> On Jul 7, 2017, at 11:32 AM, Derek Buitenhuis <derek.buitenh...@gmail.com> > wrote: > > On 7/7/2017 3:20 AM, Dave Rice wrote: >> Resolves https://trac.ffmpeg.org/ticket/6145 and writes a clap atom that is >> coincident with the frames width and height. >> >> >> From 23d80d0d47829fed61e817b1e7c3f6d420c9ab5c Mon Sep 17 00:00:00 2001 >> From: Dave Rice <d...@dericed.com> >> Date: Thu, 6 Jul 2017 21:12:38 -0400 >> Subject: [PATCH] movenc: write clap tag >> >> --- >> libavformat/movenc.c | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) > > Whoever pushes, add the ticket number into the commit message. > > [...] > >> + avio_wb32(pb, 0); /* horizOff_N (= 0) */ >> + avio_wb32(pb, 1); /* horizOff_D (= 1) */ >> + avio_wb32(pb, 0); /* vertOff_N (= 0) */ >> + avio_wb32(pb, 1); /* vertOff_D (= 1) */ > > Near as I can tell, these related the active image area? Is it useful to ever > set > this to anything but 0 (aka the whole image is active)?
Usually not a good idea to set a denominator to zero. The clap atom documentation at https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-125850 <https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-125850> specifies zero for numerators and one for denominators as default when the ratio of an actual aperture is not used. > Was thinking of stuff like > analogue video, a la http://chromashift.org/aspectratio/. I assume the answer > is > probably 'no’. The atom is analogous to the PixelCrop* elements of Matroska. For instance a standard definition NTSC video may typically be digitized to a frame size of 720x486 but the active image might only be 704x480, so the aperture atom could express the difference. > Patch itself LGTM. […] Thanks, Dave Rice _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
