Delay on WODS-HD3

[Aaron Read]

 >> Can the delay be partly explained by the receiver itself?
 >>

In theory, no.  The HD signal's audio component is supposed to decoded 
as one entire package.

However, I suppose an audio stream with a different bitrate (say, 24kbps 
vs. 48kbps) could very well require more/less processor cycles to decode 
into audio.  I don't know if the rest of the streams are delayed to 
accommodate that, but I would assume they aren't.

Also, I have no idea if an audio stream in the 24kbps of extended hybrid 
mode is decoded at the same time an audio stream within the 96kbps of 
the main channel.  Logically, again, I would suppose there isn't any 
special synchronization there...but I wouldn't bank too much on my 
assumptions.

One of these days I'll get around to reading "The IBOC Handbook"; if 
there's any clues to the answers for these questions...they're probably 
in there.  But it's entirely possible there simply are no answers to 
these particular questions, because a lot of the encoding algorithm is 
"black box"; not part of the standard and well-hidden by iBiquity's patents.

- Aaron

P.S. To be clear: HD Radio receivers DO impose a slight delay in 
decoding overall, and every radio (not just every model, I mean every 
single radio) is different.  You can hear it yourself by tuning an 
analog radio, and three different HD Radio receivers, all to the same 
HD-enabled station.  Even if the analog/digital audio is perfectly 
time-sync'd, you'll hear all four radios be slightly out of sync with 
each other...and the HD Radios will all be slightly more delayed than 
the analog.

The question, however, was where the extra 30-odd seconds of delay that 
multicast channels have is coming from.  That's a (presumably) different 
story.

-- 
----------------------------------------------------------------
Aaron Read                  |  Finger Lakes Public Radio
friedbagels@gmail.com       |  General Manager (WEOS & WHWS-LP)
Geneva, NY 14456            |  www.weos.org / www.whws.fm