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OmniTek XR User Guide, Software Release 2.3 Page 99
Configure Filter
Calls up the dialogue through which items for display and/or logging are selected (see
page 119).
Look & Feel
Calls up the Look & Feel dialogue used to set display parameters across the whole
application (see page 59).
Reset options
These options reset different aspects of the Audio Status display.
Enable columns
This option displays a dialogue through which you can select which details are displayed
in the Audio Status window.
Dolby Frame Data (where supported)
The inclusion of Dolby-encoded audio within PCM channels takes advantage of the
facility of the AES3 serial digital audio interface to transport non-PCM data.
The Dolby-E data is made up of metadata detailing how the coded audio is to be handled
and metering information. It is delivered in bursts of ‘Dolby frames’. One Dolby frame is
associated with each video frame.
The format of the data is defined by the SMPTE 337M standard. This specifies a header
containing information about the data – in this case, defining the data both as non-PCM
data (as required by the AES3 interface specification) and as Dolby-E data. (The SMPTE
337M standard caters for a range of different non-PCM data types that could be added to
the audio channels.) This header is then followed by frames of Dolby-E data, each
starting with synchronization segment followed by metadata, coded audio data and
metering information. This gives rise to the following packet structure.
SMPTE
Preamble
Dolby E Frame Dolby E Frame Dolby E Frame
Sync. Segment
Audio Segment Audio Extension *
Meter
Segment
Metadata
Segment
Metadata
Extension *
* Low frame rates only
This structure can be implemented at a bit depth of 16, 20 or 24 bits, depending on the
total amount of data that is to be transferred.
A key requirement on the transport of Dolby data is that it transported synchronously with
the video in order to provide exact matching between Dolby-E frames and video frames.
It is also necessary to be able to edit Dolby-E audio and to cross-fade between Dolby-E
streams without introducing any glitches or other artefacts.
Such switches and edits take a number of video lines to complete, so in order to prevent
such edits and switches interfering with the Dolby data, the Dolby standard defines a
reference position within a video frame after which the Dolby frame should start. This
provides a ‘guard band’ between successive Dolby Frames during which edits and
switches can occur without affecting the integrity of the Dolby data. The width of this
guard band is further extended by ensuring that there is a gap between the end of the
Dolby frame and the end of the video frame.