Choosing the Right Codec - A Practical Guide to Video and Audio Compression - page 172

Table 8-1 Codec Categories

Property Production codec Delivery codec

Compression ratio Low - typically 4:1 High - typically 50:1 or better.

Quality Perfect Good but may degenerate down to

sub-VHS quality.

Lossy Zero for some codecs, for Very

others it is very minimal.

Bit rate 25 to 50 Mbps Down to 800 Kbps for video and

24 Kbps or less for audio.

File size 20 GB per hour Down to 0.4 GB per hour

Editable Yes Not really

Compositable Yes Only with alpha channel data

provided and as an overlay at best.

Key frames only Usually Almost never.

Conversion to other Easy Further significant degradation

formats likely.

content so that it can fit in the finite space of a CD or it can be transmitted through a broad-
band network. This kind of compression is somewhat lossy or even on occasion very lossy.
These codecs would be grouped under the category known as delivery codecs. Table 8-1
summarizes the attributes of these codecs.
Most of the discussion in this chapter relates to choosing a suitable delivery codec. You
don't have the same choices available when looking at production codecs since these are dic-
tated by the infrastructure of your studio or the equipment you already have installed.

Try several different manufacturers' codecs to see whether one suits your
content better than another.

8.3 Why Are Standards So Important?

Many different codecs have been invented. They tend to be based around similar algo-
rithmic approaches because the engineers all go to the same conferences and read the same
technical papers. The differences are in the fine points of the implementations and the
choices the engineers make when constructing them.