Video Files & Editing

Raw video files are often huge (e.g. 1 hour of Digital Camcorder video footage occupies ~10 Gigabytes of space). For many webusers downloading large media files is not an option.

The reason why video files are so Huge is pretty simple

Like film video cameras (and other capture devices) shoot a series of still frames in rapid succession (30 frames per second (fps) is what most video cameras operate at) to give the impression of motion. Even just 15 second video of 320 x 240 resolution at 15 fps shot on a digital camera occupies 4Mb of space.

However fear not there are some solutions to size problem.

Firstly you can decrease the size of the clip (either in length or decreasing the resolution). Like images video clips are often talked about in resolution terms e.g. 640x480. If you reduce the resolution you can reduce the size of files like theses 2 stills

Franz Josef Glacier March 2003 JPEG
80% compression 320 x 240 = 10Kb

Same picture JPEG
120x90 at 80% compression
= <2.5Kb

Secondly you can "compress" the video footage. Most video file forms allow for some form of compression. This is not a million miles removed from the techniques used to compress still images . However the more you compress the more degradation you get. Loss of colour and sound can help decrease file size too!

Thirdly you can drop the frame rate. However below 15 fps and motion starts to appear jerky

Finally you can stream your video. Unlike normal video files which need to be downloaded before being played, with streamed media you see video on-demand (i.e.. it plays as it downloads). Essentially you download part of the file to act as a buffer. Once you start playing from the buffer, the file continues to download topping up the buffer (think of a sink or a bath that you've partly filled. If you pull the plug out and turn on the tap with a bit of tweaking you can hopefully keep the water level (i.e. buffer) the same). However you may need a special server to stream your media from. We have whole tutorial segment devoted to streamed media with example files.

Most video editing programs are geared to making web clips and will do at least the first 3 tasks for you (many will also create streaming media ready files too!!). Many are supplied with video capture devices or cameras as part of bundle. A free example is windows movie maker which is bundled with windows ME and XP. It is biased towards .wmv file format. We have a quick guide to using it.

Lets now look at video file types commonly used on the web

.avi

Short for audio/video interleaved. Originally developed as a rival to Quicktime format for Windows machines but will be playable on most computers via helpers and plug ins. It can use several compression schemes and is becoming increasingly popular. Most digital video cameras shoot in .avi format

mouse .avi file (66Kb)

.mov

These file types are based on the Quicktime (QT) system. Its designed initially for the Mac platform but is now usable via a plugin and helper application on most other operating systems. You can load the standard quicktime player™ from Apple for free as well as get access to a host of resources. QT has some great compression schemes which often make QT files smaller without loss of quality.

It can also be streamed

Georgia the cat .mov (190Kb)

.mpeg

This format takes it's name from the developing group (motion Pictures Expert Group). Remains an important web video file type due to the range of compression that can be applied. Unlike avi and Qucktime not developed for a particular operating system
http://www.mpeg.org/ can provide more info

.wmv

Windows Media Video.
Part of Microsoft's windows media format, a comparatively new all singing and dancing media format but as you can guess has Microsoft's resources behind it. It benefits from jumps in compression technology and has the weight of Microsoft behind it. WMV files can be downloaded or streamed. Microsoft have tons of resources at http://www.microsoft.com/windows/windowsmedia/default.asp many of which are free to download.

Franz Josef Glacier low quality .wmv file (90KB)
Franz Josef Glacier higher quality .wmv file(190KB)

.wmv files can also be streamed

.rm

RealVideo® files.
These are the archetypial streamed video files. Good examples can be seen in action on the BBC news site at http://news.bbc.co.uk/). One of the first and still most popular streamed media format. The basic player can still be downloaded for free at http://www.real.com/. You can also use the files as non streamed format, but they are not so well designed for that

But for more details about creating .rm files visit the Real networks site at http://www.realnetworks.com/ they have a host of free resources. We have 2 streamed examples on this site

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