Why will your PC play some video files and not
others? It’s all down to codecs.
So why do we need codecs?
Video uses a lot of storage space on your
For instance 5 minutes of captured camcorder
footage uses about 1gb of storage.
On the plus side, storage is now cheap.
The trouble really comes when trying to distribute
People don’t want to be given hard drives to plug
in to their computer. They want DVDs, iPod
videos, Sky & Freeview.
So the files need compressing to fit these media
...the trouble is that there are hundreds
(thousands?) of compression options!
So let’s start at the top...
Way back in the 1950s three main broadcast
standards were established by various countries:
PAL (in the UK)
NTSC (in the USA)
SECAM (in France)
...and they all worked quite happily for the next
This was mainly because video production was
expensive and made by a small number of
companies. Thus easily regulated.
Then came digital!
The Digital Revolution of the 1990s made video
production cheap and available to the masses.
This made it difficult (impossible?) to regulate.
New digital ‘standards’ were required, and lots of
Instead of being imposed like the 1950 standards,
the new standards were placed in competition with
The theory was that the best standard would
The actual result was a minefield of formats,
containers and codecs...
Codec stands for Code / Decode
It is basically a computer program that en-codes
video to a specified format
From this point on the same codec is needed to
play (decode) the video
The trouble comes when you move your video to
...if that PC/Mac hasn’t got the required codec
installed (to decode the video) then your video
Tip: PC users can try ‘G-Spot’ (freeware) to
identify the codecs used by a video
Oh, and there’s an another pile of codecs for
encoding audio files!
...eh, what about Quicktime and AVI?
Here’s the big confusion: Quicktime, AVI and
Real are not codecs!
These are ‘container’ formats.
This basically means that they contain codec
compressed video and audio in one easy to play
Video codecs can be broadly split into two types:
temporal (or field-based) codecs.
Well known examples are Cinepak
They work by examining and compressing each
frame of video individually.
They have two main disadvantages:
they can be slow to encode
file sizes can be quite large
The best known is MPEG-2 (used for Digital TV &
They watch how much a video clip changes from
frame to frame then compress only the changes
between the first full frame (a keyframe) and the
Thus keeping file sizes down!
parts of the keyframe
The quick answer to this question is to use the
relevant presets within your editing software:
Codecs made Simple in iMovie
But it’s always worth checking with your client
about their requirements.
Especially if they’re planning on showing the video
This is where programs like Apple’s Compressor
come into play (but that’s another presentation for
The ‘i’ and ‘p’ make all the difference!
In terms of picture quality there is very little
between 1080i and 720p:
1080i has a slightly higher resolution but it’s not
very sharp with fast moving action...
...so 720p is favoured by sports networks
1080p is the ideal format but broadcasters are not
yet equipping themselves to transmit in this format
(it takes up too much bandwidth!)
Also known as ‘Full/True High Definition’ or ‘24p’
So it is currently being used as an alternative to
expensive film-stock when actually shooting a TV or
movie film production
These are rival disc formats – they are like super
large DVD discs (holding up to 50gb)
...this means that a HD movie (which obviously
has a larger file size) could fit on one of these
discs rather than span across five DVDs
They are nothing (directly) to do with video
Blu-Ray is supported by Sony,
Panasonic & Apple
HD DVD is supported by Toshiba,
Microsoft & Intel
This could be the next ‘VHS vs
At the other end of the resolution spectrum is the
booming mobile video market
This is more concerned with getting files smaller
to fit on the tiny screen on your phone or iPod
Typical Screen Res is a tiny 176 x 144
Things are moving too fast, the best you can do
is be aware of the issues and make sure you
know the most common settings you work with
And always keep a copy of your finished video
at the highest quality it was produced at!