本文介紹一個簡單的基於FFmpeg的轉碼器。它可以將一種視訊格式（包括封轉格式和編碼格式）轉換為另一種視訊格式。轉碼器在視音訊編解碼處理的程式中，屬於一個比較複雜的東西。因為它結合了視訊的解碼和編碼。一個視訊播放器，一般只包含解碼功能；一個視訊編碼工具，一般只包含編碼功能；而一個視訊轉碼器，則需要先對視訊進行解碼，然後再對視訊進行編碼，因而相當於解碼器和編碼器的結合。下圖例舉了一個視訊的轉碼流程。輸入視訊的封裝格式是FLV，視訊編碼標準是H.264，音訊編碼標準是AAC；輸出視訊的封裝格式是AVI，視訊編碼標準是MPEG2，音訊編碼標準是MP3。從流程中可以看出，首先從輸入視訊中分離出視訊碼流和音訊壓縮碼流，然後分別將視訊碼流和音訊碼流進行解碼，獲取到非壓縮的畫素資料/音訊取樣資料，接著將非壓縮的畫素資料/音訊取樣資料重新進行編碼，獲得重新編碼後的視訊碼流和音訊碼流，最後將視訊碼流和音訊碼流重新封裝成一個檔案。

本文介紹的視訊轉碼器正是使用FFMPEG類庫從程式設計的角度實現了上述流程。該例子是從FFmpeg的例子改編的，平臺是VC2010，類庫版本是2014.5.6。

流程圖（2014.9.29更新）

下面附兩張使用FFmpeg轉碼視訊的流程圖。圖中使用淺綠色標出了視訊的編碼、解碼函式。從程式碼中可以看出，使用了AVFilter的不少東西，因此建議先學習AVFilter的內容後再看這個轉碼器的原始碼。

PS：實際上，轉碼器不是一定依賴AVFilter的。因此打算有時間對這個轉碼器進行進一步的簡化，使學習的人無需AVFilter的基礎也可以理解轉碼器。

簡單介紹一下流程中各個函式的意義：open_input_file()：開啟輸入檔案，並初始化相關的結構體。open_output_file()：開啟輸出檔案，並初始化相關的結構體。init_filters()：初始化AVFilter相關的結構體。av_read_frame()：從輸入檔案中讀取一個AVPacket。avcodec_decode_video2()：解碼一個視訊AVPacket（儲存H.264等壓縮碼流資料）為AVFrame（儲存YUV等非壓縮的畫素資料）。avcodec_decode_video4()：解碼一個音訊AVPacket（儲存MP3等壓縮碼流資料）為AVFrame（儲存PCM取樣資料）。filter_encode_write_frame()：編碼一個AVFrame。flush_encoder()：輸入檔案讀取完畢後，輸出編碼器中剩餘的AVPacket。

以上函式中open_input_file()，open_output_file()，init_filters()中的函式在其他文章中都有所敘述，在這裡不再重複：

在這裡介紹一下其中編碼的函式filter_encode_write_frame()。filter_encode_write_frame()函式的流程如下圖所示，它完成了視訊/音訊的編碼功能。

PS：視訊和音訊的編碼流程中除了編碼函式avcodec_encode_video2()和avcodec_encode_audio2()不一樣之外，其他部分幾乎完全一樣。

