.             videoIndex++;  
  259.             int time = pkt.pts * (((float)in_stream->time_base.num) / ((float)in_stream->time_base.den));  
  260.             if (time <= splitTime)  
  261.             {  
  262.                 splitPtsV = pkt.pts;  
  263.                 splitDtsV = pkt.dts;                  
  264.                 out_stream = ofmt1_ctx->streams[pkt.stream_index];  
  265.                 ofmt_ctx = ofmt1_ctx;  
  266.             }  
  267.             else  
  268.             {  
  269.                 pkt.pts = pkt.pts - splitPtsV;  
  270.                 pkt.dts = pkt.dts - splitDtsV;  
  271.                 out_stream = ofmt2_ctx->streams[pkt.stream_index];  
  272.                 ofmt_ctx = ofmt2_ctx;  
  273.             }  
  274.         }  
  275.         else if (pkt.stream_index == inAudio_StreamIndex)  
  276.         {  
  277.             int time = pkt.pts * (((float)in_stream->time_base.num) / ((float)in_stream->time_base.den));  
  278.             if (time <= splitTime)  
  279.             {  
  280.                 splitPtsA = pkt.pts;  
  281.                 splitDtsA = pkt.dts;  
  283.                 out_stream = ofmt1_ctx->streams[pkt.stream_index];  
  284.                 ofmt_ctx = ofmt1_ctx;  
  285.             }  
  286.             else  
  287.             {     
  288.                 pkt.pts = pkt.pts - splitPtsA;  
  289.                 pkt.dts = pkt.dts - splitDtsA;  
  291.                 out_stream = ofmt2_ctx->streams[pkt.stream_index];  
  292.                 ofmt_ctx = ofmt2_ctx;  
  293.             }  
  294.         }  
  296.         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));  
  297.         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));  
  298.         pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);  
  299.         pkt.pos = -1;  
  301.         //write into file  
  302.         if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0)  
  303.         {  
  304.             printf( "Error muxing packet\n");  
  305.             break;  
  306.         }  
  308.         av_free_packet(&pkt);  
  309.     }  
  311.     av_write_trailer(ofmt1_ctx);  
  312.     av_write_trailer(ofmt2_ctx);  
  314. end:  
  315.     avformat_close_input(&ifmt_ctx);  
  317.     /* close output */  
  318.     if (ofmt1_ctx && !(ofmt1_ctx->oformat->flags & AVFMT_NOFILE))  
  319.         avio_close(ofmt1_ctx->pb);  
  321.     avformat_free_context(ofmt1_ctx);  
  323.     /* close output */  
  324.     if (ofmt2_ctx && !(ofmt2_ctx->oformat->flags & AVFMT_NOFILE))  
  325.         avio_close(ofmt2_ctx->pb);  
  327.     avformat_free_context(ofmt2_ctx);  
  329.     return 0;  
  330. }

