User Manual

Preparing the Hardware for Capture
166
Digital Audio Input
Digital audio inputs (ADAT, AES/EBU, S/PDIF, and SDI Embedded Audio) provide their own
timing reference. If sample rate conversion is not available on your system, or you have
disallowed it by selecting “Never” in the Input tab of the Audio Project settings, no other
connections are required to achieve sync, so long as the source deck is genlocked.
c
When using the AES/EBU inputs, your system uses the lowest numbered channel that is
enabled for input in either the Capture tool or the Audio tool as the timing reference. When
sample rate conversion is not in use, it is important that you lock all AES/EBU inputs that
are used simultaneously to the same timing reference.
If the digital media sample rate is different from the project sample rate, and sample rate
conversion is available on your system, and you have allowed sample rate conversion by
selecting “When Needed” in the Input tab of the Audio Project settings, then sample rate
conversion is running in your Avid input/output hardware. In this case, the output of the sample
rate conversion uses a sync source under the same rules described above for analog capture.
c
If you need to synchronize audio with video clips captured separately, Avid recommends
that you connect a sync source to both your Avid input/output hardware and the audio
deck to prevent drifting of the audio during editing, even when capturing digitally. This
will ensure synchronization even if sample rate conversion is required.
If sample rate conversion is available on your system, the background color of the I (IN) button
in the Audio Tool informs you of the status of each digital input. If the background color is
yellow, the input is not connected (no valid clock is detected). If the background is blue, the input
is valid and no sample rate conversion is in use. If the background is green, the input is valid but
a sample rate converter is in use. If you mouse over the I button, a reminder of how to interpret
the color appears.
For more information about sample rate conversion, see “Selecting the Audio Sample Rate and
Controlling Audio Sample Rate Conversion” on page 199 and “Audio Sample Rate Conversion”
on page 834.
c
When using the AES/EBU inputs, if channels 1 and 2 do not require sample rate
conversion, none of the other inputs have sample rate conversion applied. However, if
channels 1 and 2 are not in use, you can convert higher numbered channels to match the
rate of the lowest numbered channel, if the Audio Project settings allow sample rate
conversion.