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List:       kde-bugs-dist
Subject:    [kdenlive] [Bug 361360] git master (re-opened) - playback speed/framerate slows WAY down when using 
From:       Jean-Baptiste Mardelle via KDE Bugzilla <bugzilla_noreply () kde ! org>
Date:       2016-07-23 9:24:52
Message-ID: bug-361360-17878-sO1FRd6wRu () http ! bugs ! kde ! org/
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https://bugs.kde.org/show_bug.cgi?id=361360

--- Comment #41 from Jean-Baptiste Mardelle <jb@kdenlive.org> ---
Ok, thanks for the infos. I did some more tests, and finally found out the
issue, unrelated to Qt. The qtblend transition (like affine and
frei0r.cairoblend) requests rgba frames to process.

Most videos being in yuv format, this means a conversion has to be done
(probably processed internally by ffmpeg), then the image has to be converted
again in yuv format for display.

Composite transition is a yuv transition which is why it is so much faster.

This does not really explain why the conversion seems to run fast enough for
the first 5 seconds on some systems and then the fps drops, but still this
means that qtblend cannot be easily fixed.

So for the 16.08 release, Vincent and me were thinking to do this:

Introduce a config option to decide compositing mode (could be a combobox in
timeline toolbar):

* disabled
* preview (using composite transition fast but with small luma bleed)
* Hq (slower qtblend but best quality).

We are also planning to remove the individual tracks "enable/disable" composite
since they produce unexpected results, for example disabling a middle track
compositing will make the upper clip disappear).

Would that be ok for you?

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