Audio Description with Control Track

[ghost]

In several European countries, AD is distributed as

• one mono channel with the audio description
• one mono channel with a control signal to drive downstream mixing Details are described in BBC R&D White Paper WHP 198 (2011)

We propose to add labels to the dictionary in 377-41 to support these channels.

Background:

BBC R&D registered MCA labels in smpte-ra as follows: 060e2b34.0401010d.0302010f.00000000 = ch Visually Impaired Narrative Channel 060e2b34.04010101.0d010801.01010100 = ch Audio Description Studio Data Channel 060e2b34.04010101.0d010801.01020000 = sg Audio Description Studio Signal Data Channel

Meanwhile ST 2067-8 also defined '060e2b34.0401010d.03020220.0c000000' = ch Audio Channel VIN

A question that rears its head in this context is whether the AD and the Studio Signal should form part of the same sound-field. An argument could be made that since the control signal should never be routed to a loudspeaker, it therefore should not be part of the sound-filed that contains the audio description. On the other hand, "groups of sound-field groups" suggest that at least in name, the control signal would still be in a "sound-field" so perhaps this is a rather philosophical debate?

[dtatut]

@Ulrich-DPP : if the control signal is transported in an audio channel as if it was PCM data, then it should be treated like an audio channel, even if it does not go directly to a speaker. Many control signals and other kinds of data are transported this way.

[cseidel2]

Brian and I propose adding a MCA Content Value (Table 2 in 377-41) as follows:

Name: "Descriptive Video Control" Symbol: "DVC" Description: "Control signal associated with Descriptive Video to facilitate automated mixing of the program with DV audio."

Note that the term Descriptive Video is used in 377-41 for VIN and Audio Description.

To complete this, our intent is to add the channel and soundfield group names suggested in the comment above to 377-42.

[thomasheritage]

Thanks @Ulrich-DPP there is certainly a use case for this and it would be good for it to be supported.

FYI -- Note that the ULs given above are not entirely correct.

After discussion with Brian and @dtatut, to support this:

• We'll include the Audio Channel Label AudioDescriptionStudioSignalDataChannel and Soundfield Group Label AudioDescriptionStudioSignal in 377-42.
• It looks like we'll then need two new "MCA Content" values in 377-41 -- one value to accompany each of these two Labels. One of these "MCA Content" values could probably be the "DVC" value you've proposed @cseidel2