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Avid AudioVision Sound to Picture Editor (part 3)

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.


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.

By David Mellor Thursday January 1, 2004
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