You will also want to ask the vendor some questions regarding compression ratios. According to PC Magazine, compression ratio is "the measurement of compressed data. For example, a file compressed into 1/4th of its original size can be expressed as 4:1, 25%, 75% or 2 bits per byte"
Some of the question you might want to ask the vendor:
- Are there different sizes available?
- How do they break up the large files for dial access?
Here are some examples which might help to explain this.
- Audible.com books come in 4 different formats or sizes. The better the file quality, the bigger the file is. Not all 4 formats will play on all “Audible-ready” players. Format 4 is the best audio quality and also the largest file size, so will take the longest to download down to format 1.
- OverDrive has only one file format/size/quality. Each audio book is broken evenly into one hour listening “chunks” for downloading and burning to CD. In this way, a dial-up user can download a “chunk” at a time.
- NetLibrary has two file format/size/qualities. One they call their “radio quality” format which is recommended for users with a dial up connection. The second is a higher quality format—called their CD quality--which is larger and recommended only for broadband users.
Note: If a user wants to transfer a netLibrary digital audio book to a portable playback device, she must download the CD quality version of the book.