關於使用智能指針對降低ffmpeg延時的測試

這是使用智能指針的代碼，轉發rtspliu流用vlc播放，延時幾乎沒有

#include "stdafx.h"
#include "pch.h"
#include <string>
#include <memory>
#include <thread>
#include <iostream>
using namespace std;

AVFormatContext *inputContext = nullptr;
AVFormatContext *inputContext2 = nullptr;
AVFormatContext * outputContext;
int OpenInput(string inputUrl)
{
	 inputContext = avformat_alloc_context();	
	 AVDictionary* options = nullptr; 
	 av_dict_set(&options, "rtsp_transport", "tcp", 0);
	 int ret = avformat_open_input(&inputContext, inputUrl.c_str(), nullptr,&options);
	 if(ret < 0)
	{
		av_log(NULL, AV_LOG_ERROR, "Input file open input failed\n");
		return  ret;
	}
	ret = avformat_find_stream_info(inputContext,nullptr);
	if(ret < 0)
	{
		avformat_close_input(&inputContext);
		av_log(NULL, AV_LOG_ERROR, "Find input file stream inform failed\n");
	}

	return ret;
}

int OpenInput2(string inputUrl)
{
	 inputContext2 = avformat_alloc_context();	
	 AVDictionary* options = nullptr; 
	 av_dict_set(&options, "rtsp_transport", "udp", 0);
	 int ret = avformat_open_input(&inputContext2, inputUrl.c_str(), nullptr,&options);
	 if(ret < 0)
	{
		av_log(NULL, AV_LOG_ERROR, "Input file open input failed\n");
		return  ret;
	}
	ret = avformat_find_stream_info(inputContext2,nullptr);
	if(ret < 0)
	{
		avformat_close_input(&inputContext2);
		av_log(NULL, AV_LOG_ERROR, "Find input file stream inform failed\n");
	}
	return ret;
}
shared_ptr<AVPacket> ReadPacketFromSource()
{
	shared_ptr<AVPacket> packet(static_cast<AVPacket*>(av_malloc(sizeof(AVPacket))), [&](AVPacket *p) { av_packet_free(&p); av_freep(&p);});
	av_init_packet(packet.get());
	int ret = av_read_frame(inputContext, packet.get());
	if(ret >= 0)
	{
		return packet;
	}
	else
	{
		return nullptr;
	}
}

shared_ptr<AVPacket> ReadPacketFromSource2()
{
	shared_ptr<AVPacket> packet(static_cast<AVPacket*>(av_malloc(sizeof(AVPacket))), [&](AVPacket *p) { av_packet_free(&p); av_freep(&p);});
	av_init_packet(packet.get());
	int ret = av_read_frame(inputContext2, packet.get());
	if(ret >= 0)
	{
		return packet;
	}
	else
	{
		return nullptr;
	}
}
void av_packet_rescale_ts(AVPacket *pkt, AVRational src_tb, AVRational dst_tb)
{
	if (pkt->pts != AV_NOPTS_VALUE)
		pkt->pts = av_rescale_q(pkt->pts, src_tb, dst_tb);
	if (pkt->dts != AV_NOPTS_VALUE)
		pkt->dts = av_rescale_q(pkt->dts, src_tb, dst_tb);
	if (pkt->duration > 0)
		pkt->duration = av_rescale_q(pkt->duration, src_tb, dst_tb);
}
int WritePacket(shared_ptr<AVPacket> packet)
{
	auto inputStream = inputContext->streams[packet->stream_index];
	auto outputStream = outputContext->streams[packet->stream_index];				
	av_packet_rescale_ts(packet.get(),inputStream->time_base,outputStream->time_base);
	return av_interleaved_write_frame(outputContext, packet.get());
}

int OpenOutput(string outUrl)
{
	
	int ret  = avformat_alloc_output_context2(&outputContext, nullptr, "rtsp", outUrl.c_str());
	if(ret < 0)
	{
		av_log(NULL, AV_LOG_ERROR, "open output context failed\n");
		avformat_close_input(&inputContext);
		return -1;
	}
	if (!(outputContext->oformat->flags & AVFMT_NOFILE)) {
		ret = avio_open2(&outputContext->pb, outUrl.c_str(), AVIO_FLAG_READ_WRITE, nullptr, nullptr);
		if (ret < 0)
		{
			av_log(NULL, AV_LOG_ERROR, "open avio failed");
			avformat_close_input(&inputContext);
			avformat_close_input(&outputContext);
			return -1;
		}
	}


	for(int i = 0; i < inputContext->nb_streams; i++)
	{
		AVStream * stream = avformat_new_stream(outputContext, inputContext->streams[i]->codec->codec);				
		ret = avcodec_copy_context(stream->codec, inputContext->streams[i]->codec);	
		if(ret < 0)
		{
			av_log(NULL, AV_LOG_ERROR, "copy coddec context failed");
			avformat_close_input(&inputContext);
			avformat_close_input(&outputContext);
			return -1;
		}
	}

	ret = avformat_write_header(outputContext, nullptr);
	if(ret < 0)
	{
		av_log(NULL, AV_LOG_ERROR, "format write header failed");
		avformat_close_input(&inputContext);
		for (int i = 0; i < outputContext->nb_streams; i++)
		{
			avcodec_close(outputContext->streams[i]->codec);
		}
		avformat_close_input(&outputContext);
		return -1;
	}

	av_log(NULL, AV_LOG_FATAL, " Open output file success %s\n",outUrl.c_str());			
	return ret ;

}

void Init()
{
	av_register_all();
    avfilter_register_all();
	avformat_network_init();
	avcodec_register_all();
	av_log_set_level(AV_LOG_ERROR);
}
int _tmain(int argc, _TCHAR* argv[])
{
	Init();
	string input = "rtsp://admin:[email protected]/stream0";
	string output = "rtsp://192.168.31.181:9990/test";
	int ret = OpenInput(input);
	if(ret >= 0)
	{
		ret = OpenOutput(output);
	}
	while(true)
	{
		shared_ptr<AVPacket> packet = nullptr;
		packet = ReadPacketFromSource();
		if(packet)
		{
			WritePacket(packet);
		}
	}
	return 0;
}

下面是使用指針的部分代碼做法(與上面代碼僅僅是這裏不同而已)，有3~4秒延時

	while (1) {
		av_read_frame(infmt_ctx, &packet);
		if (packet.stream_index == stream_index) {

			av_interleaved_write_frame(outfmt_ctx, &outpkt);
			av_free_packet(&outpkt);

		}
		av_packet_unref(&packet);
	}