OmniTek 2.3 manual Dolby Frame Data where supported, Configure Filter

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.

Dolby E Frame

Dolby E Frame

Dolby E Frame

SMPTE Preamble

Sync. Segment

Metadata Segment

Audio Segment

Metadata Extension *

Audio Extension *	Meter
	Segment
* 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.

OmniTek XR User Guide, Software Release 2.3 Page 99