Re: [Cellar] Mapping of MOV clean aperture values to Matroska

Dave Rice <dave@dericed.com> Sun, 25 November 2018 20:20 UTC

Return-Path: <dave@dericed.com>
X-Original-To: cellar@ietfa.amsl.com
Delivered-To: cellar@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9E3AE1292AD for <cellar@ietfa.amsl.com>; Sun, 25 Nov 2018 12:20:06 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.121
X-Spam-Level:
X-Spam-Status: No, score=-1.121 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_NEUTRAL=0.779] autolearn=no autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VDbLzmfpWFXH for <cellar@ietfa.amsl.com>; Sun, 25 Nov 2018 12:20:04 -0800 (PST)
Received: from server172-3.web-hosting.com (server172-3.web-hosting.com [68.65.122.111]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 416641288EB for <cellar@ietf.org>; Sun, 25 Nov 2018 12:20:04 -0800 (PST)
Received: from cpe-104-162-94-162.nyc.res.rr.com ([104.162.94.162]:40598 helo=[10.0.1.17]) by server172.web-hosting.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from <dave@dericed.com>) id 1gR0sp-003FWR-P3; Sun, 25 Nov 2018 15:20:03 -0500
Content-Type: text/plain; charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 12.0 \(3445.100.39\))
From: Dave Rice <dave@dericed.com>
In-Reply-To: <CAO7v-1Qci+eGHBbQYuHYn-fSb+WA+ac-=Z89zkcdcYpQaKGQEw@mail.gmail.com>
Date: Sun, 25 Nov 2018 15:19:58 -0500
Cc: cellar@ietf.org
Content-Transfer-Encoding: quoted-printable
Message-Id: <353D4CFD-370C-4509-B7BE-3D572EC2DEFB@dericed.com>
References: <CAO7v-1Qci+eGHBbQYuHYn-fSb+WA+ac-=Z89zkcdcYpQaKGQEw@mail.gmail.com>
To: Kieran O Leary <kieran.o.leary@gmail.com>
X-Mailer: Apple Mail (2.3445.100.39)
X-OutGoing-Spam-Status: No, score=-2.9
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - server172.web-hosting.com
X-AntiAbuse: Original Domain - ietf.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - dericed.com
X-Get-Message-Sender-Via: server172.web-hosting.com: authenticated_id: dave@dericed.com
X-Authenticated-Sender: server172.web-hosting.com: dave@dericed.com
X-Source:
X-Source-Args:
X-Source-Dir:
X-From-Rewrite: unmodified, already matched
Archived-At: <https://mailarchive.ietf.org/arch/msg/cellar/OKemOq5Ha6l9rgT6pQQA4QErJSM>
Subject: Re: [Cellar] Mapping of MOV clean aperture values to Matroska
X-BeenThere: cellar@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Codec Encoding for LossLess Archiving and Realtime transmission <cellar.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/cellar>, <mailto:cellar-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/cellar/>
List-Post: <mailto:cellar@ietf.org>
List-Help: <mailto:cellar-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/cellar>, <mailto:cellar-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 25 Nov 2018 20:20:07 -0000

Hi Kieran,

> On Nov 23, 2018, at 4:56 AM, Kieran O Leary <kieran.o.leary@gmail.com>; wrote:
> 
> Hi,
> 
> Would I be correct in saying that ideally, Clean Aperture values in a
> MOV/MPEG-4 file should map to the PixelCrop element in Matroska?

Yes, they conceptually do the same thing but I’m a little confused about how to use the vert/horiz offset fractions of the clap atom to convert to the pixel crop atom. I tried in both QuickTime 7 and X, and while QuickTime X uses the cleanAperature w/h fractions to present a cropped image, QuickTime 7 doesn’t but appears to adjust the aspect ratio according to those values. QuickTime X does seem impacted by non-zero offset values not in a way that I consider coherent. Do you have any examples of un-centered aperatures? I was hoping that IMX files would, does the ones I have don’t use any aperature.

> I'm asking about this in regards to this ffmpeg ticket -
> https://trac.ffmpeg.org/ticket/7437
> As it appears that FFmpeg does not currently read the values in the
> clap atom and it also does not map them to Matorksa files when
> remuxing. It seems to make the most sense to map them to PixelCrop,
> but I'd like to hear it from folks more knowledgable than me.

Seems reasonable to me, but I’m not exactly certain what the mapping would be.

> Another associated issue with the display of these kinds of values is
> with VLC as it appears that
> 
> 1) PixelCrop values in Matroska are not supported by VLC at the moment
> - https://trac.videolan.org/vlc/ticket/21192
> 2) Clean aperture values are not supported by VLC at the moment
> https://trac.videolan.org/vlc/ticket/21179

Sounds like these tickets are in my priority order as well.
Dave Rice