[Bug]: avif Performance

[TristisOris]

Preflight Checklist

• I have searched the issue tracker for a bug report that matches the one I want to file, without success.

OpenComic Version

1.6.6 39e7985

Operating System

win11

Installed via

exe

Steps to reproduce

I came across a manga where every page opens with a very long delay. The second page takes about 5-10 seconds, the rest take 1-2 seconds each.
Small archives of 20-50 MB, but the files are in .avif format — could that be the problem?

Expected Behavior

Actual Behavior

Error message

No response

Additional Information

No response

Sample file

No response

[ollm]

That's unusual. Would you mind sending me the file by email so I can test it? oleguer.llopart.mora@gmail.com

Also, which reading mode/settings are you using? Slide, Vertical, Double Page, etc.?

[ollm]

I've tested the files, and yes, they are slow. This is due to the combination of the avif format, which is slower to decode, and the fairly high image resolution of 3288x4800 (They have been AI upscaled).

However, I think OpenComic makes the situation even worse because of thumbnail generation. The 5–10 second delay you mentioned when opening the second page is most likely caused by this.

When opening a file, OpenComic first renders the visible pages (1 or 2 in double page mode). It then displays them and starts generating thumbnails while also rendering additional pages (10 by default, although this depends on your settings). I believe this is where the bottleneck is. It seems that multiple avif images cannot be decoded in parallel. My guess is that decoding a single avif image already uses all available CPU cores, so they end up being processed one at a time.

I'll see if there's any way to improve this last part, although I think it will be quite difficult.

[ollm]

I've optimized the image loading/rendering order f78a1d5. The improvement is most noticeable with images that take longer to decode, such as very high resolution images or slower formats like avif.

The process now works as follows, when opening a file, the visible images are rendered first (1 or 2 in double page mode), then the preload images (10 by default), and finally the thumbnails are generated.

I haven't tested it on Windows yet, but on Linux (Ubuntu) it significantly improves the rendering speed of these types of images (I tested in your sample files).

Nightly builds: ollm/OpenComic-Nightly

[TristisOris]

Yeah, it much faster now. First 10 without delay, then some load happens every ~3 pages.

[ollm]

I'm glad the performance has improved. That load is probably coming from rendering the next pages and generating thumbnails as well as you progress through.