Adding AoIP to Existing Facilities

At this year’s NAB Show, I was engaged in a discussion about audio over IP with Phil Wagner, recently named president of Apogee, when he mentioned that no one was really discussing how to merge the technology into existing television environments. My own columns have been pointed more toward implementing it into new builds.


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There are really just a few key things to keep in mind when tossing AoIP equipment into the technology mix of a current broadcast plant, but with SMPTE ST-2110-based facilities coming online and AoIP beginning to manifest itself in a very physical sense, this seems like a good time to look at them.

Just as we’ve done since television audio became digital, everything in the plant needs to be referenced to the same master clock. This has traditionally meant providing either black, tri-level, word clock or AES reference (DARS), but network connected devices—surprise—look for their clock on the network, which means we now need to provide them with an IEEE 1588 Precision Time Protocol (PTP) clock, which has been referenced to the house master. In the past this might have been achieved with a master clock from the IT world, but broadcast device manufacturers now provide master sync generators that include PTP alongside standard reference signals. Reference remains critical because the audio going through those network cables is still digital, so nasty tics, pops or complete lack of audio is the result when the reference clock is missing or incorrect.


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