ffmpeg实现视频合并

流程

打开输入——>打开输出——>根据输入来创建流——>拷贝流设置——>循环读帧——>判断第一个读完，改输入为第二个——>设置pts和dts——>写入——>善后

代码

  1. /* 
  2. *最简单的视频合并 
  3. *本程序实现把2个视频合并为一个视频，不涉及编解码，但是对视频源有要求，必须是相同的参数 
  4. *着重理解第二个视频开始的时候的pts和dts计算 
  5. *注：只处理一个视频流和一个音频流，若流多了，估计会crash 
  6. */  
  8. #include "stdafx.h"  
  10. #ifdef __cplusplus  
  11. extern"C"  
  12. {  
  13. #endif  
  14. #include <libavformat/avformat.h>  
  15. #include "libavcodec/avcodec.h"  
  16. #include "libavfilter/avfiltergraph.h"  
  17. #include "libavfilter/buffersink.h"  
  18. #include "libavfilter/buffersrc.h"  
  19. #include "libavutil/avutil.h"  
  20. #include "libavutil/opt.h"  
  21. #include "libavutil/pixdesc.h"  
  22. #include "libswresample\swresample.h"  
  23. #include "libavutil\fifo.h"  
  24. #include "libavutil/audio_fifo.h"  
  27. #pragma comment(lib, "avcodec.lib")  
  28. #pragma comment(lib, "avformat.lib")  
  29. #pragma comment(lib, "avutil.lib")  
  30.     //#pragma comment(lib, "avdevice.lib")  
  31. #pragma comment(lib, "avfilter.lib")  
  32.     //#pragma comment(lib, "postproc.lib")  
  33. #pragma comment(lib, "swresample.lib")  
  34.     //#pragma comment(lib, "swscale.lib")  
  35. #ifdef __cplusplus  
  36. };  
  37. #endif  
  39. AVFormatContext *in1_fmtctx = NULL, *in2_fmtctx = NULL, *out_fmtctx = NULL;  
  40. AVStream *out_video_stream = NULL, *out_audio_stream = NULL;  
  41. int video_stream_index = -1, audio_stream_index = -1;  
  44. int open_input(const char * in1_name, const char * in2_name)  
  45. {  
  46.     int ret = -1;  
  47.     if ((ret = avformat_open_input(&in1_fmtctx, in1_name, NULL, NULL)) < 0)  
  48.     {  
  49.         printf("can not open the first input context!\n");  
  50.         return ret;  
  51.     }  
  52.     if ((ret = avformat_find_stream_info(in1_fmtctx, NULL)) < 0)  
  53.     {  
  54.         printf("can not find the first input stream info!\n");  
  55.         return ret;  
  56.     }  
  58.     if ((ret = avformat_open_input(&in2_fmtctx, in2_name, NULL, NULL)) < 0)  
  59.     {  
  60.         printf("can not open the first input context!\n");  
  61.         return ret;  
  62.     }  
  63.     if ((ret = avformat_find_stream_info(in2_fmtctx, NULL)) < 0)  
  64.     {  
  65.         printf("can not find the second input stream info!\n");  
  66.         return ret;  
  67.     }  
  68. }  
  70. int open_output(const char * out_name)  
  71. {  
  72.     int ret = -1;  
  73.     if ((ret = avformat_alloc_output_context2(&out_fmtctx, NULL, NULL, out_name)) < 0)  
  74.     {  
  75.         printf("can not alloc context for output!\n");  
  76.         return ret;  
  77.     }  
  79.     //new stream for out put  
  80.     for (int i = 0; i < in1_fmtctx->nb_streams; i++)  
  81.     {  
  82.         if (in1_fmtctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)  
  83.         {  
  84.             video_stream_index = i;  
  85.             out_video_stream = avformat_new_stream(out_fmtctx, NULL);  
  86.             if (!out_video_stream)  
  87.             {  
  88.                 printf("Failed allocating output1 video stream\n");  
  89.                 ret = AVERROR_UNKNOWN;  
  90.                 return ret;  
  91.             }  
  92.             if ((ret = avcodec_copy_context(out_video_stream->codec, in1_fmtctx->streams[i]->codec)) < 0)  
  93.             {  
  94.                 printf("can not copy the video codec context!\n");  
  95.                 return ret;  
  96.             }  
  97.             out_video_stream->codec->codec_tag = 0;  
  98.             if(out_fmtctx->oformat->flags & AVFMT_GLOBALHEADER)  
  99.             {  
  100.                 out_video_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;  
  101.             }  
  102.         }  
  103.         else if (in1_fmtctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)  
  104.         {  
  105.             audio_stream_index = i;  
  106.             out_audio_stream = avformat_new_stream(out_fmtctx, NULL);  
  108.             if (!out_audio_stream)  
  109.             {  
  110.                 printf("Failed allocating output1 video stream\n");  
  111.                 ret = AVERROR_UNKNOWN;  
  112.                 return ret;  
  113.             }  
  114.             if ((ret = avcodec_copy_context(out_audio_stream->codec, in1_fmtctx->streams[i]->codec)) < 0)  
  115.             {  
  116.                 printf("can not copy the video codec context!\n");  
  117.                 return ret;  
  118.             }  
  119.             out_audio_stream->codec->codec_tag = 0;  
  120.             if(out_fmtctx->oformat->flags & AVFMT_GLOBALHEADER)  
  121.             {  
  122.                 out_audio_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;  
  123.             }  
  124.         }  
  125.     }  
  127.     //open output file  
  128.     if (!(out_fmtctx->oformat->flags & AVFMT_NOFILE))  
