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07-22-2012, 09:51 AM | #1 |
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How to speedup page turn on sideloaded epub on Kobo Touch with Firmware 2.0
In the last 2 days I've done many test on my brand new Kobo Touch upgraded with firmware 2.0.0 (r41166 12/07/12)
I've found a way to speed up the infamous slow page turn on sideloaded epub with firmware 2.0 Short Q/A: *) will this trick make a sideloaded epub fast as a kepub? No, it wont. *) will this trick make a sideloaded epub faster? Yes, it will. Long story short: if you use Calibre, you need to change a value in the epub output options. Change the "Split file larger than" parameter from it's default value (260Kb) to the minimum value of 25Kb I've attached some screenshots that show how to change this parameter. Backup your library before proceeding further :-) After changing the "Split file larger than" parameter to 25Kb, you need to regenerate you epub files. You can regenerate the epub from the original source (RTF/PDF/ODT/TXT...) if any... or you can generate a new epub starting from the original epub. Calibre will take care of that. Now, how much faster/slower are sideloaded epub vs. kepub books? I gathered the following data using my webcam, and counting the number of frame between page refresh. I start counting when my finger touch the screen, I stop counting when the new page look "final" on the screen (the Kobo need 3/4 frame (of my webcam) to "finish up" the rendering of any page shown) My webcam goes at 30fps, so we have a precision of about 0,03sec. For any measure I've counted the number of frame took by 6 pages turn (5 partial pages turn and 1 full page turn) and then I've calculated the average value. First thing discovered: a partial page refresh employ the exact same time of a full page refresh. So, partial page refresh are not faster nor slower than full page refresh. Now, here is the page turn speed data: Kepub book: 1,26 sec Sideloaded epub: 1,93 - 3,52 sec Optimized Sideloaded epub: 1,71 - 2,21 sec The page turn speed on epub depend heavily from the internal epub structure. I've looked at the internal of some epub/kepub books: in general, bigger and complex html files mean slower page turn. This is why telling Calibre to split html file every 25Kb make the page turn faster. The page turn speed on the same epub will also change depending on which page you are, I suspect that it depend on how much data the kobo need to elaborate to show the specific page you are reading. During my experimentation I've tested many kind of optimization (remove style, remove image, change the html split file size, change the compression algorithm parameter....) I've done test on epub optimized in more than 30 different way. The only thing that give any useful result is this "Split file larger than 25kb" parameter optimization. This optimization impact on more than the simple page turn speed. The whole epub experience became faster. The goto page function is much more responsive. On an standard epub you can wait 3 or 4 second before the page refresh... on an optimized epub this is much faster (I didn't measure it, but it's about 3 or 4 time faster). Here is some of the video I shot with my webcam: Kepub Standard Epub (no optimization) Optimized Epub (Calibre "Split file larger than 25kb" parameter) Another interesting video is the closeup of the page refresh. It's interesting to see how the page refresh unfold out frame by frame. To see it frame by frame you probably need to download the video and use a player like the MediaPlayerClassic This optimization work for me on my epub. I've tested different epub, and I've seen that the impact of this optimization vary book-by-book. Anyway, an optimized epub is always faster than the standard version of the same epub, in the worst case scenario, the page turn speed is the same, but it only happened in a single case during my testing. I'm very curious to know if this optimization works for other people too. Another interesting thing is the impact of page turn speed on the reading experience. Now, I know that in best case scenario, an optimized epub is only 0,5 sec slower than a kepub (1,7 sec vs. 1.2 sec) but the real experience is that IT FEEL much slower. The reality is that a reaction time of 1,2 sec seem near instantaneous, whether a reaction time of 1,7 sec doesn't, it feel slow, it feel like a pause, an interruption in the flow of what i was doing. About the usability, keep in mind that the worst case scenario is is 1.2 sec vs. 3.5 sec (on an unoptimized epub). It is slow as a turtle.... :-| Please Kobo Dev Team, fix this slow page turn on sideloaded epub. Last edited by MisterMax; 07-22-2012 at 09:58 AM. |
07-22-2012, 10:30 AM | #2 |
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This explains why I don't have the slow page turn bug.
