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

int OpenInput(char *fileName)
{context = avformat_alloc_context();context->interrupt_callback.callback = interrupt_cb;AVInputFormat *ifmt = av_find_input_format("dshow");AVDictionary *format_opts =  nullptr;av_dict_set_int(&format_opts, "rtbufsize", 18432000  , 0);int ret = avformat_open_input(&context, fileName, ifmt, &format_opts);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;
}

int InitOutputCodec(AVCodecContext** pOutPutEncContext, int iWidth, int iHeight)
{AVCodec *  pH264Codec = avcodec_find_encoder(AV_CODEC_ID_H264);if(NULL == pH264Codec){printf("%s", "avcodec_find_encoder failed");return  0;}*pOutPutEncContext = avcodec_alloc_context3(pH264Codec);(*pOutPutEncContext)->codec_id = pH264Codec->id;(*pOutPutEncContext)->time_base.num =0;(*pOutPutEncContext)->time_base.den = 1;(*pOutPutEncContext)->pix_fmt            = AV_PIX_FMT_YUV420P;(*pOutPutEncContext)->width              =  iWidth;(*pOutPutEncContext)->height             = iHeight;(*pOutPutEncContext)->has_b_frames = 0;(*pOutPutEncContext)->max_b_frames = 0;AVDictionary *options = nullptr;(*pOutPutEncContext)->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;int ret = avcodec_open2(*pOutPutEncContext, pH264Codec, &options);if (ret < 0){printf("%s", "open codec failed");return  ret;}return 1;
}

int OpenOutput(char *fileName)
{int ret = 0;ret  = avformat_alloc_output_context2(&outputContext, nullptr, "flv", fileName);if(ret < 0){goto Error;}ret = avio_open2(&outputContext->pb, fileName, AVIO_FLAG_READ_WRITE,nullptr, nullptr);  if(ret < 0){goto Error;}for(int i = 0; i < context->nb_streams; i++){AVStream * stream = avformat_new_stream(outputContext, pOutPutEncContext->codec);stream->codec = pOutPutEncContext;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 ;
}

std::shared_ptr<AVPacket> ReadPacketFromSource()
{std::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());lastFrameRealtime = av_gettime();int ret = av_read_frame(context, packet.get());if(ret >= 0){return packet;}else{return nullptr;}
}

int YUV422To420(uint8_t *yuv422, uint8_t *yuv420, int width, int height)
{int s = width * height;int i,j,k = 0;for(i = 0; i < s;i++){yuv420[i] = yuv422[i * 2];}for(i = 0; i < height; i++){if(i%2 != 0) continue;for(j = 0; j <(width /2); j++){if(4 * j + 1 > 2 * width) break;yuv420[s + k * 2 * width / 4 +j] = yuv422[i * 2 * width + 4 *j + 1];}k++;}k = 0;for(i = 0; i < height; i++){if(i % 2 == 0) continue;for(j = 0; j < width / 2; j++){if(4 * j + 3 > 2 * width) break;yuv420[s + s / 4 + k * 2 *width / 4 + j] = yuv422[i *2 * width + 4 * j + 3];}k++;}return 1;
};

 string fileInput="video=Integrated Webcam";string fileOutput="rtmp://127.0.0.1/live/mystream";Init();if(OpenInput((char *)fileInput.c_str()) < 0){cout << "Open file Input failed!" << endl;this_thread::sleep_for(chrono::seconds(10));return 0;}InitOutputCodec(&pOutPutEncContext,DstWidth,DstHeight);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];int iGetPic = 0;uint8_t *yuv420Buffer = (uint8_t *)malloc(DstWidth * DstHeight * 3 / 2);yuv420Buffer[DstWidth * DstHeight * 3 / 2 - 1] = 0;while(true){auto packet = ReadPacketFromSource();if(packet){auto pSwsFrame = av_frame_alloc();int numBytes=av_image_get_buffer_size(AV_PIX_FMT_YUYV422, DstWidth, DstHeight, 1);YUV422To420(packet->data, yuv420Buffer, DstWidth, DstHeight);av_image_fill_arrays((pSwsFrame)->data, (pSwsFrame)->linesize, yuv420Buffer, AV_PIX_FMT_YUV420P, DstWidth, DstHeight, 1);AVPacket *pTmpPkt = (AVPacket *)av_malloc(sizeof(AVPacket));av_init_packet(pTmpPkt);pTmpPkt->data = NULL;pTmpPkt->size = 0;int iRet = avcodec_encode_video2(pOutPutEncContext, pTmpPkt, pSwsFrame, &iGetPic);if(iRet >= 0 && iGetPic){int ret = av_write_frame(outputContext, pTmpPkt);cout << "ret:"<< ret <<endl;//this_thread::sleep_for(std::chrono::milliseconds(40));}av_frame_free(&pSwsFrame);av_packet_free(&pTmpPkt);}}CloseInput();CloseOutput();cout <<"Transcode file end!" << endl;this_thread::sleep_for(chrono::hours(10));return 0;