整体方案：
采集端：摄像头采集（YUV）->编码（YUV转H264）->写封装（Ｈ264转FLV）->RTMP推流
客户端：RTMP拉流->解封装（FLV转H264）->解码（H264转YUV）->YUV显示（SDL2）
程序：

推流时要启动服务器，方法在前面章节有描述

#include <stdio.h>#define __STDC_CONSTANT_MACROS#ifdef _WIN32
//Windows
extern "C"
{
#include "libavformat/avformat.h"
#include "libavutil/mathematics.h"
#include "libavutil/time.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavformat/avformat.h>
#include <libavutil/mathematics.h>
#include <libavutil/time.h>
#ifdef __cplusplus
};
#endif
#endifint main(int argc, char* argv[])
{AVOutputFormat *ofmt = NULL;//输入对应一个AVFormatContext，输出对应一个AVFormatContext//（Input AVFormatContext and Output AVFormatContext）AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;AVPacket pkt;const char *in_filename, *out_filename;int ret, i;int videoindex=-1;int frame_index=0;int64_t start_time=0;in_filename  = "demo.flv";//输入URL（Input file URL）out_filename = "rtmp://192.168.6.139:1935/live/stream";//输出 URL（Output URL）[RTMP]av_register_all();//Networkavformat_network_init();//输入（Input）if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {printf( "Could not open input file.");goto end;}if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {printf( "Failed to retrieve input stream information");goto end;}for(i=0; i<ifmt_ctx->nb_streams; i++) if(ifmt_ctx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){videoindex=i;break;}av_dump_format(ifmt_ctx, 0, in_filename, 0);//输出（Output）avformat_alloc_output_context2(&ofmt_ctx, NULL, "flv", out_filename); //RTMP//avformat_alloc_output_context2(&ofmt_ctx, NULL, "mpegts", out_filename);//UDPif (!ofmt_ctx) {printf( "Could not create output context\n");ret = AVERROR_UNKNOWN;goto end;}ofmt = ofmt_ctx->oformat;for (i = 0; i < ifmt_ctx->nb_streams; i++) {//根据输入流创建输出流（Create output AVStream according to input AVStream）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;}//复制AVCodecContext的设置（Copy the settings of AVCodecContext）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 |= AV_CODEC_FLAG_GLOBAL_HEADER;}//Dump Format------------------av_dump_format(ofmt_ctx, 0, out_filename, 1);//打开输出URL（Open output URL）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（Write file header）ret = avformat_write_header(ofmt_ctx, NULL);if (ret < 0) {printf( "Error occurred when opening output URL\n");goto end;}start_time=av_gettime();while (1) {AVStream *in_stream, *out_stream;//获取一个AVPacket（Get an AVPacket）ret = av_read_frame(ifmt_ctx, &pkt);if (ret < 0)break;//FIX：No PTS (Example: Raw H.264)//Simple Write PTSif(pkt.pts==AV_NOPTS_VALUE){//Write PTSAVRational time_base1=ifmt_ctx->streams[videoindex]->time_base;//Duration between 2 frames (us)int64_t calc_duration=(double)AV_TIME_BASE/av_q2d(ifmt_ctx->streams[videoindex]->r_frame_rate);//Parameterspkt.pts=(double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE);pkt.dts=pkt.pts;pkt.duration=(double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE);}//Important:Delayif(pkt.stream_index==videoindex){AVRational time_base=ifmt_ctx->streams[videoindex]->time_base;AVRational time_base_q={1,AV_TIME_BASE};int64_t pts_time = av_rescale_q(pkt.dts, time_base, time_base_q);int64_t now_time = av_gettime() - start_time;if (pts_time > now_time)av_usleep(pts_time - now_time);}in_stream  = ifmt_ctx->streams[pkt.stream_index];out_stream = ofmt_ctx->streams[pkt.stream_index];/* copy packet *///转换PTS/DTS（Convert PTS/DTS）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));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));pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);pkt.pos = -1;//Print to Screenif(pkt.stream_index==videoindex){printf("Send %8d video frames to output URL\n",frame_index);frame_index++;}//ret = av_write_frame(ofmt_ctx, &pkt);ret = av_interleaved_write_frame(ofmt_ctx, &pkt);if (ret < 0) {printf( "Error muxing packet\n");break;}av_free_packet(&pkt);}//写文件尾（Write file trailer）av_write_trailer(ofmt_ctx);
end:avformat_close_input(&ifmt_ctx);/* close output */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 occurred.\n");return -1;}return 0;
}