7th Sense Delta Benutzerhandbuch - Seite 11

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Timing Sources

Chasing LTC

Multiple Delta servers that are not master-slave related, or are in different master-slave timing groups,

and systems incorporating other devices, or control desks, will need more than a Delta timeline timing

packet, so instead we can use a common timing source of linear timecode (LTC), in an audio stream.

This could be played as an audio track on one Delta server, but it must be accommodated within the

specification of the server providing the LTC stream, since it requires media storage capacity,

bandwidth, and an audio channel. One audio channel of this server is assigned to LTC output, and this

channel can be played through an alternative audio device (typically motherboard ASIO audio), with the

show audio output running a more professional quality device. This prevents cross-talk and accidental

playing of the LTC as show media. The arrangement expands the synchronisation possibilities, but the

system as a whole is still vulnerable to dependency on the one server. An LTC-chasing server similarly

requires a separate ASIO LTC audio input, which must be accommodated in the server specification if it

also requires audio output.

An alternative solution is to take the LTC source from a generator app, or use a purpose-made audio

track, played on a dedicated server, connected by direct audio input, or SMPTE device such as Adrielec,

or an SDI card.

By switching Delta timelines to listen to this LTC source instead of master server timing packets, their

playheads will track the position dictated by the LTC source (their new 'master'). Set the LTC to run, and

the Delta LTC-chasing playheads follow with a configurable pre-roll time. Delta has an LTC reader

(7thLTCReader

) that converts the analogue audio signal into digital format SMPTE code, and which

free-runs for a number of frames to cover any transient loss from the TLC source. (An Adrielec or similar

card will do the same thing as the LTC reader.)

Synchroni s i ng Del ta Medi a Sys tems