Question

我正在使用ffmpeg阅读mpeg4视频流。我使用它的一些属性并使用这些属性执行一些过程。我想要的是使用像vlc这样的播放器播放打开的视频。然后我需要在处理后播放输出视频以检查是否存在延迟。是否可以将视频提供给端口。这样我就可以从特定端口将视频作为vlc播放器的输入。

这是我到目前为止的代码。我使用MV_generation方法从中提取特征并从中进行比较。

static int MV_generation(const AVPacket *pkt)
{
    std::vector<unsigned long long> vl = File_read();
    std::hash<string> hash1;
    std::ios_base::app);
    double x_src_val = 0;
    double y_src_val = 0;
    double x_dst_val = 0;
    double y_dst_val = 0;

    int ret = avcodec_send_packet(video_dec_ctx, pkt);
    if (ret < 0) {
        //fprintf(stderr, "Error while sending a packet to the decoder: %s\n", av_err2str(ret));
        return ret;
    }
    video_frame_count++;
    while (ret >= 0){

        ret = avcodec_receive_frame(video_dec_ctx, frame);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        }
        else if (ret < 0) {
            return ret;
        }
        if (ret >= 0) {
            AVFrameSideData *sd;
            sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);

            if (sd) {

                const AVMotionVector *mvs = (const AVMotionVector *)sd->data;

                int size_sd = sd->size;
                //outData << size_sd << endl;

                string str = "", str1, str2, str3, str4;
                for (int i = 0; i < size_sd / sizeof(*mvs); i++) {
                    const AVMotionVector *mv = &mvs[i];

                    int x_src = mv->src_x;
                    int y_src = mv->src_y;
                    int x_dst = mv->dst_x;
                    int y_dst = mv->dst_y;


                    if (x_src != x_dst || y_src != y_dst || x_src > 100 || y_src > 100 || x_dst > 100 || y_dst > 100){
                        str1 = to_string(x_src);
                        str2 = to_string(y_src);
                        str3 = to_string(x_dst);
                        str4 = to_string(y_dst);

                        str = str.append(str1).append(str2).append(str3).append(str4);
                    }
                }

                for (unsigned long long y : vl)
                {
                    // Check if any of the numbers are equal to x
                    if (hash1(str) == y)
                    {
                        cout << "matched frame_no : " << video_frame_count << endl;
                    }
                }
            }
            av_frame_unref(frame);
        }
    }
    outData.close();
    return 0;
}

Answer 1

我已经像这样使用opencv显示了帧。

Mat YUV420ToBGRA(uchar *_buffer[3], int _rowBytes, int _width, int _height){

    Mat result(_height, _width, CV_8UC4);
    if (_buffer == NULL || _buffer[0] == NULL || _buffer[1] == NULL || _buffer[2] == NULL)
        return result;

uchar y, cb, cr;

uchar *output = new uchar[_width * _height * 4];
result.data = output;
uchar r, g, b;

for (int i = 0; i < _height; i++){

    for (int j = 0; j < _width; j++){

        y = _buffer[0][(i * _rowBytes) + j];
        cb = _buffer[1][((i / 2)*(_rowBytes / 2)) + (j / 2)];
        cr = _buffer[2][((i / 2)*(_rowBytes / 2)) + (j / 2)];

        b = saturate_cast<uchar>(y + 1.772*(cb - 128));
        g = saturate_cast<uchar>(y - 0.344*(cb - 128) - 0.714*(cr - 128));
        r = saturate_cast<uchar>(y + 1.402*(cr - 128));

        *output++ = b;
        *output++ = g;
        *output++ = r;
        *output++ = 255;
    }
}

imshow("video", result);
waitKey(10);
return result;
}

在main方法中我像这样调用这个方法。

static AVFrame *frame = NULL;
YUV420ToBGRA(frame->data,
        frame->linesize[0],
        frame->width,
        frame->height);

请注意，您必须在循环内调用此方法，该循环逐帧输入方法。

Answer 2

一旦帧转换为mat

，也可以使用此方法

int ShowVideo(Mat mRGB, string textOnVideo, string windowName){
    namedWindow(windowName, 1);


Pict_type = frame->pict_type;
//cout << av_get_picture_type_char(Pict_type); //I P or B frame 

if (AV_PICTURE_TYPE_NONE != Pict_type)
{
    namedWindow(windowName, 1);
    mRGB = Mat(dec_ctx->height, dec_ctx->width, CV_8UC3);
    Mat mYUV(dec_ctx->height + dec_ctx->height / 2, dec_ctx->width, CV_8UC1, (void*)buff);
    cvtColor(mYUV, mRGB, CV_YUV2RGB_YV12, 3);

    putText(mRGB, textOnVideo,
        Point(100, 100), FONT_HERSHEY_PLAIN, 1, Scalar(0, 0, 255, 255));


    imshow(windowName, mRGB);
    waitKey(1);
}
return 0;
}

如何使用ffmpeg输出媒体流？

2 个答案: