BSO on the radio - not for me anymore

Aaron Read
Thu Oct 14 13:47:41 EDT 2010

I have a vague...very vague...recollection that WGBH was splitting the
HD1 and HD2 evenly for 48kbps per channel.  But that was from a while
back; no idea if it's still true...or ever was true in the first

However, I should point something out here: the HDC codec (itself a
thinly-disguised AAC codec) is rather programming & processing
dependent in terms of perceived fidelity vs. bitrate.   I have heard
samples at 24kbps that sounded better than some stations at 96kbps
because they've put in the right pre-processing and regular
processing.  FWIW, the codec does has its limitations, though.  For
example, generally HDC sounds better on music than on talk because
richer dynamics of music provides more places for the psychoacoustic
algorithm to dump bits without there being an audible penalty.
Similarly, female voices can sound very sibilant on HDC if you get the
pre-processing's just a quirk of the codec.

And I gotta say, pre-processing does make a HELL of a difference.
This summer our Omnia 6 FMHD on WEOS had a muffin fan die, so I had to
put in a spare Omnia 3FM and I couldn't use our Neural Audio
preprocessor the same way.  The difference was night and day; without
the proper pre-processing from our Neural, the HD sounded like a
"decent MP3 stream" at best; a lot of crunchiness and swishiness
sounds.  When I got the 6 back in with the Neural, our HD went back to
sounding rich and full again and all the crunchiness/swishiness
disappeared.  It helps that we don't multicast so I have the full
96kbps to play with.  But if done right, you can get comparable
results down to 32 and even 24kbps with the right programming.

Off the top of my head I don't know how well classical music
inherently fares on HDC, nor do I know what WGBH is doing in their
processing chain...and I don't currently live close enough to listen
myself.  I would assume that, given WGBH's reputation, they'd put some
time and effort in to making their HD2 sound as good as it can.  The
upshot here is that, theoretically, the all-classical HD2 should have
comparable fidelity to the old analog setup.  Possibly even better
since there's better frequency response (out to 20kHz) and no
multipath or similar interference issues that affect audio fidelity.

Aaron Read
General Manager
WHWS 105.7FM
(315) 781-3811

And indeed, 89.7 HD2 [line of sight] is probably my only answer for
BSO on the radio.  [No, I can't put my dipole in the attic].  Being
clueless about the variations on the HD theme, is HD2 the same or
lower quality [bitrate] than HD1?  Or will that vary depending on the
station [WGBH in this case]?
    Thanks - George

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