HD Radio - just what is it and is it really HD?

[Richard]

I just learned about this today by chance. This What I have been able to dig up so far. What I am finding may be an abuse of the term HD just like they did with digital...

NRSC-5 Standard and Reference Documents
http://www.nrscstandards.org/Standards/ ... NRSC-5.asp

DRI8201: Single Chip "HD" Analog Front-End With Radio Baseband
http://www.analogzone.com/hfp_0915.htm

Beyond the integration of HD Radio technology and IF sampled AM/FM, the DRI250 baseband includes audio processing for sound and WMA and MP3 decoders for automotive CD radio. Such integration of digital processing features in a single chip, coupled with TI's new analog front end chip, the DRI8201, results in a lower cost of implementation of HD Radio systems. In addition, as a software radio baseband, the DRI250 allows for several new differentiated features to be added in the future such as surround sound FM for an enhanced listening experience and time buffering for the ability to rewind live radio. TI's programmable solution also allows for the possibility of the Tomorrow Radio Project, a proposal that would allow a second audio stream to be broadcast on each radio station, ultimately giving the listener access to more content on the air. As a software radio, the DRI250 provides manufacturers the flexibility and processing headroom to add support for new standards, features or modifications, as experienced recently with iBiquity's conversion to their proprietary HDC codec.

http://reviews.cnet.com/Polk_Audio_I_So ... 489-2.html

Furthermore, HD Radio makes the same claims of near-CD quality that have rung somewhat hollow in the past with the overly compressed digital streams of satellite radio and MP3.

http://www.rwonline.com/reference-room/ ... es_3.shtml

According to listener testing, conducted by Sheffield Audio Consulting, most listeners could perceive only very small or no difference between audio encoded with HDC at 96 kbps down to 48 kbps. As has been seen in previous digital codec testing, differences were most noticeable in samples of human speech, while music samples tended to survive lower bitrates with less perceptible degradation.

Interestingly, Andrews said, classical music and jazz samples were comparable to 96 kbps quality down to 36 kbps, while voice and rock music samples tended to do poorly at that bitrate. The results suggest that two 48 kbps channels or in some cases a 64/32 kbps split between primary and supplementary audio channels would be appropriate bitrate allocations for a station broadcasting two audio channels.

From the EFF's perspective, the RIAA proposes "a restrictive set of conditions" that would make it difficult for everyday listeners to make convenient fair use recordings of digital radio broadcasts, as they are able to do with analog broadcasts today.

[akirby]

I think that's exactly what they're doing. HD is the buzzword now, not digital.

I heard that AM sounds like FM and FM sounds like a CD. But probably the best feature is multi-casting which would support continuous traffic reports during rush hour or specials, etc. In this case I think the extra content would be worth the bit sacrifice especially if it's still better than what we get for FM today.

[jcrobso]

At this point in time there are no plains for my FM Station to add HD broadcasting.
But tomorrow my boss could call me and say we are.
The amount of processing can be mind boggling.
The sound in the studio is very good, but by the time the signal is send to the transmitter it has been EQd, compressed to within 2db. Digitized, sent over a T1 line, converted back to analog, then to the transmitter.
Until the FCC mandates all car radios have HD capability like they did with FM, it's not going to go very far. john