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From: Jerome Martinez <jerome@mediaarea.net>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 3/3] [RFC] avcodec/ffv1: Better rounding for slice positions
Date: Sat, 7 Oct 2023 06:52:07 +0200
Message-ID: <63f89695-1a25-41fa-900d-650e4da6f43f@mediaarea.net> (raw)
In-Reply-To: <20231007001444.31861-3-michael@niedermayer.cc>

On 07/10/2023 02:14, Michael Niedermayer wrote:
> This fixes green lines in some odd dimensions with some slice configurations
> like Ticket 5548
>
> This also changes the encoder and whats encoded, and would require an
> update to the specification. This change attempts to limit the change
> to configurations that have missing lines currently.

It changes a lot the count of pixels per slice, and , e.g. with 4:2:2 and 4 slices per direction (16 slices in total), 13 pixel width:
before: 3/3/3/4 for luma, 2/2/2/2 for chroma (so 1 chroma too much)
after: 4/4/2/3 for luma, 2/2/1/2 for chroma

Wouldn't it easier for spec and maths to keep the previous behavior for luma and consider extra chroma as to be not encoded?
Something like 3/3/3/4 for luma, 2/2/2/1 for chroma
Actually maybe not really a change for spec in that case, more making a part more explicit while considering the patch as a bug fix rather than a spec change.

Or did I miss another issue? I'll check more a bit later.

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  reply	other threads:[~2023-10-07  4:52 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-07  0:14 [FFmpeg-devel] [PATCH 1/3] avcodec/ffv1enc: Slice combination is unsupported Michael Niedermayer
2023-10-07  0:14 ` [FFmpeg-devel] [PATCH 2/3] avcodec/ffv1: Store and reuse sx/sy Michael Niedermayer
2023-10-07  0:14 ` [FFmpeg-devel] [PATCH 3/3] [RFC] avcodec/ffv1: Better rounding for slice positions Michael Niedermayer
2023-10-07  4:52   ` Jerome Martinez [this message]
2023-10-07 17:11     ` Michael Niedermayer

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