Chapter 5: File Formats

File formats can be a very complicated discussion, so I'll try to keep it simple.

The main idea is that if you make the filesize smaller, you lose quality - which makes sense, really.

The main filetypes you need to know about are:

Section 1 - Low File Size

FLV (Flash Video) is generally used for streaming video - videos you watch online but don't usually download. The filesize is very small and the quality can be remarkably good for such small files. YouTube uses FLV files for the standard quality videos.

A typical 1 hour FLV video might be 250MB in size (so you could fit 3 on a CD).

Section 2 - Flexible

WMV (Windows Media Video), AVI (Audio Video Interleave), MOV (Quicktime MOVie) and MPEG (Moving Picture Experts Group), also known as MP4 files are all kind of similar. Now there are people out there who will shout at you for saying that and get very irate. And they have a point, because they're all different - but the differences are usually really hard to explain.

They can all be very low quality, small files and they can all be very high quality, large files - or pretty much anywhere in between.

	WMV (Windows Media Video) is the standard filetype used by Windows - so projects you create with Windows Movie Maker or Microsoft Photo Story will generally end up as a WMV file. WMV files aren't that popular with experts because they don't work well on other systems (e.g. Macs or Linux) and aren't always the best quality.

	AVI (Audio Video Interleave) files are very popular. They can be made using different codecs (you might have heard of DivX and XviD, which are popular codecs). A codec is a set of instructions for packaging the video.

	The MOV (Quicktime) file format is owned by Apple, the people who make Macs. The files are generally more popular than WMV files, though, as they still work well on other systems such as Windows and Linux. If you are editing in iMovie then you will probably end up with a MOV file at the end.

	MPEG (or MPG) files are kind of similar to AVI files, because there are several different versions. MPEG1 was used for the original VCDs (Video CDs) which came out before DVDs. MPEG2 was (and still is) used for DVDs and MPEG4 is used for Bluray and also for iPod video files (they are often called MP4 files as well). All of the filetypes mentioned so far use MPEG technology, but that gets quite complicated.

To keep it simple, although all 4 are different - they're also kind of similar, because they're all flexible and can come in very high and very low file sizes, depending on what you want.

File size vary massively, but here are some typical examples:

An hour of video for an iPod might be 400MB
A 1 hour video downloaded for your computer might be 800MB
A 1 hour DVD file might be 4GB (4000MB)

Section 3 - Large Filesize

DV (Digital Video) files are what you get from most camcorders - at least the ones that use tapes. DV footage is absolutely huge, but is a good format to edit with because you don't lose too much quality. You wouldn't want to try downloading DV footage though, because an hour takes up around 13GB (13000MB). iMovie uses DV format by default, and that's why even short video clips need huge project files. You can change your settings to work with much smaller files if you want to, but you will lose some quality and the finished video wouldn't be up to DVD standard.

Reproduced with kind permission from Mark Clarkson, from the originial source