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The Real IBOC Demo

A

autopaint-1

Guest
Here are IBOC samples recorded from a B.A. HD Receptor in the NY suburbs using a dipole 1 foot above floor level for FM and a passive loop for AM reception. These are wav files so they are large but they should give an example of what HD radio sounds like. The samples were recorded on DAT from the headphone jack of the Receptor and transfered to my HD for uploading to Yousendit.

FM Sample; http://www.yousendit.com/transfer.php?action=download&ufid=0AB603B21193169A

AM Sample; http://www.yousendit.com/transfer.php?action=download&ufid=5347EBD848B6C5EE


Tweaking of air chains is still taking place but for those who remember my earlier samples I think you'll hear a big improvement.
 
FM sample says it requires a login.

AM sample sounds a little "grainy" but not as hollow or swishy sounding as I expected. Definitely better than the low-bandwidth satellite channels. Are all AM HD broadcasts in mono?
 
I'll try loading the FM again. I may have to make it a MP3. Actually the AM IBOC can do stereo but at this time most of the stations have mono STL's.
 
autopaint-1 said:
I'll try loading the FM again. I may have to make it a MP3. Actually the AM IBOC can do stereo but at this time most of the stations have mono STL's.
Click to expand...

I think a large percentage of stations, at least in metros, have gone to T1's lately. This means they can do stereo pretty easily, as well as data return and other good stuff.
 
True but for IBOC they really need a linear T. You don't want to mix and match codecs. That's why we are moving from MP2 encoded audio files to wav files on our file servers.
 
The FM sample sounds pretty good. I can still hear some raspiness in the high end but then the 60s source material isn't exactly on the cutting edge of fidelity so it might be in the song, not the signal.
 
autopaint-1 said:
True but for IBOC they really need a linear T. You don't want to mix and match codecs. That's why we are moving from MP2 encoded audio files to wav files on our file servers.
Click to expand...

WHAT the heck is a "linear T" anyway?

A T-1 (or DS1 transmission circuit to be specific) is simply a 1.544 MBit/second DIGITAL transmission 'pipe' that can, if ordered properly from the local Telco, convey ANYTHING you send down it, digitally encoded (A to D converter) of course.

WHATEVER or HOWEVER you encode your linear source (via an encoder) will be sent DIGITALLY to the far end for reconsruction via a 'decoder' (D to A converter with any compression or bit weighting as your 'standard' calls for).

No such thing as a 'linear T'.

(Telecom guy talking here now)
 
Well Mr telecom I won't question you but we in NY call it a linear T when no compression is introduced. In other words rather than compress the data to allow multiple audio streams we feed non compressed data. That wat we don't have a problem introducing multiple codecs causing more artifacts to be introduced. sorr for the comfusion.
 
HD Ready said:
How about we just say a "full T1" to send the audio to its destination, that would be linear (uncompressed) audio.
Click to expand...

Of course, then you get into sample rates and such...a 32KHz sample rate uncompressed will take about 17 time slots on an Intraplex T1 mux, while 44.1 will take up 23.
 
44.1 KHz is default, otherwise you'd need to go through converters if you want to stay in the digital realm.
 
I.B. Iquity said:
44.1 KHz is default, otherwise you'd need to go through converters if you want to stay in the digital realm.
Click to expand...

Pretty much all IBOC systems have rate converters on their input since most STL systems are running at 32kHz sample rates.
 
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