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Re: excessively slow image animation

From: Evgeny Zajcev
Subject: Re: excessively slow image animation
Date: Wed, 27 Feb 2019 00:50:10 +0300

ср, 27 февр. 2019 г. в 00:19, Daniel Pittman <address@hidden>:
On Wed, Feb 13, 2019 at 9:56 AM Evgeny Zajcev <address@hidden> wrote:
I've got multi frame image at http://lgarc.narod.ru/giphy.mp4
18 seconds to show every frame

Time to fully extract the images from that (cold cache) on my laptop was ~ 30 seconds.  It contains one key frame, the very first, and everything else is a P frame, so to decode frame 20 you need to run forward applying 19 frames worth of data from the start.

If the components were being cached or generated independently – highly likely, I suspect – then that time-cost would be paid the first time.  A grand total of 18 seconds to do that processing doesn't actually sound unreasonable to me, honestly, given that decoding all those frames in individual processes takes ~ 5.35 seconds total on my machine.  It wouldn't take much inefficiency on top of that to bring it up to that rate.

Decoding all the frames takes only 0.25 seconds (see timings for the convert run).  The problem is that Emacs decodes EVERY frame any time you change the image index for the animation, that is how you get 18secs ~= 65 * 0.25

On your machine timings might differ of course


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