實戰小項目之ffmpeg推流yolo視頻實時檢測

     以前實現了yolo圖像的在線檢測，此次主要完成遠程視頻的檢測。主要包括推流--収流--檢測顯示三大部分

　　首先說一下推流，主要使用ffmpeg命令進行本地攝像頭的推流，爲了實現首屏秒開使用-g設置gop大小，同時使用-b下降網絡負載，保證流暢度。

linux

ffmpeg -r 30  -i /dev/video0 -vcodec h264 -max_delay 100 -f flv -g 5 -b 700000 rtmp://219.216.87.170/live/test1

 window

ffmpeg -r 30  -f vfwcap -i 0 -vcodec h264 -max_delay 100 -f flv -g 5 -b 700000 rtmp://219.216.87.170/live/test1

 

ffmpeg -list_devices true -f dshow -i dummy  
ffmpeg -r 30  -f dshow -i video="1.3M HD WebCam" -vcodec h264 -max_delay 100 -f flv -g 5 -b 700000 rtmp://219.216.87.170/live/tes
t1

 

　　其次是収流，収流最開始的時候，有很大的延遲，大約5秒，後來經過優化，如今延時保證在1s之內，仍是能夠接收的，直接上収流的程序

AVFormatContext *pFormatCtx;
    int i, videoindex;
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame, *pFrameRGB;
    uint8_t *out_buffer;
    AVPacket *packet;
    //int y_size;
    int ret, got_picture;
    struct SwsContext *img_convert_ctx;
    //輸入文件路徑
//    char filepath[] = "rtmp://219.216.87.170/vod/test.flv";
    char filepath[] = "rtmp://219.216.87.170/live/test1";
    int frame_cnt;

    printf("wait for playing %s\n", filepath);
    av_register_all();
    avformat_network_init();
    pFormatCtx = avformat_alloc_context();
    printf("size %ld\tduration %ld\n", pFormatCtx->probesize,
            pFormatCtx->max_analyze_duration);
    pFormatCtx->probesize = 20000000;
    pFormatCtx->max_analyze_duration = 2000;
//    pFormatCtx->interrupt_callback.callback = timout_callback;
//    pFormatCtx->interrupt_callback.opaque = pFormatCtx;
//    pFormatCtx->flags |= AVFMT_FLAG_NONBLOCK;

    AVDictionary* options = NULL;
    av_dict_set(&options, "fflags", "nobuffer", 0);
//    av_dict_set(&options, "max_delay", "100000", 0);
//    av_dict_set(&options, "rtmp_transport", "tcp", 0);
//    av_dict_set(&options, "stimeout", "6", 0);

    printf("wating for opening file\n");
    if (avformat_open_input(&pFormatCtx, filepath, NULL, &options) != 0) {
        printf("Couldn't open input stream.\n");
        return -1;
    }
    av_dict_free(&options);
    printf("wating for finding stream\n");
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        printf("Couldn't find stream information.\n");
        return -1;
    }
    videoindex = -1;
    for (i = 0; i < pFormatCtx->nb_streams; i++)
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoindex = i;
            break;
        }
    if (videoindex == -1) {
        printf("Didn't find a video stream.\n");
        return -1;
        }

    pCodecCtx = pFormatCtx->streams[videoindex]->codec;
    pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL) {
        printf("Codec not found.\n");
        return -1;
        }
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        printf("Could not open codec.\n");
        return -1;
        }
    /*
     * 在此處添加輸出視頻信息的代碼
     * 取自於pFormatCtx，使用fprintf()
     */
    pFrame = av_frame_alloc();
    pFrameRGB = av_frame_alloc();
    out_buffer = (uint8_t *) av_malloc(
            avpicture_get_size(AV_PIX_FMT_BGR24, pCodecCtx->width,
                    pCodecCtx->height));
    avpicture_fill((AVPicture *) pFrameRGB, out_buffer, AV_PIX_FMT_BGR24,
            pCodecCtx->width, pCodecCtx->height);
    packet = (AVPacket *) av_malloc(sizeof(AVPacket));
    //Output Info-----------------------------
    printf("--------------- File Information ----------------\n");
    av_dump_format(pFormatCtx, 0, filepath, 0);
    printf("-------------------------------------------------\n");
    img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
            pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,
            AV_PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL);
    CvSize imagesize;
    imagesize.width = pCodecCtx->width;
    imagesize.height = pCodecCtx->height;
    IplImage *image = cvCreateImageHeader(imagesize, IPL_DEPTH_8U, 3);
    cvSetData(image, out_buffer, imagesize.width * 3);
    cvNamedWindow(filepath, CV_WINDOW_AUTOSIZE);

    frame_cnt = 0;
    int num = 0;
    while (av_read_frame(pFormatCtx, packet) >= 0) {
        if (packet->stream_index == videoindex) {
            /*
             * 在此處添加輸出H264碼流的代碼
             * 取自於packet，使用fwrite()
             */
            ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture,
                    packet);
            if (ret < 0) {
                printf("Decode Error.\n");
                return -1;
            }
            if (got_picture) {
                sws_scale(img_convert_ctx,
                        (const uint8_t* const *) pFrame->data, pFrame->linesize,
                        0, pCodecCtx->height, pFrameRGB->data,
                        pFrameRGB->linesize);

                printf("Decoded frame index: %d\n", frame_cnt);

                /*
                 * 在此處添加輸出YUV的代碼
                 * 取自於pFrameYUV，使用fwrite()
                 */

                frame_cnt++;
                cvShowImage(filepath, image);
                cvWaitKey(30);

            }
        }
        av_free_packet(packet);
        }

    sws_freeContext(img_convert_ctx);

    av_frame_free(&pFrameRGB);
    av_frame_free(&pFrame);
    avcodec_close(pCodecCtx);
    avformat_close_input(&pFormatCtx);

    return 0;

　　將解壓後的數據區與opencv的IplImage的數據區映射，實現opencv顯示。

　　

　　檢測部分，主要使用IplImage與yolo中的圖像進行對接，在圖像轉換方面，進行了部分優化，縮減一些沒必要要的步驟。而後使用線程區接收ffmepg流，主循環裏區作檢測並顯示。須要作線程同步處理，只有當收到新流時，纔去檢測。