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Tue, 16 Dec 2025 16:59:45 +0100 (CET) Message-ID-Hash: WXRBOMSQS7FYEVSCTQIPTGW7ZBPXKS4K X-Message-ID-Hash: WXRBOMSQS7FYEVSCTQIPTGW7ZBPXKS4K X-MailFrom: SRS0=MYhr=6W=phare.normalesup.org=george@ffmpeg.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; header-match-ffmpeg-devel.ffmpeg.org-0; header-match-ffmpeg-devel.ffmpeg.org-1; header-match-ffmpeg-devel.ffmpeg.org-2; header-match-ffmpeg-devel.ffmpeg.org-3; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list Reply-To: FFmpeg development discussions and patches Subject: [FFmpeg-devel] Re: [PATCH] avfilter/avfiltergraph: always retry format negotiation after auto-filters (PR #21100) List-Id: FFmpeg development discussions and patches Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: Nicolas George via ffmpeg-devel Cc: Nicolas George Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Archived-At: List-Archive: List-Post: Niklas Haas via ffmpeg-devel (HE12025-12-04): > >From 60a3b0848e038d75a59dd942c547787c6e68869a Mon Sep 17 00:00:00 2001 > From: Niklas Haas > Date: Thu, 4 Dec 2025 13:25:03 +0100 > Subject: [PATCH 1/2] avfilter/avfiltergraph: always retry format negotiation > after auto-filters > > There is an edge case not covered by the current logic: If there is only > a single auto-filter inserted, but the auto-inserted filter is incompatible > with a *different* format attribute (after settling the previous formats), > we may need a second auto-filter (e.g. `scale`) to settle the newly introduced > incompatibility. I have strong doubts about this and the code it is trying to fix. And since it was pushed too soon without review, I reserve the right to revert, but let us discuss first. The original negotiation code is designed for one single conversion filter that does everything: if it is possible to convert at all, then inserting the right conversion filter for the media type (scale for video, aresample for audio) would be able to make the conversion. This is not theoretical: unlike video, audio had multiple dimensions in the negotiation from the start, and over time multiple subtle adjustments had to be made to avoid doing multiple conversions due to apparent incompatibilities. And it is not a purely technical choice, it is also a choice for user experience: if they want to control finely where the conversion happens, the do not have to also worry about what conversion happens. They can, but they do not have to. But then you added the alpha mode negotiation, and you broke that. So yes, this is not a proper fix. The proper fix would be to make sure scale can convert between straight and premultiplied alpha. Please fix your fix. Regards, -- Nicolas George _______________________________________________ ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org