Grass Valley iTX System v.2.6 - Manual (Page 203)

Configuring the audio output for a playout channel
Output-channel limit
An Output Server can play out multiple audio tracks in different formats. The number of tracks
and their formatting depend on the channel configuration. The total number of channels in all
output tracks cannot be greater than 16. This limit is set by the SDI standard.
If your channel is running on Output Server 2, see Output Server 2 Channel Configuration Guide.
Encoded-data formats for playout
iTX can handle audio content in any of three encoded-data formats:
• PCM, uncompressed digital audio.
• Dolby D, compressed data.
• Dolby E, compressed data.
To mix or overlay audio sources (for transitions or voiceovers), iTX requires the content to be in
PCM format. This means it must decode any Dolby E or Dolby D data before it can work with it.
After processing the content, it may re-encode it for delivery in either of these formats. For
such functionality to be available, your system requires specific iTX Licenses.
Sometimes, an item of media has multiple audio tracks with content in more than one of the
accepted formats. In each track there are usually a number of channels to carry the audio
information.
A PCM track can contain 1, 2, 4, 6, 8 or 16 channels. These may be mono, stereo pairs or
discrete surround-sound channels.
A Dolby D track has 2 channels to carry the compressed data. This data, when it is decoded and
converted into analogue form, may produce 6 channels of 5.1 surround-sound content and a
pair of stereo channels (sometimes called a stereo downmix).
A Dolby E track has 2 channels of compressed data. The data produces 6 channels of 5.1
surround-sound content; or 6 channels of 5.1 surround-sound content with 2 other channels;
or 2 pairs of stereo channels, in which there is silence on the second pair.
We sometimes use this shorthand notation to refer to the Dolby Digital channel formats:
• AC-3 3/2 for the 5.1 surround-sound channels.
• AC-3 2.0 for the stereo pair.
The Media Watcher operation is controlled by a configuration option – more details , page 88.
Configuring the audio output of an Output Server
To configure an Output Server to embed one or more audio tracks in its SDI output signal, you
specify the output requirements. iTX then uses the available sources to produce the required
output.
In selecting which source track(s) to use, it follows a set of rules. (See later in this section, "How
iTX determines which source track to use for the output" on page 209.)
For the configuration, you use the Audio Mapping panel on the Channel Configuration pop-up
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March 2015 System Administrator Guide Page 203 of 404