改demo程序，调用ffmpeg API，获取rtsp的音视频流，打印每一包的ts，验证是否同步。

运行环境是linux

//FFDecoder.h

#pragma once  

//#define __STDC_CONSTANT_MACROS

extern "C" {  
#include "libavcodec/avcodec.h"  
#include "libavformat/avformat.h"  
#include "libavutil/avutil.h"   
#include "libavutil/opt.h"  
#include "libswscale/swscale.h"  
}  

#pragma comment(lib,"avutil.lib")  
#pragma comment(lib,"avformat.lib")  
#pragma comment(lib,"swresample.lib")  
#pragma comment(lib,"avcodec.lib")  
#pragma comment(lib,"swscale.lib")  


class CFFDecoder  
{  
public:  
	CFFDecoder();  
	virtual ~CFFDecoder();  

	int                 OpenFile(const char *pFilePath);  
	int                 GetMediaInfo(int &nFrameW,int &nFrameH);  
	int                 GetOneFrame(AVFrame *pFrame);  

private:  
	AVFormatContext     *m_pFormatCxt; 

	AVCodecContext      *m_pCodecCtx;  
	AVCodec             *m_pCodec;  

	AVCodecContext      *m_pACodecCtx;  
	AVCodec             *m_pACodec;  

	AVPacket            m_Packet;  
	int                 m_nVideoIndex;  
	int                 m_nAudioIndex;  

	double				m_nLastAudioPTS;
	double				m_nLastVideoPTS;
	double				m_nStartAudioTS;
	double				m_nStartVideoTS;
};  

//FFDecoder.cpp
#include "FFDecoder.h"  

CFFDecoder::CFFDecoder()  
{  
	m_pFormatCxt = avformat_alloc_context();  
	m_pCodecCtx = NULL;  
	m_pCodec = NULL;  
	m_nVideoIndex = -1;  
	m_nAudioIndex = -1;  
	m_nLastAudioPTS = -1;
	m_nLastVideoPTS = -1;
	m_nStartAudioTS = -1;
	m_nStartVideoTS = -1;
}  

CFFDecoder::~CFFDecoder()  
{  

}  

int CFFDecoder::OpenFile(const char *pFilePath)  
{  
	av_register_all();  

	if(avformat_open_input(&m_pFormatCxt,pFilePath,NULL,NULL)<0)  
	{  
		return -1;  
	}  

	if (avformat_find_stream_info(m_pFormatCxt,NULL)<0)  
	{  
		return -2;  
	}  

	//找到音视频对应的流通道  

	for (int i=0;i<m_pFormatCxt->nb_streams;i++)  
	{  
		if (m_pFormatCxt->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)  
		{  
			m_nVideoIndex = i;  
		}  
		else if (m_pFormatCxt->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)  
		{  
			m_nAudioIndex = i;  
		}  
	}  

	if (m_nVideoIndex == -1)  
	{  
		return -3;  
	}  

	//打开相应的解码器  
	m_pCodecCtx = m_pFormatCxt->streams[m_nVideoIndex]->codec;  
	m_pCodec = avcodec_find_decoder(m_pCodecCtx->codec_id);;  
	if(m_pCodec==NULL){    
		return -4;    
	}  

	if(avcodec_open2(m_pCodecCtx, m_pCodec,NULL)<0){  
		return -5;  
	}  

	//打开相应的解码器  
	m_pACodecCtx = m_pFormatCxt->streams[m_nAudioIndex]->codec;  
	m_pACodec = avcodec_find_decoder(m_pACodecCtx->codec_id);;  
	if(m_pACodec==NULL){    
		return -4;    
	}  

	if(avcodec_open2(m_pACodecCtx, m_pACodec,NULL)<0){  
		return -5;  
	}  
	
	m_nStartVideoTS = m_pFormatCxt->streams[m_nVideoIndex]->start_time;
	m_nStartAudioTS = m_pFormatCxt->streams[m_nAudioIndex]->start_time;

	return 0;  
}  

int CFFDecoder::GetMediaInfo(int &nFrameW,int &nFrameH)  
{  
	if(m_pCodecCtx==NULL)  
		return -1;  

	nFrameW = m_pCodecCtx->width;  
	nFrameH = m_pCodecCtx->height;  
	return 0;  
}  

int CFFDecoder::GetOneFrame(AVFrame *pFrame)  
{  
	if(m_pFormatCxt==NULL)  
		return 0;  

	int nGotPicture=-1;  

	if(av_read_frame(m_pFormatCxt,&m_Packet)>=0)  
	{  
		//判断是否为当前视频流中的包  
		if (m_Packet.stream_index == m_nVideoIndex)  
		{  
			//printf("video pts = %ld  dts=%ld  ---  pts=%ld  dur=%ld\n",
			//	m_Packet.pts,m_Packet.dts,
			//	m_Packet.pts*av_q2d(m_pFormatCxt->streams[m_nVideoIndex]->time_base),
			//	m_Packet.pts-m_nLastVideoPTS);
			double pts = m_Packet.pts/90;
			double dts = m_Packet.dts/90;
			double nDur = pts-m_nLastVideoPTS;
			//m_nStartVideoTS = m_pFormatCxt->streams[m_nVideoIndex]->start_time;

