Grass Valley Imagestore 750 v.3.0.1 - Manual (Page 159)

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Imagestore 750
User Manual
Note: The AD control tone must be A/B cut (not A/B mixed) so that the control tone always
remains valid.
In both cases, the broadcast consumer will start hearing the AD commentary mix when they
switch from the first to the second stereo pair.
Silence Detection
Note: Silence detection is included as part of the standard audio options (IS-750-Audio6 and
IS-750-Audio16).
Introduction
Silence detection is used to automate control of one or more audio voice-overs based on the
audio level present within the audio source:
• Embedded SDI audio.
• AES inputs.
• Easyplay audio clips (including wide multi-language clips).
When an external audio voice-over can appear at any time (from embedded SDI audio or AES
inputs), silence detection automatically ducks the background and mixes the voice-over. This is
very useful because it removes the need for synchronous automation to control the voice-over.
Easyplay clips that contain multiple language variants most probably have different running
times for each language. With traditional voice-overs, the background for all channels must
remain ducked until the final language completes playing out; which is clearly problematic for
other languages that finished earlier. The silence detection feature gets around this by
detecting the finished language clip and restoring the background audio to its normal level.
Configuration
Follow these steps to add silence detection blocks into an audio configuration:
1 Open the Imagestore 750 Configurator’s ‘Audio Graph’ page.
2 Drag an instance of ‘Audio AutoDuck’ onto the audio graph.
3 Select the number of channels per mixer source (1 to 16).
Note: A maximum of 16 audio channels can be shared between all silence detection blocks.
4 Connect appropriate sources to the background (BG) and voice-over (VO) input pins.
5 Connect appropriate destinations to the output pins.
6 Set the following parameters for the ‘Audio AutoDuck’ block:
Parameter Default Description
Silence threshold –40 Level at which to consider the voice-over input as silent (in dB)
Silence trigger dura-
tion 25 Duration to wait (in fields) with audio below silence threshold
before considering input to be silent
Fade-out rate 25 Fade from duck rate (in fields)
Fade-in rate 2 Fade to duck rate (in fields)
Table 6-7: Imagestore 750 Configurator - Audio AudioDuck parameters