The CBS Dolby setup utilizes a Dolby 572 Dolby-E decoder to extract the stereo or network 5.1 audio. I also route our upconverted audio through this decoder which goes into PCM bypass when non Dolby-E audio is detected.
The 572 feeds either the two channel stereo or the six channel 5.1 to the Dolby 569 audio encoder. The 572 decoder is locked to house sync. The output of the 569 encoder is fed to the HD encoder which is also locked to house sync. The CBS setup states to set the reference source for the 569 to the input audio bitstream.
I ran a separate DARS (digital audio reference signal) from our house sync generator (which is locked to the GPS satellites) to the 569, and set its reference to this external source. This forces the 569 Dolby audio encoder to be locked with the Tandberg HD encoder. This absolute lock of the two fixed the dropout issue.
In a nutshell, the CBS station has to run a stable external audio reference to the 569 encoder, deviating from the CBS suggested setup.
NBC does not utilize a separate decoder at all, their IRD supplies all of the audio channels. They only use the Dolby 569 and it is locked to an external reference. The ABC system utilizes a different Dolby decoder and their 569 feeds an audio frame sync. (at least this is what the Dolby site says, Warren help me out here).
This problem with the Mits and Dish Tivo receivers has been bugging me from the beginning and I was determined to get it resolved. Sorry It took so long. We have been quite busy at the station and I had to peck at it whenever I had some time.
Thanks for your patience.
Assistant Chief Engineer