  129.     {  
  130.         if ((ret = avio_open(&out_fmtctx->pb, out_name, AVIO_FLAG_WRITE)) < 0)  
  131.         {  
  132.             printf("can not open the out put file handle!\n");  
  133.             return ret;  
  134.         }  
  135.     }  
  137.     //write out  file header  
  138.     if ((ret = avformat_write_header(out_fmtctx, NULL)) < 0)  
  139.     {  
  140.         printf( "Error occurred when opening video output file\n");  
  141.         return ret;  
  142.     }  
  143. }  
  145. int _tmain(int argc, _TCHAR* argv[])  
  146. {  
  147.     if(argc < 4)  
  148.     {  
  149.         printf("no input file!\n");  
  150.         return -1;  
  151.     }  
  152.     char out_name[20];  
  153.     sprintf(out_name, "combine.%s", argv[3]);  
  154.     av_register_all();    
  155.     if (0 > open_input(argv[1], argv[2]))  
  156.     {  
  157.         goto end;  
  158.     }  
  160.     if(0 > open_output(out_name))  
  161.     {  
  162.         goto end;  
  163.     }  
  165.     AVFormatContext *input_ctx = in1_fmtctx;  
  166.     AVPacket pkt;  
  167.     int pts_v, pts_a, dts_v, dts_a;  
  168.     while(1)  
  169.     {  
  170.         if(0 > av_read_frame(input_ctx, &pkt))  
  171.         {  
  172.             if (input_ctx == in1_fmtctx)  
  173.             {  
  174.                 float vedioDuraTime, audioDuraTime;  
  176.                 //calc the first media dura time  
  177.                 vedioDuraTime = ((float)input_ctx->streams[video_stream_index]->time_base.num /   
  178.                     (float)input_ctx->streams[video_stream_index]->time_base.den) * ((float)pts_v);  
  179.                 audioDuraTime = ((float)input_ctx->streams[audio_stream_index]->time_base.num /   
  180.                     (float)input_ctx->streams[audio_stream_index]->time_base.den) * ((float)pts_a);  
  182.                 //calc the pts and dts end of the first media  
  183.                 if (audioDuraTime > vedioDuraTime)  
  184.                 {  
  185.                     dts_v = pts_v = audioDuraTime / ((float)input_ctx->streams[video_stream_index]->time_base.num /   
  186.                         (float)input_ctx->streams[video_stream_index]->time_base.den);  
  187.                     dts_a++;  
  188.                     pts_a++;  
  189.                 }  
  190.                 else  
  191.                 {  
  192.                     dts_a = pts_a = vedioDuraTime / ((float)input_ctx->streams[audio_stream_index]->time_base.num /   
  193.                         (float)input_ctx->streams[audio_stream_index]->time_base.den);  
  194.                     dts_v++;  
  195.                     pts_v++;  
  196.                 }  
  197.                 input_ctx = in2_fmtctx;  
  198.                 continue;  
  199.             }  
  200.             break;  
  201.         }  
  203.         if (pkt.stream_index == video_stream_index)  
  204.         {  
  205.             if (input_ctx == in2_fmtctx)  
  206.             {  
  207.                 pkt.pts += pts_v;  
  208.                 pkt.dts += dts_v;  
  209.             }  
  210.             else  
  211.             {  
  212.                 pts_v = pkt.pts;  
  213.                 dts_v = pkt.dts;  
  214.             }  
  215.         }  
  216.         else if (pkt.stream_index == audio_stream_index)  
  217.         {  
  218.             if (input_ctx == in2_fmtctx)  
  219.             {  
  220.                 pkt.pts += pts_a;  
  221.                 pkt.dts += dts_a;  
  222.             }  
  223.             else  
  224.             {  
  225.                 pts_a = pkt.pts;  
  226.                 dts_a = pkt.dts;  
  227.             }  
  228.         }  
  230.         pkt.pts = av_rescale_q_rnd(pkt.pts, input_ctx->streams[pkt.stream_index]->time_base,   
  231.             out_fmtctx->streams[pkt.stream_index]->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));  
  232.         pkt.dts = av_rescale_q_rnd(pkt.dts, input_ctx->streams[pkt.stream_index]->time_base,   
  233.             out_fmtctx->streams[pkt.stream_index]->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));  
  234.         pkt.pos = -1;  
  236.         if (av_interleaved_write_frame(out_fmtctx, &pkt) < 0)   
  237.         {  
  238.             printf( "Error muxing packet\n");  
  239.             //break;  
  240.         }  
  241.         av_free_packet(&pkt);         
  242.     }  
  244.     av_write_trailer(out_fmtctx);  
  246. end:  
  247.     avformat_close_input(&in1_fmtctx);  
  248.     avformat_close_input(&in2_fmtctx);  
  250.     /* close output */  
  251.     if (out_fmtctx && !(out_fmtctx->oformat->flags & AVFMT_NOFILE))  
  252.         avio_close(out_fmtctx->pb);  
  254.     avformat_free_context(out_fmtctx);  
  256.     return 0;  
  257. }

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