CODEWITHSUNDEEP
c++opencvffmpegencodemat
user2789801
user2789801

Reputation: 65

Process AVFrame using opencv mat causing encoding error

I'm trying to decode a video file using ffmpeg, grab the AVFrame object, convert it to opencv mat object, do some processing then convert it back to AVFrame object and encode it back to a video file.

Well, the program can run, but it produces bad result.

I Keep getting errors like "top block unavailable for requested intra mode at 7 19", "error while decoding MB 7 19, bytestream 358", "concealing 294 DC, 294AC, 294 MV errors in P frame" etc.

And the result video got glithes all over it. like this, enter image description here

I'm guessing it's because my AVFrame to Mat and Mat to AVFrame methods, and here they are

//unspecified function
temp_rgb_frame = avcodec_alloc_frame(); 
int numBytes = avpicture_get_size(PIX_FMT_RGB24, width, height); 
uint8_t * frame2_buffer = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t)); 
avpicture_fill((AVPicture*)temp_rgb_frame, frame2_buffer, PIX_FMT_RGB24, width, height);

void CoreProcessor::Mat2AVFrame(cv::Mat **input, AVFrame *output)
{
    //create a AVPicture frame from the opencv Mat input image
    avpicture_fill((AVPicture *)temp_rgb_frame,
        (uint8_t *)(*input)->data,
        AV_PIX_FMT_RGB24,
        (*input)->cols,
        (*input)->rows);

    //convert the frame to the color space and pixel format specified in the sws context

    sws_scale(
        rgb_to_yuv_context, 
        temp_rgb_frame->data,
        temp_rgb_frame->linesize,
        0, height, 
        ((AVPicture *)output)->data, 
        ((AVPicture *)output)->linesize);

    (*input)->release();

}

void CoreProcessor::AVFrame2Mat(AVFrame *pFrame, cv::Mat **mat)
{
    sws_scale(
        yuv_to_rgb_context, 
        ((AVPicture*)pFrame)->data, 
        ((AVPicture*)pFrame)->linesize, 
        0, height, 
        ((AVPicture *)temp_rgb_frame)->data,
        ((AVPicture *)temp_rgb_frame)->linesize);

    *mat = new cv::Mat(pFrame->height, pFrame->width, CV_8UC3, temp_rgb_frame->data[0]);
}

void CoreProcessor::process_frame(AVFrame *pFrame)
{
    cv::Mat *mat = NULL;
    AVFrame2Mat(pFrame, &mat);
    Mat2AVFrame(&mat, pFrame);
}

Am I doing something wrong with the memory? Because if I remove the processing part, just decode and then encode the frame, the result is correct.

Upvotes: 1

Views: 1918

Answers (1)

user2789801
user2789801

Reputation: 65

Well, it turns out I made a mistake at the initialization of temp_rgb_frame,if should be like this,

temp_rgb_frame = avcodec_alloc_frame();
int numBytes = avpicture_get_size(PIX_FMT_RGB24, width, height);
uint8_t * frame2_buffer = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t));
avpicture_fill((AVPicture*)temp_rgb_frame, frame2_buffer, PIX_FMT_RGB24, width, height);

Upvotes: 1

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