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

Steve Lhomme <slhomme@matroska.org> Mon, 03 December 2018 07:50 UTC

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From: Steve Lhomme <slhomme@matroska.org>
Date: Mon, 3 Dec 2018 08:50:15 +0100
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To: Kieran O Leary <kieran.o.leary@gmail.com>
Cc: Codec Encoding for LossLess Archiving and Realtime transmission <cellar@ietf.org>
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Subject: Re: [Cellar] Mapping of MOV clean aperture values to Matroska
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> >> In Matroska we assume that we override what the codec says.
> >> But I don't think that's how it's handled in ffmpeg. Also there's the
> >> question of what these values apply to: on the decoded surface, which
> >> may include padding on the right/bottom or the area that's supposed to
> >> be visible. In Matroska the "PixelWidth/PixelHeight" correspond to the
> >> visible area, on which we apply extra cropping. (this is currently not
> >> written anywhere).
> >>
> >> As for the MOV atom, is there are spec somewhere ? Or is it clear that
> >> it's some cropping ?
> >
> >
> > I think this is as good of a spec that is freely available - the 'clap section' https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-125850
>
> OK, so we should support it in VLC (which we don't) and that seems to
> map more or less to Matroska values.

I see you submitted a feature request already, excellent
https://trac.videolan.org/vlc/ticket/21179