Grass Valley Imagestore 750 v.3.0.1 - Manual (Page 157)

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Imagestore 750
User Manual
program, describing what is happening on the screen during the natural pauses in the audio,
and sometimes during dialogue if it is deemed necessary.
When the viewer hears the television program, the original program audio track is mixed with
this additional narration or commentary. The mixing can be done at one of two places in the TV
signal chain:
• AD receiver mix.
• AD broadcast mix.
AD Receiver Mix
Program audio is mixed with the mono AD commentary in each TV receiver. The viewer can
adjust the AD commentary level at their own receiver. Mixing is performed under the control of
a special control tone signal, which can be passed as an audio signal through television equip-
ment for transmission. In this mode, both the original program audio and AD tracks (mono
commentary and control tone) are broadcast.
Note: No special Imagestore 750 option is needed in this case because the control tone signal
and the extra audio commentary track can both be passed as ordinary audio signals through
the Imagestore 750.
AD Broadcast Mix
Program audio is mixed in with the AD commentary at the TV station ready for transmission.
Mixing is again performed under the control of a special control tone signal, but this time it is
done by the Imagestore 750 ahead of transmission. In this mode, both the original program
audio and program-with-commentary are broadcast.
A mono commentary track is mixed by Imagestore 750 with stereo background audio to yield
an extra program-audio stereo track with the commentary mixed in. The mixing of the commen-
tary track is (again) controlled by a special control tone from another audio channel. The control
tone determines how the background audio is ducked and the commentary mixed with it.
Note: The IS-750-AD option is required in this case.
Product Code
The code for the Imagestore 750’s audio description is IS-750-AD. It represents one AD block
only.
Note: This is a software option which does not require any hardware upgrade.
The complete set of Imagestore 750 product codes is listed in Chapter 11.
Configuration
After the audio description option has been purchased and installed, a single ‘Audio Descrip-
tion’ block becomes selectable within the Imagestore 750 Configurator’s ‘Audio Graph’. You can
place this block in your audio configurations as required.