sws_scale解出来的RGB图像颠倒问题

sws_scale解出来的RGB图像颠倒问题

转载自: http://blog.csdn.net/rightorwrong/article/details/6432042

AVFrame *  pFrame;                    //  Frame 
AVCodecContext *  pContext;           //  Codec Context
int  nUsedBytes  =  avcodec_decode_video(pContext, pFrame,   & nFrame, pSrcBuffer, nSrcLength);
if (nUsedBytes  >   0 )
{
    AVFrame  out_pic;
    SwsContext* img_convert_ctx = sws_getContext(pContext->width, pContext->height, pContext->pix_fmt, nDestW, nDestH,(PixelFormat)PIX_FMT_BGR24,SWS_BICUBIC, NULL, NULL, NULL);
    if(img_convert_ctx != NULL)
    {
        if(avpicture_alloc((AVPicture *)&out_pic, PIX_FMT_RGB24, nDestW, nDestH)>=0)
        {
            pFrame->data[0] = pFrame->data[0]+pFrame->linesize[0]*(pContext->height-1);
            pFrame->data[1] = pFrame->data[1]+pFrame->linesize[0]*pContext->height/4-1;
       pFrame->data[2] = pFrame->data[2]+pFrame->linesize[0]*pContext->height/4-1;
            pFrame->linesize[0] *= -1;
            pFrame->linesize[1] *= -1;
       pFrame->linesize[2] *= -1;
       sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pContext->height, out_pic.data, out_pic.linesize);
            avpicture_free((AVPicture *)&out_pic);
        }
        sws_freeContext(img_convert_ctx);
    }
}

AVFrame的data和linesize：

YUV: linesize[0] =  width + padding size(16+16),linesize[1]=linesize[0]/2

        data[0],data[1],data[2]分别代表yuv 

RGB: linesize[0] = width*pixel_size  for RGB
        data[0]为packet rgb

  pFrame->data[0] = pFrame->data[0]+pFrame->linesize[0]*(pContext->height-1);
  pFrame->data[1] = pFrame->data[1]+pFrame->linesize[1]*(pContext->height/2-1);
  pFrame->data[2] = pFrame->data[2]+pFrame->linesize[2]*(pContext->height/2-1);