From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id 259A5439DB for ; Thu, 4 Aug 2022 15:04:51 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id CC5E968B9DD; Thu, 4 Aug 2022 18:04:48 +0300 (EEST) Received: from relay2-d.mail.gandi.net (relay2-d.mail.gandi.net [217.70.183.194]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id ADBD868B830 for ; Thu, 4 Aug 2022 18:04:42 +0300 (EEST) Received: (Authenticated sender: michael@niedermayer.cc) by mail.gandi.net (Postfix) with ESMTPSA id CBE874000D for ; Thu, 4 Aug 2022 15:04:41 +0000 (UTC) Date: Thu, 4 Aug 2022 17:04:41 +0200 From: Michael Niedermayer To: FFmpeg development discussions and patches Message-ID: <20220804150441.GL2088045@pb2> References: <20220802165421.137563-1-george@nsup.org> <20220804134924.GJ2088045@pb2> MIME-Version: 1.0 In-Reply-To: Subject: Re: [FFmpeg-devel] [PATCH 1/7] lavu/pixfmt: summarize yuv naming conventions X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Type: multipart/mixed; boundary="===============0680371217526767126==" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: --===============0680371217526767126== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="RVLHdg3qhy1T2deX" Content-Disposition: inline --RVLHdg3qhy1T2deX Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Aug 04, 2022 at 03:57:27PM +0200, Nicolas George wrote: > Michael Niedermayer (12022-08-04): > > You seem to describe samples as rectangular areas of constant value IIU= C. > > If you look at the ITU/ISO specs (mpeg2, h264 or others) they are descr= ibed > > by point samples. The desity of samples matches. While the default loca= tions > > do not. > > What you list above are where probably most sane people would place the > > samples. But ISO/ITU, probably because of historic TV standard reasons = and > > interlacing convertion reasons place the chroma samples in a more crook= ed way > > I think either the ascii art should be adapted or the text should clari= fy > > this difference >=20 > I am not sure what exactly you explain. What i meant is what is also in AVChromaLocation The chroma sample locations are shifted from where one would expect >=20 > The picture represents memory cells and how we think of them when we > implement generic functions, for example cropping or drawutils. Do we > need to fix all this code somehow? I suspect several filters are somewhat "wrong" for example hflip fliping 4:1:1 would turn a: *--- into ---* where * is teh chroma sample location, i dont think it updates the chroma sample location metadata nor does it apply some filter to chroma to shift by 3/4 samples. so it looks wrong, one of the 2 is neeed. vf_scale contains some code to handle this but iam not seeing code consider= ing the input and output frames chroma location metadata All this leads to small errors, often probably not vissible when you have one one chroma sample for 4 luma samples you will always have some artifacts on sharp color edges, if the location of the chroma sample is wrong the artifact would be more to one side of a diagonal edge than the other. If the locations are correct it should be more symmetric in theory. thx [...] --=20 Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB No great genius has ever existed without some touch of madness. -- Aristotle --RVLHdg3qhy1T2deX Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABEIAB0WIQSf8hKLFH72cwut8TNhHseHBAsPqwUCYuvgBAAKCRBhHseHBAsP qwMrAJ9nNSQFyWX02cXSULg0bInh+KSs/wCfeJ/Nfw8wFMKeRfuMPdeQyEyCHE4= =s5tw -----END PGP SIGNATURE----- --RVLHdg3qhy1T2deX-- --===============0680371217526767126== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". --===============0680371217526767126==--