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