Process AVFrame using opencv mat causing encoding error - c++

Question

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,
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.

Answer 1

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);