Image Processing Reference
In-Depth Information
Table 8-1 Codec Categories
Production codec
Delivery codec
Compression ratio
Low - typically 4:1
High - typically 50:1 or better.
Good but may degenerate down to
sub-VHS quality.
Zero for some codecs, for
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
Not really
Only with alpha channel data
provided and as an overlay at best.
Key frames only
Almost never.
Conversion to other
Further significant degradation
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.
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.
Search WWH ::

Custom Search