Preparing the Audio for Encoding - A Practical Guide to Video and Audio Compression - page 607

R

L 2 1

3

0

10

over over 20

3

- +

1
3
6
12
18
24
30
42

1
3
6
12
18
24
30
42

VU

Figure 37-9 VU meters.

The meter on the left is the traditional electro-mechanical design. On the right is an
example of the more modern electronic LED bar-graph display.

37.9 Surround-Sound Track Assignments

If everything you have done so far has been carried out carefully, it will not be necessary
to remap the surround-sound tracks. But if you arbitrarily ingested them without any
automatic track assignment, you should check that the sound is associated with the appro-
priate channels. Pairs of channels must be grouped so that the encoder deals with several
alternative stereo pairs.
Modern coding systems should be aware of the 5- and 6-channel surround-sound
systems and ought to do a lot of this automatically for you. Some ingest processes allow
for only two channels of audio to be ingested at a time, and it is such systems that often
necessitate this fix-up stage.
Mono and stereo audio would be presented as shown in Figure 37-10.
Surround and other multi-speaker systems look more similar to Figure 37-11.
Theater systems have many more surround speakers, although they may not all be
driven independently. The highest specification for theaters is the Lucasfilm THX system,
which must be calibrated and tested by Lucasfilm engineers before the THX badge can be
put up on the wall.