The world of digital video is full of strange names, numbers and abbreviations. Things like ‘mpeg’, ‘avi’, ‘mov’ and ‘m4v’. Then there are numbers like 1080i or 720p.
What do they all mean and which ones do you need to know?
Film formats.
When movie film first came out it also came with a set of numbers, 16mm, 8mm and 35mm. These were pretty easy as they referred to the width of the actual film. Home movies were shot mainly on 8mm with 16mm for TV and 35mm for feature films.
Video
When the first analogue video recorders came onto the market there was VHS and Betamax, then S-VHS, etc. However once video moved into the digital world the acronyms and abbreviations multiplied over and over and every day it seems, someone comes up with a new format and/or encoding system for digital video.
Encoding/Decoding (‘Codec’ for short)
To record and then play back a digital image, whether its a still image or a video, the image has to be converted or ‘encoded’ into data.
The challenge in doing this, is on the one hand, maintaining a quality image that is watchable while on the other hand, ensuring the size of the finished file is not too large.
Video chews up data. A single still image taken with a smart phone is around 1.5mb in size. There are 25 still images per second in video, so 30 secs of video could potentially produce a file that is 30 x 1.5 x 25 = 1,125mb or 1.25gb, which is huge.
The codec – all done with mirrors
This is what all those letters and numbers are for. They describe all the various codecs computer companies, camera manufacturers and software developers have come up with to reduce the file size of a video recording, while still maintaining a quality image.
This means that the above example of 30 secs of video can be reduced to 100mb or less, depending on how it is ‘encoded’ (or converted to digital information) when it is shot and then ‘decoded’ when you watch it.
Video is different from film
When you shot with film, apart from aperture, focus and lens settings there was nothing else to really adjust. You shot the footage, developed it and that was it. There were some chemical tricks you could use to ‘pull’ or ‘push’ the exposure in the developing process but not much else.
In digital video, everything is adjustable, in the camera, the editing system and in how it’s viewed. That’s what all those letters and numbers refer to, the codec used to encode a piece of video together with the height of the image in pixels (1080, 720 etc)
There are lots of articles on the various codecs in use. (This one on Wikipedia is very scary – too much information).
So what do you need to know?
1. Work backwards from your end product. How is your video going to be seen? Home movie? On the web? DVD for a client? TV show or even a cinema release?
2. Always shoot at the highest quality you can and do the conversion down to the smaller file size in post-production.
3. Whilst there are lots of codec options, there are some common ones. YouTube, for example, lists its preferred ones on their web site.
4. Your camera and editing system will have their own native formats. DSLR cameras shoot images that are 1920 x 1080 in size. (Width by height in pixels). Generally the image is compressed using the H.264 compressor. (Note that this compressor may not be ideal for editing, so you need need to convert this to another codec.)
A quick primer
1080i – usually refers to a high definition digital image for TV
720p – a high quality digital image, suitable for the high definition web usage and TV
MPEG 4 or mp4 – this is a codec designed for web streaming
.mov – this is a Mac based codec and is widely used
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