* This example stream local media files to streaming media ，server (Use RTMP as example)，It's the simplest FFmpeg streamer. source from [雷霄骅](http://blog.csdn.net/leixiaohua1020)

simplest_ffmpeg_streamer.c

#include <stdio.h>
#include <libavformat/avformat.h>
#include <libavutil/mathematics.h>
#include <libavutil/time.h>

int 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;
	
	//in_filename  = "cuc_ieschool.mov";
	//in_filename  = "cuc_ieschool.mkv";
	//in_filename  = "cuc_ieschool.ts";
	//in_filename  = "cuc_ieschool.mp4";
	//in_filename  = "cuc_ieschool.h264";
	in_filename  = argv[1];//输入URL（Input file URL）
	//in_filename  = "shanghai03_p.h264";
	
//	out_filename = "rtmp://localhost:1935/live1/553";//输出 URL（Output URL）[RTMP]
	out_filename = "rtp://192.168.8.155:6666";//输出 URL（Output URL）[UDP]

	av_register_all();
	//Network
	avformat_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;
	}

	int videoindex=-1;
	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);//UDP

	if (!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 |= 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;
	}

	int frame_index=0;

	int64_t 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 PTS
		if(pkt.pts==AV_NOPTS_VALUE){
			//Write PTS
			AVRational 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);
			//Parameters
			pkt.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:Delay
		if(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, (AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
		pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (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 Screen
		if(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;
}

/*
* build script:
* gcc -o simplest_ffmpeg_streamer simplest_ffmpeg_streamer.c `pkg-config --cflags --libs  libswscale libavformat libavfilter libavutil libavresample libswresample libavcodec` 
*/

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