本文记录一个基于FFmpeg的视音频复用器（Simplest FFmpeg muxer）。视音频复用器（Muxer）即是将视频压缩数据（例如H.264）和音频压缩数据（例如AAC）合并到一个封装格式数据（例如MKV）中去。如图所示。在这个过程中并不涉及到编码和解码。

流程

代码

/**
 * 最简单的基于FFmpeg的视音频复用器
 * Simplest FFmpeg Muxer
 *
 * 雷霄骅 Lei Xiaohua
 * leixiaohua1020@126.com
 * 中国传媒大学/数字电视技术
 * Communication University of China / Digital TV Technology
 * http://blog.csdn.net/leixiaohua1020
 *
 * 本程序可以将视频码流和音频码流打包到一种封装格式中。
 * 程序中将MP3编码的音频码流和H.264编码（MPEG2TS封装中）的视频码流打包成
 * MP4封装格式的文件。
 * 需要注意的是本程序并不改变视音频的编码格式。
 *
 * This software mux a video bitstream and a audio bitstream 
 * together into a file.
 * In this example, it mux a H.264 bitstream (in MPEG2TS) and 
 * a MP3 bitstream file together into MP4 format file.
 *
 */

#include <stdio.h>

extern "C"
{
#include "libavformat/avformat.h"
};
/*
FIX: H.264 in some container format (FLV, MP4, MKV etc.) need 
"h264_mp4toannexb" bitstream filter (BSF)
  *Add SPS,PPS in front of IDR frame
  *Add start code ("0,0,0,1") in front of NALU
H.264 in some container (MPEG2TS) don‘t need this BSF.
*/
//‘1‘: Use H.264 Bitstream Filter 
#define USE_H264BSF 0

/*
FIX:AAC in some container format (FLV, MP4, MKV etc.) need 
"aac_adtstoasc" bitstream filter (BSF)
*/
//‘1‘: Use AAC Bitstream Filter 
#define USE_AACBSF 0



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_v = NULL, *ifmt_ctx_a = NULL,*ofmt_ctx = NULL;
	AVPacket pkt;
	int ret, i;
	
	char *in_filename_v = "cuc_ieschool.ts";//输入文件名（Input file URL）
	//char *in_filename_v = "cuc_ieschool.h264";
	//char *in_filename_a = "cuc_ieschool.mp3";
	//char *in_filename_a = "gowest.m4a";
	//char *in_filename_a = "gowest.aac";
	char *in_filename_a = "huoyuanjia.mp3";

	char *out_filename = "cuc_ieschool.mp4";//输出文件名（Output file URL）
	av_register_all();
	//输入（Input）
	if ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, 0, 0)) < 0) {
		printf( "Could not open input file.");
		goto end;
	}
	if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {
		printf( "Failed to retrieve input stream information");
		goto end;
	}

	if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, 0, 0)) < 0) {
		printf( "Could not open input file.");
		goto end;
	}
	if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {
		printf( "Failed to retrieve input stream information");
		goto end;
	}
	printf("Input Information=====================\n");
	av_dump_format(ifmt_ctx_v, 0, in_filename_v, 0);
	av_dump_format(ifmt_ctx_a, 0, in_filename_a, 0);
	printf("======================================\n");
	//输出（Output）
	avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
	if (!ofmt_ctx) {
		printf( "Could not create output context\n");
		ret = AVERROR_UNKNOWN;
		goto end;
	}
	ofmt = ofmt_ctx->oformat;
	int videoindex_v=-1,videoindex_out=-1;
	for (i = 0; i < ifmt_ctx_v->nb_streams; i++) {
		//根据输入流创建输出流（Create output AVStream according to input AVStream）
		if(ifmt_ctx_v->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
		videoindex_v=i;
		AVStream *in_stream = ifmt_ctx_v->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;
		}
		videoindex_out=out_stream->index;
		//复制AVCodecContext的设置（Copy the settings of AVCodecContext）
		if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 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;
		break;
		}
	}

	int audioindex_a=-1,audioindex_out=-1;
	for (i = 0; i < ifmt_ctx_a->nb_streams; i++) {
		//根据输入流创建输出流（Create output AVStream according to input AVStream）
		if(ifmt_ctx_a->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO){
			audioindex_a=i;
			AVStream *in_stream = ifmt_ctx_a->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;
			}
			audioindex_out=out_stream->index;
			//复制AVCodecContext的设置（Copy the settings of AVCodecContext）
			if (avcodec_copy_context(out_stream->codec, in_stream->codec) < 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;

