The ePUB file type is an open source format developed by the International Digital Publishing Forum (IDPF) . Based on XHTML, XML and CSS it works well with a number of software applications which has helped the popularity of the format grow. Despite this, there are a raft of rules that must be adhered to when creating an ePUB file which has attracted criticism of the format. The format allows DRM protection to be added to a file.
The ePUB format allows reflowable content. This means that the content fits the size and shape of the screen it is being displayed upon, in the same way that text on an HTML page changes depending on the size of the display. An ePUB file tends to consist of three elements: archive, metadata and content.
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MP3 is a digital music format which allows CD tracks to be reduced to around a tenth of their normal size without a significant loss of quality. MP3 gets rid of a lot of the information recorded in a song that our ears are not able to hear and then uses complex algorithms to reduce the file size. This then enables you to get hundreds of songs on to a CD and it also has opened up a new market over the internet - the download market as download times have been significantly reduced.
The MP3 format is a lossy format. That means that an MP3 file does not contain 100% of the original audio information. Instead, MP3 files use perceptual coding. In other words, that means it removes the information that your ear doesn't notice thereby making the file smaller. The reason lossy formats are used over raw is that raw audio files are too large to travel over the internet at any great speed. By using lossy formats it enables even dial up users to download mp3 files at a reasonable speed. Raw file formats generally require 176,000 bytes per second compared to a lossy format which requires 17,600. The difference is massive and so are the download times.