Image Processing Reference
In-Depth Information
Figure 29-8 BMD Workgroup Videohub. Source: courtesy of Blackmagic Design.
Although you may want to route audio and video separately sometimes, you will
probably want to switch them together so that they are routed to the same place most of the
time. On a very big matrix, you will have a video layer plus two audio layers, and if you
are providing surround sound, you might potentially require five or even seven layers of
audio switching along with the video. This gets quite expensive, and the control system
increases in complexity accordingly.
Embedding Audio Versus Separately Routed Audio
A very neat solution to the massive wiring costs in a big studio is to embed the audio
inside the video signal, thereby removing the need for more than one layer in the switcher.
This allows economies in cabling systems and also reduces the number of fiberoptic links
you need to provide. Embedders and de-embedders should be placed adjacent to where
the audio and video need to be processed separately.
Modern SDI video cards such as the AJA Kona and the Blackmagic Design DeckLink
products support audio embedding within the driver that feeds the outputs of the card.
The audio your equipment is compatible with might be in digital AES format, or if
it is analog, it is likely to be balanced audio. You will need to convert back and forth,
so some AV glue ware will be necessary. This sort of I/O conversion is available from com-
panies such as Vistek or Miranda. There are many others as well.
Loop Back
When you wire your studio, there are times when you will need to test something. Putting
in a few extra circuits and leaving them unconnected is a good idea. Use these for loop-back
Vistek Electronics Ltd: http://www.vistek.tvt/
Miranda Technologies Inc.:
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