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 9F6D945CAF for ; Tue, 31 Oct 2023 08:41:03 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id B6FFC68CCF5; Tue, 31 Oct 2023 10:40:52 +0200 (EET) Received: from relay7-d.mail.gandi.net (relay7-d.mail.gandi.net [217.70.183.200]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 3DAF668CCF1 for ; Tue, 31 Oct 2023 10:40:46 +0200 (EET) Received: by mail.gandi.net (Postfix) with ESMTPSA id 6BA0220010 for ; Tue, 31 Oct 2023 08:40:45 +0000 (UTC) Date: Tue, 31 Oct 2023 09:40:44 +0100 From: Michael Niedermayer To: FFmpeg development discussions and patches Message-ID: <20231031084044.GQ3543730@pb2> References: MIME-Version: 1.0 In-Reply-To: X-GND-Sasl: michael@niedermayer.cc Subject: Re: [FFmpeg-devel] [PATCH] avcodec/mpegvideo: Remove spec-incompliant inverse quantisation 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="===============5589440420657574306==" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: --===============5589440420657574306== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="OptwOoxYdd7hlNT8" Content-Disposition: inline --OptwOoxYdd7hlNT8 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Oct 30, 2023 at 02:11:27PM +0100, Andreas Rheinhardt wrote: > Section 7.4.4 of the MPEG-2 specifications requires that the > last bit of the last coefficient be toggled so that the sum > of all coefficients is odd; both our decoder and encoder > did this only if the bitexact flag has been set (although > stuff like this should be behind AV_CODEC_FLAG2_FAST). > This patch changes this by removing the spec-incompliant > functions. This commit message should include benchamarks documenting the speed loss (of the unquantize, the IDCT and overall) It is expected that the speed of some IDCTs will be impacted negativly as the non zero terms will prevent the skiping of some significant code as well as information about how much PSNR improves (to the encoder input) Also the change is a +-1 in one spot before the IDCT, the IDCT is not bitex= actly specified in MPEG-2 so one could think of this as a correct implementation followed by a IDCT that was sometimes +-1 off instead of spec non compliance Only after the benchmarks and PSNR is presented should we decide if this is a change we want thx [...] --=20 Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB No great genius has ever existed without some touch of madness. -- Aristotle --OptwOoxYdd7hlNT8 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABEIAB0WIQSf8hKLFH72cwut8TNhHseHBAsPqwUCZUC9iQAKCRBhHseHBAsP q+bcAJ9xHqN4MJHxTDpkPOPTlxo1ZGYbtQCdE2fr1Y1KQH46Si4xh1YxfvNIXKU= =MVEZ -----END PGP SIGNATURE----- --OptwOoxYdd7hlNT8-- --===============5589440420657574306== 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". --===============5589440420657574306==--