excessively slow image animation

[Evgeny Zajcev <lg.zevlg@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1413 bytes --]

I've got multi frame image at http://lgarc.narod.ru/giphy.mp4

And run next code on it:

  (let ((ctime (float-time)))
    (setq img (create-image "~/tmp/giphy.mp4" 'imagemagick nil :scale 1.0))
    (insert-image img)
    (cl-dotimes (index 65)
      (image-show-frame img index 'nocheck)
      (sit-for 0.0))
    (- (float-time) ctime))
  ==> 18.788017988204956

18 seconds to show every frame

Then I simple converted the file to set of bmp files:

  $ time convert ~/tmp/giphy.mp4 ~/tmp/anim1/giphy%05d.bmp
  convert ~/tmp/giphy.mp4 ~/tmp/anim1/giphy%05d.bmp  0,18s user 0,10s
system 117% cpu 0,237 total
  $

And animated on these bmp files:

  (let ((ctime (float-time)))
    (setq img (create-image "~/tmp/anim1/giphy00000.bmp" 'imagemagick nil
:scale 1.0))
    (insert-image img)
    (cl-dotimes (index 65)
      (plist-put (cdr img) :file (format "~/tmp/anim1/giphy%05d.bmp" index))
      (force-window-update)
      (sit-for 0.0))
    (- (float-time) ctime))
  ==> 1.3518333435058594

Now I use method with bmp files.  I would like to use built in `:index'
image property to animate images, however current animation speed is
totally not acceptable.  Can this be fixed, or am I doing something wrong?

Thanks

--Versions--
EMACS: GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
3.18.9) of 2018-11-13
IM: Version: ImageMagick 6.8.9-9 Q16 x86_64 2018-09-28
http://www.imagemagick.org

-- 
lg

[-- Attachment #2: Type: text/html, Size: 2337 bytes --]