Re: [FFmpeg-devel] [PATCH 1/2] avcodec/vvc/refs: fix negative pps_scaling_win offsets

From: Frank Plowman <post@frankplowman.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 1/2] avcodec/vvc/refs: fix negative pps_scaling_win offsets
Date: Mon, 3 Feb 2025 08:05:19 +0000
Message-ID: <eb651de2-b66c-4e74-8dc2-3421ebac177a@frankplowman.com> (raw)
In-Reply-To: <20250202211721.1469377-1-michael@niedermayer.cc>

On 02/02/2025 21:17, Michael Niedermayer wrote:
> The spec seems to allow these to  be negative
> 
> Fixes: left shift of negative value -15
> Fixes: 392687035/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VVC_fuzzer-6559804532785152
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/vvc/refs.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/vvc/refs.c b/libavcodec/vvc/refs.c
> index 8d4b7bb35b2..486515d06db 100644
> --- a/libavcodec/vvc/refs.c
> +++ b/libavcodec/vvc/refs.c
> @@ -147,10 +147,10 @@ static VVCFrame *alloc_frame(VVCContext *s, VVCFrameContext *fc)
>          for (int j = 0; j < frame->ctb_count; j++)
>              frame->rpl_tab[j] = frame->rpl;
>  
> -        win->left_offset   = pps->r->pps_scaling_win_left_offset   << sps->hshift[CHROMA];
> -        win->right_offset  = pps->r->pps_scaling_win_right_offset  << sps->hshift[CHROMA];
> -        win->top_offset    = pps->r->pps_scaling_win_top_offset    << sps->vshift[CHROMA];
> -        win->bottom_offset = pps->r->pps_scaling_win_bottom_offset << sps->vshift[CHROMA];
> +        win->left_offset   = pps->r->pps_scaling_win_left_offset   * (1 << sps->hshift[CHROMA]);
> +        win->right_offset  = pps->r->pps_scaling_win_right_offset  * (1 << sps->hshift[CHROMA]);
> +        win->top_offset    = pps->r->pps_scaling_win_top_offset    * (1 << sps->vshift[CHROMA]);
> +        win->bottom_offset = pps->r->pps_scaling_win_bottom_offset * (1 << sps->vshift[CHROMA]);
>          frame->ref_width   = pps->r->pps_pic_width_in_luma_samples  - win->left_offset   - win->right_offset;
>          frame->ref_height  = pps->r->pps_pic_height_in_luma_samples - win->bottom_offset - win->top_offset;
>  

This patch LGTM.

-- 
Frank

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