Animated GIF issues

[ToonPal]

There's an issue that I've experienced in several releases of IrfanView I wanted to share. I've been sticking to IrfanView 3.25 because of how fast it works with animated GIFs. The last releases of 3 and now IrfanView 4 have all been slower and less CPU-efficient with animated GIFs on my system. The older version does have some problems with certain GIFs, but overall, it works pretty good for me(I could probably get a slightly newer version that fixes some of those problems and is still fast).

Some of my GIFs animate slower than intended in the newer versions of the program. For example, I have an 800x600 GIF of a cartoon girl blinking. In 4.00, the blinking is slow-motion, and CPU usage on my 1.4GHz Celeron is almost 50% while 3.25 renders it at full speed(with palette problems) and only needs about 7%.

[Laurent]

Hi ToonPal,

As I mentionned in another reply to you, zooming the gif makes the animation slower. Do you display it at 100 % ?

Laurent

[ToonPal]

Here,

I just completed a series of tests with a high-res animated GIF in several versions of IrfanView. The GIF is 800x600 unzoomed. These are the test results:

3.25 Baseline; GIF animation natural, CPU usage 7%, major palette issues
3.85-3.95 Animation slightly slower, CPU usage 5%, major palette issues
3.97 Animation super slow, CPU usage 100%, application almost unresponsive, minor palette issues
3.99 Animation sluggish, CPU usage 50%, minor palette issues
4.00 Animation sluggish, CPU usage 50%, minor palette issues

I did no zooming in the above tests. Just now, I tried zooming in version 3.95. I blew up the view to 300% while it was animating, and it pushed CPU usage to around 30%. That's still well below the CPU usage of the newer versions rendering at 100% zoom.

Hope this helps.

ToonPal

[Laurent]

Hi ToonPal,

Unluckily, the only idea about the slow animation was the zoom level. I have no further suggestion. Sorry :-(
After your tests, it seems that the palette issues were (almost) solved at the cost of much more CPU usage.
Maybe the processing is less efficient with IrfanView than with your web browser.

Laurent

[ToonPal]

Well, this is the bug report section. And since no workaround is available for this problem, the only remedy is to find and fix the bug.

There have been several high-res GIFs that had no palette problems in any release of IrfanView that became sluggish in version 3.97. There must have been a heck of a change to the code to cause this sudden drop in performance.

Given how long this issue has existed in IrfanView, it makes me wish I'd joined this forum a long time ago.

EDIT: These tests I ran were pretty enlightening. Seeing how IrfanView improved since version 3.25, I figure I might as well upgrade to the last version that still had good animated GIF support(3.95) and take advantage of its features.

EDIT: Whoa! I was just looking through the i_changes.txt for IrfanView and noticed that 3.97 was released April 2005. Hard to believe this bug has existed this long! There's nothing listed in the changes for this version about animated GIFs or any version up to now, including 4.00. I guess a change elsewhere might have had a devastating side-effect on GIF animation that has stuck around up to now(4.00).