			//long pts2 = m_Packet.pts*av_q2d(m_pFormatCxt->streams[m_nVideoIndex]->time_base);
			printf("video pts = %.02f  dts=%.02f   ---  dur=%.02f\n",
				pts,
				dts,
				nDur);
			
			m_nLastVideoPTS = pts;

			int nLen = avcodec_decode_video2(m_pCodecCtx,pFrame,&nGotPicture,&m_Packet);  
			if (nLen<0)  
			{  
				return 0;  
			}  

			if (nGotPicture)  
			{  
				//成功得到一帧数据  
				//long pts = av_frame_get_best_effort_timestamp(pFrame);
				//printf("after decoder video pts=%ld\n",(pts)/90);
				//m_nLastVideoPTS = (pts)/90;
				return nLen;  
			}  
		}
		else if (m_nAudioIndex == m_Packet.stream_index)
		{
			AVRational tb;
			tb.den = 8000;
			tb.num = 1;

			double pts = (m_Packet.pts)/8;
			double dts = m_Packet.dts/8;
			double nDur = pts-m_nLastAudioPTS;
			//long lpts3 = av_rescale_q(pts,m_pFormatCxt->streams[m_nAudioIndex]->time_base,tb);
			//long pts2 = pts*av_q2d(m_pFormatCxt->streams[m_nAudioIndex]->time_base);
			printf("audio pts = %.02f  dts=%.02f   ---  dur=%.02f\n",
				pts,
				dts,
				nDur);

			m_nLastAudioPTS = pts;
			//av_rescale_q_rnd(m_Packet.pts,  m_pFormatCxt->streams[m_nAudioIndex]->time_base,  m_pFormatCxt->streams[m_nAudioIndex]->time_base, AV_ROUND_NEAR_INF));
			
			int ret = avcodec_decode_audio4(m_pACodecCtx, pFrame, &nGotPicture, &m_Packet);
			if (nGotPicture) {
				//AVRational tb;
				//tb.den = pFrame->sample_rate;
				//tb.num = 1;

				//if (m_nLastAudioPTS != AV_NOPTS_VALUE)
				//	m_nLastAudioPTS = av_rescale_q(pFrame->pts, m_pCodecCtx->time_base, tb);
				//else if (pFrame->pkt_pts != AV_NOPTS_VALUE)
				//	m_nLastAudioPTS = av_rescale_q(pFrame->pkt_pts, av_codec_get_pkt_timebase(m_pCodecCtx), tb);

				//printf("after decoder audio pts=%ld\n",m_nLastAudioPTS);
			}
		}

		printf("v.ts(%.02f) - a.ts(%.02f) = %.02f\n",m_nLastVideoPTS,m_nLastAudioPTS,m_nLastVideoPTS - m_nLastAudioPTS);
		
		/*time_t now;
		struct tm *timenow;
		time(&now);
		timenow = localtime(&now);
		printf(">>>>  now time is %s <<<<\n",asctime(timenow));*/
		
		time_t timer;
		struct tm *t_tm;
		time(&timer);
		t_tm = localtime(&timer);
		printf("now time is %4d-%02d-%02d %02d:%02d:%02d\n",
		t_tm->tm_year+1900,
		t_tm->tm_mon,
		t_tm->tm_mday,
		t_tm->tm_hour,
		t_tm->tm_min,
		t_tm->tm_sec);
		
		//printf("a.ts - v.ts = %d\n",m_nLastAudioPTS - m_nLastVideoPTS);
	}  

        av_free_packet(&m_Packet);
	return 0;  
}  

主函数

// FFmpegTest.cpp : 定义控制台应用程序的入口点。
//
#include "FFDecoder.h"


int main(int argc, char **argv)
{
	if(argc!=2)
	{
		printf("err arg.  exe rtsp://...\n");
		return 0;
	}

	char szRTSPUrl[256]={0};
	strcpy(szRTSPUrl,argv[1]);
	printf("rtsp url = %s\n",szRTSPUrl);
	
	CFFDecoder dec;
	dec.OpenFile(szRTSPUrl); 

	AVFrame *pFrame=av_frame_alloc();  
	while(1)  
	{  
		if(dec.GetOneFrame(pFrame)>0)  
		{  
			 //printf("pts=%lld\n",pFrame->pkt_dts);
		}  
	}  

	system("pause");
	return 0;
}

编译脚本：

g++ -o ffts *.cpp -I/usr/local/include/ -I./ -D__STDC_CONSTANT_MACROS -L/usr/local/lib/ -lavcodec -lavdevice -lavformat -lavfilter -lswscale