			break;
		}
	}

	//输出一下格式------------------
	printf("Output Information====================\n");
	av_dump_format(ofmt_ctx, 0, out_filename, 1);
	printf("======================================\n");
	//打开输出文件（Open output file）
	if (!(ofmt->flags & AVFMT_NOFILE)) {
		if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE) < 0) {
			printf( "Could not open output file ‘%s‘", out_filename);
			goto end;
		}
	}
	//写文件头（Write file header）
	if (avformat_write_header(ofmt_ctx, NULL) < 0) {
		printf( "Error occurred when opening output file\n");
		goto end;
	}
	int frame_index=0;
	int64_t cur_pts_v=0,cur_pts_a=0;

	//FIX
#if USE_H264BSF
	AVBitStreamFilterContext* h264bsfc =  av_bitstream_filter_init("h264_mp4toannexb"); 
#endif
#if USE_AACBSF
	AVBitStreamFilterContext* aacbsfc =  av_bitstream_filter_init("aac_adtstoasc"); 
#endif

	while (1) {
		AVFormatContext *ifmt_ctx;
		int stream_index=0;
		AVStream *in_stream, *out_stream;


		//获取一个AVPacket（Get an AVPacket）
		if(av_compare_ts(cur_pts_v,ifmt_ctx_v->streams[videoindex_v]->time_base,cur_pts_a,ifmt_ctx_a->streams[audioindex_a]->time_base) <= 0){
			ifmt_ctx=ifmt_ctx_v;
			stream_index=videoindex_out;

			if(av_read_frame(ifmt_ctx, &pkt) >= 0){
				do{
					if(pkt.stream_index==videoindex_v){
						cur_pts_v=pkt.pts;
						break;
					}
				}while(av_read_frame(ifmt_ctx, &pkt) >= 0);
			}else{
				break;
			}
		}else{
			ifmt_ctx=ifmt_ctx_a;
			stream_index=audioindex_out;
			if(av_read_frame(ifmt_ctx, &pkt) >= 0){
				do{
					if(pkt.stream_index==audioindex_a){
						cur_pts_a=pkt.pts;
						break;
					}
				}while(av_read_frame(ifmt_ctx, &pkt) >= 0);
			}else{
				break;
			}

		}

		in_stream  = ifmt_ctx->streams[pkt.stream_index];
		out_stream = ofmt_ctx->streams[stream_index];
//FIX
#if USE_H264BSF
		av_bitstream_filter_filter(h264bsfc, in_stream->codec, NULL, &pkt.data, &pkt.size, pkt.data, pkt.size, 0);
#endif
#if USE_AACBSF
		av_bitstream_filter_filter(aacbsfc, in_stream->codec, NULL, &pkt.data, &pkt.size, pkt.data, pkt.size, 0);
#endif
		//FIX：No PTS (Example: Raw H.264)
		//Simple Write PTS
		if(pkt.pts==AV_NOPTS_VALUE){
			//Write PTS
			AVRational time_base1=in_stream->time_base;
			//Duration between 2 frames (us)
			int64_t calc_duration=(double)AV_TIME_BASE/av_q2d(in_stream->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);
			frame_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;
		pkt.stream_index=stream_index;

		printf("Write 1 Packet. size:%5d\tpts:%8d\n",pkt.size,pkt.pts);
		//写入（Write）
		if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0) {
			printf( "Error muxing packet\n");
			break;
		}
		av_free_packet(&pkt);

	}
	//写文件尾（Write file trailer）
	av_write_trailer(ofmt_ctx);

#if USE_H264BSF
	av_bitstream_filter_close(h264bsfc);
#endif
#if USE_AACBSF
	av_bitstream_filter_close(aacbsfc);
#endif

end:
	avformat_close_input(&ifmt_ctx_v);
	avformat_close_input(&ifmt_ctx_a);
	/* 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;
}

结果

音频：huoyuanjia.mp3

下载

SourceForge项目主页：

https://sourceforge.net/projects/simplestffmpegformat/

http://download.csdn.net/detail/leixiaohua1020/8005317

最简单的基于FFmpeg的封装格式处理：视音频复用器（muxer）