Epub file sizes

jerryleejr · 07-27-2008, 02:37 PM

Has anyone noticed the size difference in Epub files and the same books in other formats?? It seems that the Epub's are smaller.

JJ

llasram · 07-27-2008, 11:17 PM

Quote:

Originally Posted by jerryleejr

Has anyone noticed the size difference in Epub files and the same books in other formats?? It seems that the Epub's are smaller.

I did notice that Epub seems to be a touch smaller than LIT; I haven't compared it to Mobipocket, but it may well be. Most pre-Epub formats have all kinds of optimizations to decrease CPU and RAM usage in an e-book rendering application, like using lightweight compression and separately compressing fairly small file chunks (to facilitate seeking without needing to de-compress the entire file). Epub instead uses the fairly good DEFLATE algorithm across entire files, which is as good as you can get without requiring that a renderer decompress everything in the book in order to render anything.

kovidgoyal · 07-27-2008, 11:43 PM

Its completely a block size thing. In LRF for example every chapter is separately compressed. If you follow adobes guidelines and put every chapter into a separate file then I suspect you wont see any significant size differences between LRF and epub.

MOBI on the other hand compresses the entire text sream, but it supports 3 levels of compression

0 - no compression
1 - palmdoc (a lightweight compression scheme)
2 - huffman coding (this should actually outperform DEFLATE for pure text)

slayda · 07-28-2008, 09:43 AM

As kovid indicates, some compression is more effective the more that gets compressed. While other compression schemes can actually enlarge some files, e.g. RLE compression.

HarryT · 07-28-2008, 01:13 PM

High compression on Mobi files takes forever even on a fast machine. Personally I never use it. Mobi advise its use only for extremely large books, like dictionaries.

slayda · 07-28-2008, 01:18 PM

Now that I know that Epub files can be "unzip", I would imagine that the Epub files use a variant of the LZW compression. With it, typically large files compress more than smaller files due to the nature of the compression methodology. Therefore if the individual chapters are compressed individually, there will be (normally) less compression than if the entire book is compressed as a unit.

igorsk · 07-28-2008, 03:09 PM

EPUB uses standard Flate compression of the ZIP container.

07-27-2008, 02:37 PM	#1
jerryleejr Koby-rific! Posts: 944 Karma: 191112 Join Date: Jan 2008 Location: 2' From My MacBook Pro Device: Kobo Sage,Kobo Aura One, Glo HD,PRS-T1,PRS-950, PRS 300, PRS 350	Epub file sizes Has anyone noticed the size difference in Epub files and the same books in other formats?? It seems that the Epub's are smaller. JJ

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
varying epub sizes	jjansen	ePub	3	09-03-2010 05:10 PM
How can i convert HTML or txt file to EPUB file ?	guguqiaqia	ePub	7	05-28-2010 09:15 PM
Splitting large file sizes ...	Hangman	Calibre	1	04-05-2010 10:01 PM
eBook File Sizes Compared	Colin Dunstan	Workshop	2	09-15-2003 11:08 AM

07-27-2008, 11:43 PM	#3
kovidgoyal creator of calibre Posts: 45,110 Karma: 27110892 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Its completely a block size thing. In LRF for example every chapter is separately compressed. If you follow adobes guidelines and put every chapter into a separate file then I suspect you wont see any significant size differences between LRF and epub. MOBI on the other hand compresses the entire text sream, but it supports 3 levels of compression 0 - no compression 1 - palmdoc (a lightweight compression scheme) 2 - huffman coding (this should actually outperform DEFLATE for pure text)

07-28-2008, 09:43 AM	#4
slayda Retired & reading more! Posts: 2,764 Karma: 1884247 Join Date: Sep 2006 Location: North Alabama, USA Device: Kindle 1, iPad Air 2, iPhone 6S+, Kobo Aura One	As kovid indicates, some compression is more effective the more that gets compressed. While other compression schemes can actually enlarge some files, e.g. RLE compression.

07-28-2008, 01:13 PM	#5
HarryT eBook Enthusiast Posts: 85,544 Karma: 93383043 Join Date: Nov 2006 Location: UK Device: Kindle Oasis 2, iPad Pro 10.5", iPhone 6	High compression on Mobi files takes forever even on a fast machine. Personally I never use it. Mobi advise its use only for extremely large books, like dictionaries.

07-28-2008, 01:18 PM	#6
slayda Retired & reading more! Posts: 2,764 Karma: 1884247 Join Date: Sep 2006 Location: North Alabama, USA Device: Kindle 1, iPad Air 2, iPhone 6S+, Kobo Aura One	Now that I know that Epub files can be "unzip", I would imagine that the Epub files use a variant of the LZW compression. With it, typically large files compress more than smaller files due to the nature of the compression methodology. Therefore if the individual chapters are compressed individually, there will be (normally) less compression than if the entire book is compressed as a unit.

07-28-2008, 03:09 PM	#7
igorsk Wizard Posts: 3,442 Karma: 300001 Join Date: Sep 2006 Location: Belgium Device: PRS-500/505/700, Kindle, Cybook Gen3, Words Gear	EPUB uses standard Flate compression of the ZIP container.

Advert

Advert