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 PC/Mac.

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 the footage.

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 thirty years!

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 options competed...

Instead of being imposed like the 1950 standards, the new standards were placed in competition with each other.

The theory was that the best standard would become dominant.

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 another computer...

...if that PC/Mac hasn’t got the required codec installed (to decode the video) then your video won’t play.

Tip: PC users can try ‘G-Spot’ (freeware) to identify the codecs used by a video

Sorenson Indeo Cinepak

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 file.

Video codecs can be broadly split into two types:

frame-based codecs temporal (or field-based) codecs.

Say What!?!

Well known examples are Cinepak and Motion-JPEG

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

=Tim

e

The best known is MPEG-2 (used for Digital TV & DVDs)

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 next.

Thus keeping file sizes down!

=+++

Keyframe

=+++

Copies unchanged 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 overseas.

This is where programs like Apple’s Compressor come into play (but that’s another presentation for another day!)

Interlaced Progressive

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 formats

Blu-Ray is supported by Sony, Panasonic & Apple

HD DVD is supported by Toshiba, Microsoft & Intel

This could be the next ‘VHS vs Betamax’

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

You can’t!

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!

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