My ePubs are split into chapters. It looks like the Touch firmware is figuring out something to do with the entire chapter every time you turn a page. Why they aren't using the time when you are reading a page to pre-process the most likely next event (page forward) is a mystery to me. |
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07-22-2012, 10:42 AM | #3 | |
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They should simply pre-render the next/previous page in a buffer, and show it when the user turn page (and then prerender the next page...) This will make for near-instantaneous page turn, without any added cost. I'm a software dev, so I know that prerender a page is not something you can implement in some hours of work... but the benefit for the user experience will be huge! |
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07-22-2012, 10:45 AM | #4 | |
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It doesent matter how small the single html file are in an epub, in my experience event an optimized epub will always be slower than an kepub. The kepub contain specific css, and specific javascript code, and the html have a different structure from the epub generated by calibre. Maybe that the kepub contain some kind of structural information that help the Kobo to render the page faster... |
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07-22-2012, 12:24 PM | #5 | |
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Thanks for doing this research; I really appreciate how thorough you are. |
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07-22-2012, 12:31 PM | #6 |
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Is that in seconds? My KT is flipping pages in under 1 second.
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07-22-2012, 12:48 PM | #7 |
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Yes I've measured in seconds.
Are you sure? Do you have measured it? Or is it your "feeling"? I took mi measurement from when my finger touch the screen, to when the screen finish to draw and finalize the new page. During my measurement my feeling was that a Kepub was near-instantaneous... but in reality the Kepub take 1,2 sec to turn the page. |
07-22-2012, 01:20 PM | #8 |
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You're right about the "feel" being off, even if the actual page turn speed isn't that much lower. I couldn't stand how sluggish reading seemed with the new firmware, so ended up downgrading.
I don't want to complain too much though, since the Touch is a much better product now than the buggy mess that launched. It's nice that they're supporting it so well. Even easier than this is downgrading to the previous firmware. |
07-22-2012, 02:03 PM | #9 |
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Like everything you do daily after a day or 2 you adapt to slow page turns. I still read sometimes on Kobo wifi and when switching back to KT would notice I was turning pages before finished reading the page. This worked without problems on Kobo wifi as early page turn was then timed just right. The same will happen reading on KT with 2.0 firmware. 2.0 loading library covers as needed works good. A little slow because loading covers on new page but still good enough. On my Sony T1 I had to turn off cover display for library to be usable with 2000 books. Being able to turn off covers in large KT library should also be a big improvement.
Adding books to shelves really needs improvement as it is slow process and locked up the reader when I added hundreds of books to one shelf then tried to add hundreds more on a prior 2.0 install. I'll try that stress test again this week with my latest 2.0 install. |
07-22-2012, 03:11 PM | #10 |
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Yes, this is a very nice thing that few dev team do.
This is one of the thing that made me purchase a Kobo Touch instead that other devices (To be precise I own 2 Kobo Touch, one for me and one for my girlfriend :-)) |
07-22-2012, 03:39 PM | #11 |
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25Kb is going to make some really poor spots to split on. Plus, it's a very bad idea to do an ePub > ePub conversion as has been mentioned many times on MR.
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07-22-2012, 03:50 PM | #12 | |
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Sorry I don't get the point...
what's the practical meaning of "some really poor spots to split on" The only drawback I've seen is that the epub are about between 10% and 20% bigger (this is because the compression algorithm used by epub is less efficient on many small file) Quote:
Probably the ePub > ePub conversion should be seen as the last resort |
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07-22-2012, 07:19 PM | #13 | |
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Quote:
As for splitting up the files. Yes you can get some pretty poor spots to split on. Since you are splitting the files inside by size rather than by chapters and the Kobo pagebreaks after every file, you will get pages of text that simply end with a lot of white space at the end but then have the text continue on on the next page. So you could end up with 2 sentences on one page and the rest of the text on the other. Last edited by Danger; 07-22-2012 at 07:23 PM. |
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07-22-2012, 07:50 PM | #14 |
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Also remember that if you make a change like this, you may regret it when the version with the fix for this is released.
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07-22-2012, 08:09 PM | #15 |
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