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

[Hao Yang]

This is part of original file:
[image: 内嵌图片 1]

2016-05-11 17:03 GMT+08:00 Paul B Mahol <onemda at gmail.com>:

> 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);
> >
> >         }
> >
> > }
> >
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>
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