User manual

433
Synchronization
• Typically, the ASIO control panel for an audio card con-
tains some indication of whether the card receives a proper
sync signal or not, and the sample rate of that signal.
This is a good indication that you have connected the cards and set up
clock sync properly. Check your audio hardware’s documentation for de-
tails.
The only exception to this procedure is if you are using an
external clock – which could be from a digital mixing desk
or special Word Clock synchronizer for example. If so, you
must leave all your ASIO cards in Clock Slave or AutoSync
mode, and make sure that each of them is listening for the
signal coming from the synchronizer, usually passed
through your ADAT cables or Word Clock connectors in a
daisy chain fashion.
VST System Link and latency
The general definition of latency is the amount of time it
takes any system to respond to whatever messages are
sent to it. For example, if your system’s latency is high and
you play VST instruments in real time, you will get a notice-
able delay between when you press a key and when you
hear the sound of the VST instrument. Nowadays, most
ASIO-compatible audio cards are capable of operating
with very low latencies. Also, all VST applications are de-
signed to compensate for latency during playback, making
the playback timing tight.
However, the latency time of a VST System Link network
is the total latency of all the ASIO cards in the system
added together. Therefore it’s extra important to minimize
the latency times for each computer in the network.
Ö The latency does not affect the synchronization – it's
always perfectly in time. But it can affect the time it takes
to send and receive MIDI and audio signals, or make the
system seem sluggish.
To adjust the latency of a system, you adjust the size of the
buffers in the ASIO control panel – the lower the buffer
size, the lower the latency. It's best to keep to fairly low la-
tencies (buffer sizes) if your system can handle it – about
12 ms or less is usually a good idea.
Setting up your software
Now it’s time to set up your programs. The procedures
below describe how to set things up in Cubase; if you are
using another program on the other computer, please re-
fer to its documentation.
Setting the sample rate
The projects in both programs must be set to use the
same sample rate. Select “Project Setup…” from the
Project menu and make sure the sample rate is the same
in both systems.
Streaming digital audio between applications
1. Create input and output busses in both applications
and route these to the digital inputs and outputs.
The number and configuration of the busses depends on your audio hard-
ware and on your needs. If you have a system with eight digital i/o channels
(such as an ADAT connection), you could create several stereo or mono
busses or a surround bus together with a stereo bus, or any combination
you need. The important thing is that you should have the same configura-
tion in both applications – if you have four stereo output busses on com-
puter 1, you want four stereo input busses on computer 2, etc.
2. Set things up so that computer 1 plays back some au-
dio.
You could for example import an audio file and play this back in Cycle
mode.
3. In the Inspector or mixer, make sure the playing audio
channel is routed to one of the digital output busses you
set up.
4. In computer 2, open the mixer and locate the corre-
sponding digital input bus.
The audio being played back should now “appear” in the program run-
ning on computer 2. You should see the input bus level meters moving.
5. Reverse this procedure so that computer 2 plays back
and computer 1 “listens”.
Now you have verified that the digital connection works as
it should.
Ö From this point on in this chapter, we refer to the bus-
ses connected to the digital inputs and outputs as “VST
System Link busses”.
!
It’s very important that one and only one card is the
clock master, otherwise the network cannot function
correctly. Once you have set this up, all the other
cards in the network will take their clock signal from
this card automatically.