簡單介紹一下filter_encode_write_frame()中各個函式的意義：

av_buffersrc_add_frame()：將解碼後的AVFrame加入Filtergraph。

av_buffersink_get_buffer_ref()：從Filtergraph中取一個AVFrame。

avcodec_encode_video2()：編碼一個視訊AVFrame為AVPacket。

avcodec_encode_audio2()：編碼一個音訊AVFrame為AVPacket。

av_interleaved_write_frame()：將編碼後的AVPacket寫入檔案。

程式碼

貼上程式碼

/* *最簡單的基於FFmpeg的轉碼器 *Simplest FFmpeg Transcoder * *雷霄驊 Lei Xiaohua *[email protected] *中國傳媒大學/數字電視技術 *Communication University of China / DigitalTV Technology *http://blog.csdn.net/leixiaohua1020 * *本程式實現了視訊格式之間的轉換。是一個最簡單的視訊轉碼程式。 * */ #include "stdafx.h"extern "C"{#include "libavcodec/avcodec.h"#include "libavformat/avformat.h"#include "libavfilter/avfiltergraph.h"#include "libavfilter/avcodec.h"#include "libavfilter/buffersink.h"#include "libavfilter/buffersrc.h"#include "libavutil/avutil.h"#include "libavutil/opt.h"#include "libavutil/pixdesc.h"};   static AVFormatContext *ifmt_ctx;static AVFormatContext *ofmt_ctx;typedef struct FilteringContext{    AVFilterContext*buffersink_ctx;    AVFilterContext*buffersrc_ctx;    AVFilterGraph*filter_graph;} FilteringContext;static FilteringContext *filter_ctx;static int open_input_file(const char *filename){    int ret;    unsigned int i;    ifmt_ctx =NULL;    if ((ret = avformat_open_input(&ifmt_ctx,filename, NULL, NULL)) < 0) {       av_log(NULL, AV_LOG_ERROR, "Cannot openinput file\n");        return ret;    }    if ((ret = avformat_find_stream_info(ifmt_ctx, NULL))< 0) {       av_log(NULL, AV_LOG_ERROR, "Cannot findstream information\n");        return ret;    }    for (i = 0; i < ifmt_ctx->nb_streams; i++) {        AVStream*stream;       AVCodecContext *codec_ctx;        stream =ifmt_ctx->streams[i];        codec_ctx =stream->codec;        /* Reencode video & audio and remux subtitles etc. */        if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO                ||codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {            /* Open decoder */            ret =avcodec_open2(codec_ctx,                   avcodec_find_decoder(codec_ctx->codec_id), NULL);            if (ret < 0) {               av_log(NULL, AV_LOG_ERROR, "Failed toopen decoder for stream #%u\n", i);                return ret;            }        }    }   av_dump_format(ifmt_ctx, 0, filename, 0);    return 0;}static int open_output_file(const char *filename){    AVStream*out_stream;    AVStream*in_stream;    AVCodecContext*dec_ctx, *enc_ctx;    AVCodec*encoder;    int ret;    unsigned int i;    ofmt_ctx =NULL;   avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, filename);    if (!ofmt_ctx) {       av_log(NULL, AV_LOG_ERROR, "Could notcreate output context\n");        return AVERROR_UNKNOWN;    }    for (i = 0; i < ifmt_ctx->nb_streams; i++) {        out_stream= avformat_new_stream(ofmt_ctx, NULL);        if (!out_stream) {           av_log(NULL, AV_LOG_ERROR, "Failedallocating output stream\n");            return AVERROR_UNKNOWN;        }        in_stream =ifmt_ctx->streams[i];        dec_ctx =in_stream->codec;        enc_ctx =out_stream->codec;        if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO                ||dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {            /* in this example, we choose transcoding to same codec */            encoder= avcodec_find_encoder(dec_ctx->codec_id);            /* In this example, we transcode to same properties(picture size,            * sample rate etc.). These properties can be changed for output            * streams easily using filters */            if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {               enc_ctx->height = dec_ctx->height;               enc_ctx->width = dec_ctx->width;               enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;                /* take first format from list of supported formats */               enc_ctx->pix_fmt = encoder->pix_fmts[0];                /* video time_base can be set to whatever is handy andsupported by encoder */               enc_ctx->time_base = dec_ctx->time_base;            } else {               enc_ctx->sample_rate = dec_ctx->sample_rate;               enc_ctx->channel_layout = dec_ctx->channel_layout;               enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);                /* take first format from list of supported formats */               enc_ctx->sample_fmt = encoder->sample_fmts[0];                AVRationaltime_base={1, enc_ctx->sample_rate};               enc_ctx->time_base = time_base;            }            /* Third parameter can be used to pass settings to encoder*/            ret =avcodec_open2(enc_ctx, encoder, NULL);            if (ret < 0) {               av_log(NULL, AV_LOG_ERROR, "Cannot openvideo encoder for stream #%u\n", i);                return ret;            }        } else if(dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) {           av_log(NULL, AV_LOG_FATAL, "Elementarystream #%d is of unknown type, cannot proceed\n", i);            return AVERROR_INVALIDDATA;        } else {            /* if this stream must be remuxed */            ret =avcodec_copy_context(ofmt_ctx->streams[i]->codec,                   ifmt_ctx->streams[i]->codec);            if (ret < 0) {               av_log(NULL, AV_LOG_ERROR, "Copyingstream context failed\n");                return ret;            }        }        if (ofmt_ctx->oformat->flags &AVFMT_GLOBALHEADER)           enc_ctx->flags |= CODEC_FLAG_GLOBAL_HEADER;    }   av_dump_format(ofmt_ctx, 0, filename, 1);    if (!(ofmt_ctx->oformat->flags &AVFMT_NOFILE)) {        ret =avio_open(&ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Could notopen output file '%s'", filename);            return ret;        }    }    /* init muxer, write output file header */    ret =avformat_write_header(ofmt_ctx, NULL);    if (ret < 0) {        av_log(NULL,AV_LOG_ERROR, "Error occurred when openingoutput file\n");        return ret;    }    return 0;}static intinit_filter(FilteringContext* fctx, AVCodecContext *dec_ctx,       AVCodecContext *enc_ctx, const char *filter_spec){    char args[512];    int ret = 0;    AVFilter*buffersrc = NULL;    AVFilter*buffersink = NULL;    AVFilterContext*buffersrc_ctx = NULL;    AVFilterContext*buffersink_ctx = NULL;    AVFilterInOut*outputs = avfilter_inout_alloc();    AVFilterInOut*inputs  = avfilter_inout_alloc();    AVFilterGraph*filter_graph = avfilter_graph_alloc();    if (!outputs || !inputs || !filter_graph) {        ret =AVERROR(ENOMEM);        goto end;    }    if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {        buffersrc =avfilter_get_by_name("buffer");        buffersink= avfilter_get_by_name("buffersink");        if (!buffersrc || !buffersink) {           av_log(NULL, AV_LOG_ERROR, "filteringsource or sink element not found\n");            ret = AVERROR_UNKNOWN;            goto end;        }       _snprintf(args, sizeof(args),                "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",               dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,                dec_ctx->time_base.num,dec_ctx->time_base.den,               dec_ctx->sample_aspect_ratio.num,               dec_ctx->sample_aspect_ratio.den);        ret =avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",               args, NULL, filter_graph);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannotcreate buffer source\n");            goto end;        }        ret =avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",               NULL, NULL, filter_graph);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannotcreate buffer sink\n");            goto end;        }        ret =av_opt_set_bin(buffersink_ctx, "pix_fmts",               (uint8_t*)&enc_ctx->pix_fmt, sizeof(enc_ctx->pix_fmt),               AV_OPT_SEARCH_CHILDREN);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannot setoutput pixel format\n");            goto end;        }    } else if(dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {        buffersrc = avfilter_get_by_name("abuffer");        buffersink= avfilter_get_by_name("abuffersink");        if (!buffersrc || !buffersink) {           av_log(NULL, AV_LOG_ERROR, "filteringsource or sink element not found\n");            ret =AVERROR_UNKNOWN;            goto end;        }        if (!dec_ctx->channel_layout)           dec_ctx->channel_layout =               av_get_default_channel_layout(dec_ctx->channels);       _snprintf(args, sizeof(args),                "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%I64x",               dec_ctx->time_base.num, dec_ctx->time_base.den,dec_ctx->sample_rate,               av_get_sample_fmt_name(dec_ctx->sample_fmt),               dec_ctx->channel_layout);        ret =avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",               args, NULL, filter_graph);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannotcreate audio buffer source\n");            goto end;        }        ret =avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",               NULL, NULL, filter_graph);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannotcreate audio buffer sink\n");            goto end;        }        ret = av_opt_set_bin(buffersink_ctx, "sample_fmts",               (uint8_t*)&enc_ctx->sample_fmt, sizeof(enc_ctx->sample_fmt),               AV_OPT_SEARCH_CHILDREN);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannot setoutput sample format\n");            goto end;        }        ret =av_opt_set_bin(buffersink_ctx, "channel_layouts",               (uint8_t*)&enc_ctx->channel_layout,                sizeof(enc_ctx->channel_layout),AV_OPT_SEARCH_CHILDREN);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannot setoutput channel layout\n");            goto end;        }        ret =av_opt_set_bin(buffersink_ctx, "sample_rates",               (uint8_t*)&enc_ctx->sample_rate, sizeof(enc_ctx->sample_rate),               AV_OPT_SEARCH_CHILDREN);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Cannot setoutput sample rate\n");            goto end;        }    } else {        ret =AVERROR_UNKNOWN;        goto end;    }    /* Endpoints for the filter graph. */   outputs->name       =av_strdup("in");   outputs->filter_ctx = buffersrc_ctx;   outputs->pad_idx    = 0;   outputs->next       = NULL;   inputs->name       = av_strdup("out");   inputs->filter_ctx = buffersink_ctx;   inputs->pad_idx    = 0;   inputs->next       = NULL;    if (!outputs->name || !inputs->name) {        ret =AVERROR(ENOMEM);        goto end;    }    if ((ret = avfilter_graph_parse_ptr(filter_graph,filter_spec,                   &inputs, &outputs, NULL)) < 0)        goto end;    if ((ret = avfilter_graph_config(filter_graph, NULL))< 0)        goto end;    /* Fill FilteringContext */   fctx->buffersrc_ctx = buffersrc_ctx;   fctx->buffersink_ctx = buffersink_ctx;    fctx->filter_graph= filter_graph;end:   avfilter_inout_free(&inputs);   avfilter_inout_free(&outputs);    return ret;}static int init_filters(void){    const char*filter_spec;    unsigned int i;    int ret;    filter_ctx =(FilteringContext *)av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));    if (!filter_ctx)        return AVERROR(ENOMEM);    for (i = 0; i < ifmt_ctx->nb_streams; i++) {       filter_ctx[i].buffersrc_ctx  =NULL;        filter_ctx[i].buffersink_ctx= NULL;       filter_ctx[i].filter_graph   =NULL;        if(!(ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO                ||ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO))            continue;        if (ifmt_ctx->streams[i]->codec->codec_type== AVMEDIA_TYPE_VIDEO)           filter_spec = "null"; /* passthrough (dummy) filter for video */        else           filter_spec = "anull"; /* passthrough (dummy) filter for audio */        ret =init_filter(&filter_ctx[i], ifmt_ctx->streams[i]->codec,               ofmt_ctx->streams[i]->codec, filter_spec);        if (ret)            return ret;    }    return 0;}static intencode_write_frame(AVFrame *filt_frame, unsignedint stream_index, int*got_frame) {    int ret;    int got_frame_local;    AVPacketenc_pkt;    int (*enc_func)(AVCodecContext *, AVPacket *, const AVFrame *, int*) =       (ifmt_ctx->streams[stream_index]->codec->codec_type ==        AVMEDIA_TYPE_VIDEO) ? avcodec_encode_video2 : avcodec_encode_audio2;    if (!got_frame)        got_frame =&got_frame_local;    av_log(NULL,AV_LOG_INFO, "Encoding frame\n");    /* encode filtered frame */    enc_pkt.data =NULL;    enc_pkt.size =0;    av_init_packet(&enc_pkt);    ret =enc_func(ofmt_ctx->streams[stream_index]->codec, &enc_pkt,           filt_frame, got_frame);   av_frame_free(&filt_frame);    if (ret < 0)        return ret;    if (!(*got_frame))        return 0;    /* prepare packet for muxing */   enc_pkt.stream_index = stream_index;    enc_pkt.dts =av_rescale_q_rnd(enc_pkt.dts,           ofmt_ctx->streams[stream_index]->codec->time_base,           ofmt_ctx->streams[stream_index]->time_base,           (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));    enc_pkt.pts =av_rescale_q_rnd(enc_pkt.pts,           ofmt_ctx->streams[stream_index]->codec->time_base,           ofmt_ctx->streams[stream_index]->time_base,           (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));   enc_pkt.duration = av_rescale_q(enc_pkt.duration,           ofmt_ctx->streams[stream_index]->codec->time_base,           ofmt_ctx->streams[stream_index]->time_base);    av_log(NULL,AV_LOG_DEBUG, "Muxing frame\n");    /* mux encoded frame */    ret =av_interleaved_write_frame(ofmt_ctx, &enc_pkt);    return ret;}static intfilter_encode_write_frame(AVFrame *frame, unsignedint stream_index){    int ret;    AVFrame*filt_frame;    av_log(NULL,AV_LOG_INFO, "Pushing decoded frame tofilters\n");    /* push the decoded frame into the filtergraph */    ret =av_buffersrc_add_frame_flags(filter_ctx[stream_index].buffersrc_ctx,            frame,0);    if (ret < 0) {       av_log(NULL, AV_LOG_ERROR, "Error whilefeeding the filtergraph\n");        return ret;    }    /* pull filtered frames from the filtergraph */    while (1) {        filt_frame= av_frame_alloc();        if (!filt_frame) {            ret =AVERROR(ENOMEM);            break;        }       av_log(NULL, AV_LOG_INFO, "Pullingfiltered frame from filters\n");        ret =av_buffersink_get_frame(filter_ctx[stream_index].buffersink_ctx,               filt_frame);        if (ret < 0) {            /* if nomore frames for output - returns AVERROR(EAGAIN)            * if flushed and no more frames for output - returns AVERROR_EOF            * rewrite retcode to 0 to show it as normal procedure completion            */            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)                ret= 0;           av_frame_free(&filt_frame);            break;        }       filt_frame->pict_type = AV_PICTURE_TYPE_NONE;        ret =encode_write_frame(filt_frame, stream_index, NULL);        if (ret < 0)            break;    }    return ret;}static int flush_encoder(unsigned intstream_index){    int ret;    int got_frame;    if(!(ofmt_ctx->streams[stream_index]->codec->codec->capabilities&               CODEC_CAP_DELAY))        return 0;    while (1) {       av_log(NULL, AV_LOG_INFO, "Flushingstream #%u encoder\n", stream_index);        ret =encode_write_frame(NULL, stream_index, &got_frame);        if (ret < 0)            break;        if (!got_frame)            return 0;    }    return ret;} int_tmain(int argc, _TCHAR* argv[]){    int ret;    AVPacketpacket;    AVFrame *frame= NULL;    enum AVMediaType type;    unsigned intstream_index;    unsigned int i;    int got_frame;    int (*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket*);    if (argc != 3) {       av_log(NULL, AV_LOG_ERROR, "Usage: %s<input file> <output file>\n", argv[0]);        return 1;    }   av_register_all();   avfilter_register_all();    if ((ret = open_input_file(argv[1])) < 0)        goto end;    if ((ret = open_output_file(argv[2])) < 