EPUB files take long time to open

[betelguese]

Hi all, I tried searching the web for a solution to no aid. Issue is that EPUB files (an ebook file format) take a very long time to open, and even after opened, browsing pages inside the epub is slow. It does not matter if I open the book with Calibre or SumatraPDF, I even tried different extensions inside Firefox or Edge, it's always slow, sometimes taking up to 2 or 3 minutes to open, and SumatraPDF sometimes not even opening and staying in task manager as a high CPU process forcing me to terminate it. Disabling Windows Defender is of no help and changing the Graphics Performance preference (GPU assisted or disabled) does not fix it. I'm using a Dell XPS Windows 10 laptop. Thanks for any hint.

[PeterT]

How large are the individual XHTML files inside the Epub?

Sent from my Pixel 7a using Tapatalk

[betelguese]

Originally Posted by PeterT

How large are the individual XHTML files inside the Epub?

Sent from my Pixel 7a using Tapatalk

Hi, how can I check that? Also, this issue happens with ANY Epub file, so I guess it's non related to the individual XHTML files inside of it

[JSWolf]

Is your computer slow?

[Quoth]

Something somewhere is broken if the Calibre Viewer does this with every epub.

I've only used Sumatra for PDFs.

I have a 2016 laptop with Win10 and it's pretty instant to open epubs with Calibre viewer. A browser is madness.

[sgmoore]

I had issues with one version of Sumutra (can't remember which because I deleted it).
But SumatraPDF-3.3.3-64.exe and the prelease work fine.

As a comparison, they load Pickwick Papers (953 pages) (see https://www.gutenberg.org/ebooks/580.epub3.images ) in less than a second for version 3.3.3 . This is on my 5 year old Windows 10 machine.

Calibre Viewer on the other hand has always been slow and takes about 10 seconds before anything appears to happen and another 5 seconds until I can start reading.

[Sirtel]

Originally Posted by sgmoore

Calibre Viewer on the other hand has always been slow and takes about 10 seconds before anything appears to happen and another 5 seconds until I can start reading.

Calibre Viewer became slow when the version 4.x was introduced and the viewer was completely rewritten. Before that the viewer was pretty snappy. For this reason I still use the viewer from 3.48 (Calibre itself is current).

[Quoth]

Originally Posted by betelguese

…
it's always slow, sometimes taking up to 2 or 3 minutes to open, and SumatraPDF sometimes not even opening and staying in task manager as a high CPU process forcing me to terminate it.

Originally Posted by sgmoore

…
Calibre Viewer on the other hand has always been slow and takes about 10 seconds before anything appears to happen and another 5 seconds until I can start reading.

That's not slow. I agree it's not instant. Re-read the OP.

Something is broken. 120 to 180s seconds vs 15s is x10 slower.

My 2017 Dell Optiplex 7050 takes 7 s first time, 3 to 4s subsequent. (SSD for OS, SATA HDD for user files). The 2016 Win10 laptop is certainly slower as it's got no SSD. But faster than opening Firefox or Word the first time.

Calibre 7.8

[Comfy.n]

Sumatra can't be slow on any well-functioning system. I wonder what happens in Windows Safe Mode

[PeterT]

I wonder what is the source of the Epub?

Sent from my Pixel 7a using Tapatalk

[Karellen]

Maybe its one of those ebooks where there is no text, rather it contains large sized tiffs of the scanned pages.

[Sirtel]

Originally Posted by Karellen

Maybe its one of those ebooks where there is no text, rather it contains large sized tiffs of the scanned pages.

The OP said it happens with any epub file, so it's probably not the epubs.

[betelguese]

Originally Posted by JSWolf

Is your computer slow?

No, my computer is perfectly fine, everything snappy and optimized for high performance (no unnecessary processes in the background, minimal scheduled tasks and services, etc). Dell XPS 9710 with high specs.

Originally Posted by sgmoore

I had issues with one version of Sumutra (can't remember which because I deleted it).
But SumatraPDF-3.3.3-64.exe and the prelease work fine.

As a comparison, they load Pickwick Papers (953 pages) (see https://www.gutenberg.org/ebooks/580.epub3.images ) in less than a second for version 3.3.3 . This is on my 5 year old Windows 10 machine.

Calibre Viewer on the other hand has always been slow and takes about 10 seconds before anything appears to happen and another 5 seconds until I can start reading.

Wow, I downloaded that EPUB for a test and yes, SumatraPDF opens it instantly, first EPUB I get this positive result! But the reason might be that this EPUB only has text, no images at all. By the way, I have the latest SumatraPDF v3.5.2 64bit. Calibre on the other hand opens it faster than the other EPUBs I have but still much slower than Sumatra (latest Calibre v7.9.0)

Originally Posted by Sirtel

Calibre Viewer became slow when the version 4.x was introduced and the viewer was completely rewritten. Before that the viewer was pretty snappy. For this reason I still use the viewer from 3.48 (Calibre itself is current).

How can you update Calibre to latest version while keeping an older version of the viewer? Also, any way of downloading the Viewer from version 3.48 so I can test it? I was able to download Calibre v3.48 but not the viewer as a standalone. Thanks

[BetterRed]

@betelguese - try Thorium or Azardi, in my experience they're both faster than the Calibre viewer. Haven't used Sumatra for decades.

BR

[Sirtel]

Originally Posted by betelguese

How can you update Calibre to latest version while keeping an older version of the viewer? Also, any way of downloading the Viewer from version 3.48 so I can test it? I was able to download Calibre v3.48 but not the viewer as a standalone. Thanks

The way I did it is that first, I unchecked all file formats in the internal viewer preferences (Calibre - Preferences - Behavior). Then I downloaded Calibre Portable 3.48 from here and associated the ebook formats with its viewer. Now, when I have the current Calibre open and click on a format, it opens in the old viewer. Same with opening ebooks outside Calibre.