On Wed, Dec 31, 2014 at 01:33:44PM +0100, Nicolas George wrote: > Le decadi 10 nivôse, an CCXXIII, Clement Boesch a écrit : > > From: Clément Bœsch <clem...@stupeflix.com> > > > > --- > > Another approach this time: exporting a filtergraph from the demuxer > > (when requested) and inserting it in the tools automatically. > > > > FIXME: doesn't work when using -ss with ffmpeg, maybe because it's > > shifting the timestamps of the frames before feeding them to > > libavfilter. I probably need guidance here. > > I suspect it aims at a similar goal than this patch series: > > http://ffmpeg.org/pipermail/ffmpeg-devel/2014-February/154783.html > > Did you have a look at it? It has the benefit of working at the demuxer and > decoder level, without lavfi. > > At the time, I was stuck by strange threading problems, I have not yet > looked at it again. >
Yes, I also tried to do it at demuxer level, but keep in mind that the mov edit list needs some timing adjustment (after you trim in the middle). 15:30:23 <@ubitux> wm4: so... doing it at demuxer level is kind of annoying because of the dts (i believe) 15:31:04 <+wm4> hm? 15:31:06 <@ubitux> i mean, for the packet that are supposed to be dropped, i can't really adjust the dts 15:31:46 <@ubitux> but then after you get back packet to be presented, these must be time adjusted (both pts... and actually dts) 15:32:04 <@ubitux> and so you get dts smaller than the previous ones that were not supposed to be presented 15:32:10 <@ubitux> and it's a mess 15:32:16 <@ubitux> but maybe i miss a trick somewhere 15:32:25 <@ubitux> i'd say i'd just don't touch the dts and only the pts 15:32:29 <@ubitux> but it breaks badly 15:33:27 <+wm4> hm 15:35:33 <@ubitux> http://b.pkh.me/0001-avformat-RFC-WIP-add-basic-timeline-support.patch 15:35:42 <@ubitux> it would look like this 15:35:44 <@ubitux> but it doesn't work. 15:36:18 <@ubitux> so it looks appealing, but unless i find a way to adjust the pts/dts properly, it can't work 15:38:43 <@ubitux> in theory i'd say that not changing the dts is the correct thing to do 15:38:57 <@ubitux> but unfortunately ffmpeg doesn't like the inconsistency between pts and dts 15:40:58 <+wm4> no, dts and pts must be consistent 15:41:54 <+wm4> hm possible we could create another mechanism that changes the timestamps after decoder 15:41:57 <+wm4> *possibly 15:42:44 <+wm4> but yeah, it's a mess Basically, in case this is not clear, for the packets that must be decoded (but not presented / needed to decode the frame that will be presented later), we don't know what timing and dts to set, because they overlap (you need to avoid a time wrap for the segments you remove). -- Clément B.
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