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Old 12-30-2010, 06:57 AM   #38
Jim Chapman
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Posts: 310
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Join Date: Oct 2009
Device: Lumia 950 Phone
Quote:
Originally Posted by ski_power View Post
Using Freda and ePub brings the device to a crawl when opening relatively large books like any of the Enders' saga.
For mobi format they have an ancient-relic reader called MobiPocket reader for Windows Mobile. When I use that, the page turns are literally instantaneous (as compared to Freda after disabling the page turn animations).

My take from this is that mobi is a slightly 'bigger' format where the file sizes are comparatively larger as compared to ePub, but for weaker hardware the .Mobi runs circles around .ePub which is what Amazon might have been meaning with their statement.
To be honest, the book format (mobi or epub) doesn't have any impact on the speed of a page turn. The reason why Freda turns pages slowly is that it uses some generic (but quite inefficient) operating system APIs to render text onto the screen. MobiPocket probably uses faster APIs (more coding complexity and more risk of incompatibility with new devices ... but better performance).

Conversely, the speed to load a book does depend strongly on the format used. Here, mobi has two advantages over epub:
1) it uses a compression algorithm that lets you uncompress the book's constituent files one at a time, as you open them (whereas an epub archive is just a ZIP file, which is nice and simple, but which does mean that extracting anything at all from the archive means quite a lot of processing work);
2) mobi files contain much simpler book formatting, whereas epub files can contain XHTML in all its richness, with style-sheets and in-line styles and all. A lot of the time that Freda takes to open an ebup book consists of the time that it spends parsing all this XHTML richness (and then ignoring most of it).

Of course the big disadvantage of mobi is that it is a closed proprietary format. If someone wants to give me some C# / .Net code that will unpack and read mobi content, I will incorporate it into Freda tomorrow ... but otherwise it is just too much of a pain to deal with. Of course, as a software writer I see that as a disadvantage ... Amazon no doubt takes a different view!

Just my $0.02's-worth,

Jim

Last edited by Jim Chapman; 12-30-2010 at 07:02 AM.
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