Re: [FFmpeg-devel] [PATCH] avcodec/mjpegdec: add support for decoding jpeg rgb file with subsampling

[Leo Izen <leo.izen@gmail.com>]

On 3/25/23 22:13, Wang Chuan wrote:
> Fixes ticket #10190
> 
> Signed-off-by: Wang Chuan <ouchuanm@outlook.com>
> ---
>   libavcodec/mjpegdec.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
> index c833d66c4d..aa58f336d4 100644
> --- a/libavcodec/mjpegdec.c
> +++ b/libavcodec/mjpegdec.c
> @@ -574,6 +574,27 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
>               if (s->bits <= 8) s->avctx->pix_fmt = s->cs_itu601 ? 
> AV_PIX_FMT_YUV444P : AV_PIX_FMT_YUVJ444P;
>               else
>                   goto unk_pixfmt;
> +            if (s->component_id[0] == 'R' && s->component_id[1] == 'G' 
> && s->component_id[2] == 'B') {
> +                if (s->bits <= 8)
> +                    s->avctx->pix_fmt = AV_PIX_FMT_GBRP;
> +                else
> +                    goto unk_pixfmt;
> +                if (pix_fmt_id == 0x22221100) {
> +                    s->upscale_h[0] = s->upscale_v[0] = 0;
> +                    s->upscale_h[1] = s->upscale_v[1] = 1;
> +                    s->upscale_h[2] = s->upscale_v[2] = 0;
> +                } else if (pix_fmt_id == 0x22112200) {
> +                    s->upscale_h[0] = s->upscale_v[0] = 1;
> +                    s->upscale_h[1] = s->upscale_v[1] = 0;
> +                    s->upscale_h[2] = s->upscale_v[2] = 0;
> +                } else if (pix_fmt_id == 0x11222200) {
> +                    s->upscale_h[0] = s->upscale_v[0] = 0;
> +                    s->upscale_h[1] = s->upscale_v[1] = 0;
> +                    s->upscale_h[2] = s->upscale_v[2] = 1;
> +                } else {
> +                    goto unk_pixfmt;
> +                }
> +            }
>               s->avctx->color_range = s->cs_itu601 ? AVCOL_RANGE_MPEG : 
> AVCOL_RANGE_JPEG;
>               break;
>           case 0x11000000:

This doesn't work with progressive JPEGs, which still produce the 
"patches welcome" message.

FWIW I already have a patch on the ML to fix this exact issue.

- Leo Izen (thebombzen)

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