0)        goto end;    if ((ret = init_filters()) < 0)        goto end;    /* read all packets */    while (1) {        if ((ret= av_read_frame(ifmt_ctx, &packet)) < 0)            break;       stream_index = packet.stream_index;        type =ifmt_ctx->streams[packet.stream_index]->codec->codec_type;       av_log(NULL, AV_LOG_DEBUG, "Demuxergave frame of stream_index %u\n",               stream_index);        if (filter_ctx[stream_index].filter_graph) {           av_log(NULL, AV_LOG_DEBUG, "Going toreencode&filter the frame\n");            frame =av_frame_alloc();            if (!frame) {                ret = AVERROR(ENOMEM);                break;            }           packet.dts = av_rescale_q_rnd(packet.dts,                   ifmt_ctx->streams[stream_index]->time_base,                   ifmt_ctx->streams[stream_index]->codec->time_base,                    (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));           packet.pts = av_rescale_q_rnd(packet.pts,                   ifmt_ctx->streams[stream_index]->time_base,                   ifmt_ctx->streams[stream_index]->codec->time_base,                   (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));           dec_func = (type == AVMEDIA_TYPE_VIDEO) ? avcodec_decode_video2 :               avcodec_decode_audio4;            ret =dec_func(ifmt_ctx->streams[stream_index]->codec, frame,                   &got_frame, &packet);            if (ret < 0) {               av_frame_free(&frame);               av_log(NULL, AV_LOG_ERROR, "Decodingfailed\n");                break;            }            if (got_frame) {               frame->pts = av_frame_get_best_effort_timestamp(frame);                ret= filter_encode_write_frame(frame, stream_index);               av_frame_free(&frame);                if (ret< 0)                   goto end;            } else {               av_frame_free(&frame);            }        } else {            /* remux this frame without reencoding */           packet.dts = av_rescale_q_rnd(packet.dts,                   ifmt_ctx->streams[stream_index]->time_base,                   ofmt_ctx->streams[stream_index]->time_base,                    (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));           packet.pts = av_rescale_q_rnd(packet.pts,                   ifmt_ctx->streams[stream_index]->time_base,                   ofmt_ctx->streams[stream_index]->time_base,                    (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));            ret =av_interleaved_write_frame(ofmt_ctx, &packet);            if (ret < 0)                goto end;        }       av_free_packet(&packet);    }    /* flush filters and encoders */    for (i = 0; i < ifmt_ctx->nb_streams; i++) {        /* flush filter */        if (!filter_ctx[i].filter_graph)            continue;        ret =filter_encode_write_frame(NULL, i);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Flushingfilter failed\n");            goto end;        }        /* flush encoder */        ret = flush_encoder(i);        if (ret < 0) {           av_log(NULL, AV_LOG_ERROR, "Flushingencoder failed\n");            goto end;        }    }   av_write_trailer(ofmt_ctx);end:   av_free_packet(&packet);   av_frame_free(&frame);    for (i = 0; i < ifmt_ctx->nb_streams; i++) {       avcodec_close(ifmt_ctx->streams[i]->codec);        if (ofmt_ctx && ofmt_ctx->nb_streams >i && ofmt_ctx->streams[i] &&ofmt_ctx->streams[i]->codec)           avcodec_close(ofmt_ctx->streams[i]->codec);        if(filter_ctx && filter_ctx[i].filter_graph)           avfilter_graph_free(&filter_ctx[i].filter_graph);    }   av_free(filter_ctx);   avformat_close_input(&ifmt_ctx);    if (ofmt_ctx &&!(ofmt_ctx->oformat->flags & AVFMT_NOFILE))        avio_close(ofmt_ctx->pb);   avformat_free_context(ofmt_ctx);    if (ret < 0)       av_log(NULL, AV_LOG_ERROR, "Erroroccurred\n");    return (ret? 1:0);}

程式執行截圖：

預設情況下執行程式，會將“cuc_ieschool.ts”轉換為“cuc_ieschool.avi”。除錯的時候，可以修改“配置屬性->除錯->命令引數”中的引數，即可改變轉碼的輸入輸出檔案。