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 530F7456B2 for ; Thu, 20 Apr 2023 06:43:02 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 187EC68A9F0; Thu, 20 Apr 2023 09:43:00 +0300 (EEST) Received: from mail0.khirnov.net (red.khirnov.net [176.97.15.12]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id C3D7A680969 for ; Thu, 20 Apr 2023 09:42:53 +0300 (EEST) Received: from localhost (localhost [IPv6:::1]) by mail0.khirnov.net (Postfix) with ESMTP id 823832404EE for ; Thu, 20 Apr 2023 08:42:53 +0200 (CEST) Received: from mail0.khirnov.net ([IPv6:::1]) by localhost (mail0.khirnov.net [IPv6:::1]) (amavisd-new, port 10024) with ESMTP id QZapoYBfO0DR for ; Thu, 20 Apr 2023 08:42:52 +0200 (CEST) Received: from lain.khirnov.net (lain.khirnov.net [IPv6:2001:67c:1138:4306::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "lain.khirnov.net", Issuer "smtp.khirnov.net SMTP CA" (verified OK)) by mail0.khirnov.net (Postfix) with ESMTPS id 8482E2404EC for ; Thu, 20 Apr 2023 08:42:52 +0200 (CEST) Received: by lain.khirnov.net (Postfix, from userid 1000) id 684521601B2; Thu, 20 Apr 2023 08:42:52 +0200 (CEST) From: Anton Khirnov To: FFmpeg development discussions and patches In-Reply-To: <20230419221248.GV275832@pb2> References: <20230419194832.757-1-anton@khirnov.net> <20230419205302.GU275832@pb2> <168193836938.9711.9672747873724950733@lain.khirnov.net> <20230419221248.GV275832@pb2> Mail-Followup-To: FFmpeg development discussions and patches Date: Thu, 20 Apr 2023 08:42:52 +0200 Message-ID: <168197297239.3843.14731420441297889856@lain.khirnov.net> User-Agent: alot/0.8.1 MIME-Version: 1.0 Subject: Re: [FFmpeg-devel] [RFC/PATCH] fftools/ffmpeg: stop printing PSNR information in status report 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: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: Quoting Michael Niedermayer (2023-04-20 00:12:48) > On Wed, Apr 19, 2023 at 11:06:09PM +0200, Anton Khirnov wrote: > > Quoting Michael Niedermayer (2023-04-19 22:53:02) > > > On Wed, Apr 19, 2023 at 09:48:32PM +0200, Anton Khirnov wrote: > > > > When an encoder exports sum-of-squared-differences information in > > > > encoded packets, print_report() will print PSNR information in the > > > > status line. However, > > > > > > > * the code computing PSNR assumes 8bit 420 video and prints incorrect > > > > values otherwise; there are no issues on trac about this > > > > > > Are the values in the "otherwise" case maybe good enough so they > > > worked for people with noone noticing ? > > > > While working on this with a 10bit sample I was suprised this code and > > vf_psnr showed significantly different values (IIRC not even the first > > digit was accurate) and it took me a while to realize the scaling made > > the assumptions it did. > > > > > > * only a few encoders (namely aom, vpx, mpegvideo, snow) export this > > > > information; other often-used encoders such as libx26[45] do not > > > > export this, even though they could > > > > > > > > This suggests that this feature is not useful and it is better to remove > > > > it rather than spend effort on fixing it. > > > > --- > > > > I needed to resolve this code's interaction with encoders as a part of > > > > my multithreading work and spent a few hours on it. Making it work > > > > correctly in all cases seems nontrivial and duplicates a lot of the > > > > logic from vf_psnr. > > > > > > Can anything missing in vf_psnr be added into it and then vf_psnr used ? > > > I agree that duplicating PSNR code and logic is bad > > > > Nothing is missing in vf_psnr AFAIK, the difference is that these values > > are produced directly by the encoder, so you don't need a > > decoding+filtering pass to obtain the numbers. > > That sounds like a missing feature. > vf_psnr cannot use the encoder values, it always needs to recompute them. > The encoder could export these values in metadata and vf_psnr could > then check if the frame pairs already have their psnr computed and use > that. In general I agree that making those values more widely usable would be good, but there's a number of issues that would need to be addressed first: * encoders export encoded packet properties, but AFAIK no muxer can store them * even if a muxer could store them or encoded packets could be directly passed to a decoder (this should actually be possible once I'm done with this work), the data is only defined for packets and not frames * possibly something like showinfo would be more suited for displaying this None of these are insurmountable, but it's a fair amount of work. Patches welcome. > > The question more broadly is - what is this supposed to be useful for? > > PSNR is a highly flawed metric and AFAIU state of the art moved several > > generations away from it. And for a quick-and-dirty quality estimate, > > the bitrate and QP might be more informative for most users, and are > > supported by more encoders. So what is the point of printing this > > information? > > The "problem" isnt psnr specific > having a filter which could provide another metric and be able to use > encoder supplied data when available or compute them from encoder input + > decoded images in a way that is automatic would be useful > It would mean a single syntax a user could use to get the metric he wants > while using the optimal implementation The problem is PSNR-specific code in ffmpeg CLI that is blocking my work. Sounds to me we are in agreement that this code should not be there. -- Anton Khirnov _______________________________________________ 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".