ffmpeg 发布hls流

     本来主要讲述如何利用ffmpeg将输入视频流通过转码的方式转成m3u8文件。如何通过http的方法将切边推送给客户端,不在本文中讲述。

输入视频流可以是rtsp流，也可以是http，还可以是文件等等。转码的基本流程如下图所示:

图1. 生产hls视频流

视频流解复用可以获得packet,对应的实现方法是av_read_frame。 

       下面给出代码：

   1. 初始化ffmpeg

void Init()
{
      av_register_all();
      avfilter_register_all();
      avformat_network_init();
      av_log_set_level(AV_LOG_ERROR);
}

　初始化ffmepg是必须的，否则调用相关的ffmpeg会返回错误。

2. 打开视频流

  

int OpenInput(char *fileName)
{
	 context = avformat_alloc_context();
	 context->interrupt_callback.callback = interrupt_cb;
	int ret = avformat_open_input(&context, fileName, nullptr,nullptr);
	if(ret < 0)
	{
		return  ret;
	}
	ret = avformat_find_stream_info(context,nullptr);
	av_dump_format(context, 0, fileName, 0);
	if(ret >= 0) 
	{
		cout <<"open input stream successfully" << endl;
	}
	return ret;
}

　3.创建hls输出上下文

int OpenOutput(char *fileName)
{
    int ret = 0;
     ret  = avformat_alloc_output_context2(&outputContext, nullptr, "hls", fileName);
    if(ret < 0)
    {
        goto Error;
    }
    ret = avio_open2(&outputContext->pb, fileName, AVIO_FLAG_READ_WRITE,nullptr, nullptr);    
    if(ret < 0)
    {
        goto Error;
    }

    av_opt_set(outputContext->priv_data, "hls_time" ,"5" , AV_OPT_SEARCH_CHILDREN);
    //av_opt_set(outputContext->priv_data, "hls_list_size" ,"10" , AV_OPT_SEARCH_CHILDREN);
    av_opt_set(outputContext->priv_data, "hls_wrap" ,"5" , AV_OPT_SEARCH_CHILDREN);

    for(int i = 0; i < context->nb_streams; i++)
    {
        AVStream * stream = avformat_new_stream(outputContext, context->streams[i]->codec->codec);
        ret = avcodec_copy_context(stream->codec, context->streams[i]->codec);
        //stream->codec->codec_tag = 0;
        //stream->index = 0;
        if(ret < 0)
        {
            goto Error;
        }
    }
     av_dump_format(outputContext, 0, fileName, 1);
     ret = avformat_write_header(outputContext, nullptr);
    if(ret < 0)
    {
        goto Error;
    }
    if(ret >= 0)
    cout <<"open output stream successfully" << endl;
    return ret ;
Error:
    if(outputContext)
    {
        for(int i = 0; i < outputContext->nb_streams; i++)
        {
            avcodec_close(outputContext->streams[i]->codec);
        }
        avformat_close_input(&outputContext);
    }
    return ret ;
}

 4.解复用

    

AVPacket *ReadPacketFromSource()
{
	std::shared_ptr<AVPacket> packet(static_cast<AVPacket*>(av_malloc(sizeof(AVPacket))), [&](AVPacket *p) { av_free_packet(p); av_freep(&p); });
	av_init_packet(packet.get());
	lastFrameRealtime = av_gettime();
	int ret = av_read_frame(context, packet.get());
	if(ret >= 0)
	{
		return packet.get();
	}
	else
	{
		return nullptr;
	}
}

　av_read_frame返回packet,packet是经过解复用得到的裸码流.

5. 写packet到输出context　

av_write_frame(outputContext, packet);

　demo

int _tmain(int argc, _TCHAR* argv[])
{
	string fileInput= "D:\record\langxi\langxi.ts";
	string fileOutput="D:\test\file\live\wgg2\test.m3u8";
	Init();
	if(OpenInput((char *)fileInput.c_str()) < 0)
	{
		cout << "Open file Input failed!" << endl;
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}
	if(OpenOutput((char *)fileOutput.c_str()) < 0)
	{
		cout << "Open file Output failed!" << endl;
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}
	auto timebase = av_q2d(context->streams[0]->time_base);
	int count = 0;
	auto in_stream = context->streams[0];
	auto out_stream = outputContext->streams[0];
	while(true)
	{
		AVPacket *packet = ReadPacketFromSource();
		if(packet)
		{
		　　　packet->pts = av_rescale_q_rnd(packet->pts, in_stream->time_base, out_stream->time_base, 
　　　　　　　　　　　　 AVRounding(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
        　　　　　　　　packet->dts = av_rescale_q_rnd(packet->dts, in_stream->time_base, out_stream->time_base, AVRounding(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
        　　　　　　　　packet->duration = av_rescale_q(packet->duration, in_stream->time_base, out_stream->time_base);
        　　　　　　　　packet->pos = -1;
		　　　int ret = av_write_frame(outputContext, packet);
		}
		else
		{
			cout <<"write packet end!"<< endl;
			break;
		}
	}
	CloseInput();
	CloseOutput();
	cout <<"Transcode file end!" << endl;
	this_thread::sleep_for(chrono::hours(10));
	return 0;
}

　　如有问题,加群流媒体/Ffmpeg/音视频 127903734交流,群里有demo源码.

视频下载地址：http://www.chungen90.com/?news_3/

 Demo下载地址： http://www.chungen90.com/?news_2