[FFmpeg-devel] [RFC] Exporting virtual timelines as stream side data

[Rostislav Pehlivanov]

On 27 March 2018 at 20:44, Derek Buitenhuis <derek.buitenhuis at gmail.com>
wrote:

> So, I know we have edit list "support" in mov.c, but I am steadfast in my
> belief that it is incorrect to implement it at the demuxing layer. By the
> ISOBMFF spec, it is supposed to be applied at the presenattion layer. I'm
> aware we probably cannot remove the current implementation very easily
> (or at all?) because many will argue it is "removing a feature". Thus, for
> ISOBMFF and mov support, this will likely have to live under a movflag,
> I assume?
>
> Anyway, this is my proposal for generic stream side data for virtual
> timelines.
> This is also meant to cover Matroska ordered chapters and editions, though
> I
> am not entirely sure how segment linking would work into this, if I am
> honest.
>
> If/once I have the side data structs and API (in the following RFC patch)
> agreed
> upon, I am willing to write:
>
>     * Support for exporting MOV/ISOBMFF edit lists via side data
>     * Support for exporting Matroska edit lists via side data
>     * Porting the fftools to use it (if wanted)
>
> As a side note, I would appreciate input from someone who unerstands
> Matroska
> better than I do on this. I haven't included e.g. the Hidden/Enabled flags
> in
> AVtimelineEntry since they don't seem to actually be useful to the actual
> timeline (they seem to be mostly related to displaying chapter names or
> not).
>
> The side data structs and API are based off of the recently pushed
> encryption
> side data changes. The media rate is a rational, because exporting a float
> would change on different platforms, and would make adding regression tests
> problematic.
>
> So, everyone, rev up your diesel powered bikesheds and drive them full
> steam
> into this thread's back yard, over my daffodils.
>
> Derek Buitenhuis (1):
>   avcodec/avutil: Add timeline side data
>
>  libavcodec/avcodec.h |   8 +++
>  libavutil/timeline.h | 160 ++++++++++++++++++++++++++++++
> +++++++++++++++++++++
>  2 files changed, 168 insertions(+)
>  create mode 100644 libavutil/timeline.h
>
> --
> 1.8.3.1
>
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I think we should drop the internal crap if the tools and the API support
it. Would also solve a lot of issues like ffmpeg.c not trimming the start
frame (so people complain all the time about longer files).