[Libav-user] The issue of generating YUV422 image from RGB48

[Paul B Mahol]

On 5/11/16, Hao Yang <hao at multicorewareinc.com> wrote:
> I want to use ffmpeg to convert image from RGB48 into YUV422, then generate
> mp4 file finally.
>
> But I found that conversion result shows the color of YUV422 image is not
> same as RGB48. I also tried to convert image from RGB24 (just convert from

If its not same, what is it?

> RGB48) into YUV422, no issue found.
>
>
> Do anyone know is this the bug in ffmpeg for such conversion or some
> mistake in my code?
>
> Thanks so much in advance!!
>
>
>
> The following code is from my project and used to conversion:
>
>
> void conversion()
>
> {
>
> //xxxxxxxx;
>
>
>
> rgb_pixel_format = AV_PIX_FMT_RGB48BE;
>
> pCodecCtx->pix_fmt = yuv_pixel_format = AV_PIX_FMT_YUV422P;
>
> scale_flag = SWS_POINT;
>
>
>
> //xxxxxxxx;
>
>
>
>     size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width,
> pCodecCtx->height);
>
>     yuv_buff = (unsigned char*)av_malloc(size);
>
>
>
>     pSwsCtx=
> sws_getContext(pCodecCtx->width,pCodecCtx->height,rgb_pixel_format,
>
>
> pCodecCtx->width,pCodecCtx->height,yuv_pixel_format,scale_flag,NULL,NULL,NULL);
>
>
>
>
>
>
>     for (file_index = 0; file_index < image_num; file_index ++)
>
>     {
>
>         rgb_buff = (unsigned char*)av_malloc(image_data->length);
>
>         memcpy(rgb_buff, image_data->data, image_data->length);
>
>
>
>         avpicture_fill((AVPicture*)pRGBFrame, (unsigned char*)rgb_buff,
> rgb_pixel_format, nWidth, nHeight);
>
>
>
>         avpicture_fill((AVPicture*)pFrame, (unsigned char*)yuv_buff,
> yuv_pixel_format, nWidth, nHeight);
>
>
>
>         //rotate RGB image
>
>         pRGBFrame->data[0]  += pRGBFrame->linesize[0] * (nHeight - 1);
>
>         pRGBFrame->linesize[0] *= -1;
>
>         pRGBFrame->data[1]  += pRGBFrame->linesize[1] * (nHeight / 2 - 1);
>
>
>         pRGBFrame->linesize[1] *= -1;
>
>         pRGBFrame->data[2]  += pRGBFrame->linesize[2] * (nHeight / 2 - 1);
>
>
>         pRGBFrame->linesize[2] *= -1;
>
>
>
>         //covert RGB into YUV
>
>
> sws_scale(pSwsCtx,pRGBFrame->data,pRGBFrame->linesize,0,pCodecCtx->height,pFrame->data,pFrame->linesize);
>
>
>             yuv_file = fopen(yuv_rst_file[file_index], "wb");
>
>
>
>             fseek(yuv_file, 0L, SEEK_END);
>
>             rewind(yuv_file);
>
>
> fwrite(pFrame->data[0],(pCodecCtx->width)*(pCodecCtx->height),1,yuv_file);
>
>
>
> fwrite(pFrame->data[1],(pCodecCtx->width)*(pCodecCtx->height)/2,1,yuv_file);
>
>
>
> fwrite(pFrame->data[2],(pCodecCtx->width)*(pCodecCtx->height)/2,1,yuv_file);
>
>
>             fclose(yuv_file);
>
>         }
>
> }
>