简单的ffmpeg视频转码，只处理视频

1、简单说下整体流程

用avformat_open_input打开输入文件上下文，再用avformat_find_stream_info找到流信息，为输出分配AVFormatContext空间，然后根据流信息找到视频流，为输出创建流，并打开编解码器，写输出文件头，然后一个循环读帧---解码----压缩----写入，然后flush_encoder，最后写文件尾，释放资源----结束。

2、贴上代码

/**最简单的视频转码器（只处理视频）*缪国凯 Mickel*[e-mail]*本程序实现从一个视频格式转码到另一个视频格式，只处理视频，音频忽略*2015-5-7*/#include "stdafx.h"#ifdef __cplusplusextern"C"{#endif#include <libavformat/avformat.h>#ifdef __cplusplus};#endifint flush_encoder(AVFormatContext *fmt_ctx, unsigned int stream_index);int _tmain(int argc, _TCHAR* argv[]){AVFormatContext *in_fmt_ctx = NULL, *out_fmt_ctx = NULL;AVStream *out_stream = NULL;AVFrame *frame;AVPacket pkt_in, pkt_out;int video_index = -1;if (argc < 3){printf("error in input param");getchar();return -1;}av_register_all();//inputif (avformat_open_input(&in_fmt_ctx, argv[1], NULL, NULL) < 0){printf("can not open input file context");goto end;}if (avformat_find_stream_info(in_fmt_ctx, NULL) < 0){printf("can not find input stream info!\n");goto end;}//outputavformat_alloc_output_context2(&out_fmt_ctx, NULL, NULL, argv[2]);if (!out_fmt_ctx){printf("can not alloc output context!\n");goto end;}//open decoder & new out stream & open encoderfor (int i = 0; i < in_fmt_ctx->nb_streams; i++){if (in_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO){//open decoderif(0 > avcodec_open2(in_fmt_ctx->streams[i]->codec, avcodec_find_decoder(in_fmt_ctx->streams[i]->codec->codec_id), NULL)){printf("can not find or open decoder!\n");goto end;}video_index = i;//new streamout_stream = avformat_new_stream(out_fmt_ctx, NULL);if (!out_stream){printf("can not new stream for output!\n");goto end;}//set codec context paramout_stream->codec->codec = avcodec_find_encoder(out_fmt_ctx->oformat->video_codec);out_stream->codec->height = in_fmt_ctx->streams[i]->codec->height;out_stream->codec->width = in_fmt_ctx->streams[i]->codec->width;//I do not know why the input file time_base is not correct//out_stream->codec->time_base = in_fmt_ctx->streams[i]->codec->time_base;out_stream->codec->time_base.num = in_fmt_ctx->streams[i]->avg_frame_rate.den;out_stream->codec->time_base.den = in_fmt_ctx->streams[i]->avg_frame_rate.num;out_stream->codec->sample_aspect_ratio = in_fmt_ctx->streams[i]->codec->sample_aspect_ratio;// take first format from list of supported formatsout_stream->codec->pix_fmt = in_fmt_ctx->streams[i]->codec->pix_fmt;out_stream->codec->pix_fmt = out_stream->codec->codec->pix_fmts[0];//open encoderif (!out_stream->codec->codec){printf("can not find the encoder!\n");goto end;}if ((avcodec_open2(out_stream->codec, out_stream->codec->codec, NULL)) < 0){printf("can not open the encoder\n");goto end;}if (out_fmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;break;}}if (-1 == video_index){printf("found no video stream in input file!\n");goto end;}if (!(out_fmt_ctx->oformat->flags & AVFMT_NOFILE)){if(avio_open(&out_fmt_ctx->pb, argv[2], AVIO_FLAG_WRITE) < 0){printf("can not open output file handle!\n");goto end;}}if(avformat_write_header(out_fmt_ctx, NULL) < 0){printf("can not write the header of the output file!\n");goto end;}av_init_packet(&pkt_in);av_init_packet(&pkt_out);frame = av_frame_alloc();int got_frame, got_picture;int frame_index = 0;int i = 0;while(1){got_frame = -1;got_picture = -1;pkt_in.data = NULL;pkt_in.size = 0;if (av_read_frame(in_fmt_ctx, &pkt_in) < 0){break;}if (avcodec_decode_video2(in_fmt_ctx->streams[video_index]->codec, frame, &got_frame, &pkt_in) < 0){printf("can not decoder a frame");break;}av_free_packet(&pkt_in);if (got_frame){frame->pts = i++;pkt_out.data = NULL;pkt_out.size = 0;if (avcodec_encode_video2(out_stream->codec, &pkt_out, frame, &got_picture) < 0){printf("can not encode aframe!\n");break;}if (got_picture){printf("Succeed to encode frame: %5d\tsize:%5d\n",frame_index,pkt_out.size);pkt_out.stream_index = out_stream->index;// pkt_out.dts = av_rescale_q_rnd(pkt_out.dts,// out_fmt_ctx->streams[video_index]->codec->time_base,// out_fmt_ctx->streams[video_index]->time_base,// (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));// pkt_out.pts = av_rescale_q_rnd(pkt_out.pts,// out_fmt_ctx->streams[video_index]->codec->time_base,// out_fmt_ctx->streams[video_index]->time_base,// (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));// pkt_out.duration = av_rescale_q(pkt_out.duration,// out_fmt_ctx->streams[video_index]->codec->time_base,// out_fmt_ctx->streams[video_index]->time_base);frame_index++;av_write_frame(out_fmt_ctx, &pkt_out);av_free_packet(&pkt_out);}}}av_frame_free(&frame);int ret = flush_encoder(out_fmt_ctx, 0);if (ret < 0){printf("Flushing encoder failed");return -1;}//write file trailerav_write_trailer(out_fmt_ctx);//cleanavcodec_close(out_stream->codec);avcodec_close(in_fmt_ctx->streams[video_index]->codec);end:avformat_close_input(&in_fmt_ctx);if (out_fmt_ctx && !(out_fmt_ctx->oformat->flags & AVFMT_NOFILE)){avio_close(out_fmt_ctx->pb);}avformat_free_context(out_fmt_ctx);return 0;}int flush_encoder(AVFormatContext *fmt_ctx, unsigned int stream_index){int ret;int got_frame;AVPacket enc_pkt;if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &CODEC_CAP_DELAY)){return 0;}while(1){enc_pkt.data = NULL;enc_pkt.size = 0;av_init_packet(&enc_pkt);ret = avcodec_encode_video2(fmt_ctx->streams[stream_index]->codec, &enc_pkt, NULL, &got_frame);av_frame_free(NULL);if (ret < 0){break;}if (!got_frame){ret = 0;break;}printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n",enc_pkt.size);/* mux encoded frame */ret = av_write_frame(fmt_ctx, &enc_pkt);if (ret < 0)break;}return ret;}

3、工程下载地址

http://download.csdn.net/detail/dancing_night/8671679