Adventures In Audio
Avid AudioVision Sound to Picture Editor (part 3)

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.

Thursday January 1, 2004

The Integrated Picture

In case you didn’t know, it’s time to throw away your video cassette
machine, your VHS, U-Matic or Betacam SP, because its time as a post production
tool has come to an end. Now that we have become accustomed to random access
audio from disk, the slow shuttling back and forth of the VCR has become the
limiting factor. Within a year or so, I predict, no-one will be installing new
video equipment for audio post production that doesn’t play back from a
disk (or disc - see A Sound Person’s Guide to Video for further thoughts
on the subject). As you may be aware, Avid are deeply involved in video editing
from disk and they have put their expertise to good use by integrating video
playback into the audio editing system. Video is no longer in a world of its
own, connected only by the slack knicker elastic of timecode. It’s right
in there locked solid to the audio - it even plays back from the same disk!
I haven’t frightened you have I? It used to be considered a wondrous thing
to play back a couple of tracks of audio from a hard disk, but eight channels
and a video picture too must be stretching things a little? But the video isn’t
a full bandwidth picture and therefore imposes only a relatively small extra
load on the system, and remember that Avid have a good deal of experience in
video editing systems that use a much higher resolution picture with four audio
channels so they are well used to getting data off the disk very quickly. Apparently,
if the workload becomes too great, with small segments scattered over the disk
and near simultaneous transitions, then the whole thing will grind to a halt,
which is much better than skipping a segment which may pass unnoticed until
after the session. This is a good point to insert my standard advice which is
to make sure you see the system you intend to buy doing what you will want it
to do in real life. You may be able to buy a mixing console on the basis of
features, performance and a brief trial, but hard disk editing systems are a
very much younger technology and need very thorough testing.

If you take a look at figures 1 and 2, you’ll see the two components
of a typical AudioVision display. If you are familiar with Mac based systems
you’ll know that there are usually a number of windows which you can open
and close as necessary, and move around and resize at will. Having two monitors
isn’t particularly an Avid feature, since you can do this with any Mac
that will take an additional video card. The mouse will roam around both screens
as though they were one work area and you’ll soon wonder however people
used to manage with just one monitor. Looking at what I have chosen to call
the main screen for the moment (Fig 1), the most striking feature is the image
window where you see the picture you are spotting to right next to your audio
work area. Perhaps film dubbing mixers will scoff at this tiny picture compared
to their cinema size projection screens, but you can blow this up to full screen
with a single key press. The audio work area - the Timeline - will at the same
time hop over onto the other monitor so you don’t have to interrupt your
work just to see things a little bigger for a while. I imagine the problem with
using the small window would be scaling the ‘size’ of the sound to
fit the picture, but it is also possible to run a PAL monitor from the system
which can be as big as your budget can afford. As I mentioned earlier the image
is compressed, by a system known as JPEG which stands for Joint Photographic
Expert Group who have developed this as a standard for image compression. I
shall (of course) be covering image compression in the fullness of time in A
Sound Person’s Guide to Video but for now I’ll just tell you that
it is a variable compression ratio system, according to the content of the picture,
with a trade off between image quality and the amount of data taken up. The
picture quality that Avid achieves, considering that it has to be retrieved
from disk at the same time as up to eight tracks of audio, is certainly very
good, although images with finer details will take up more disk space due to
the variable compression ratio. You may have seen moving pictures on a Mac screen
already, produced using Apple’s QuickTime software, and not been impressed.
This works to a much better standard.

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