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Stereo on HD3!
- Thread starter Eli Polonsky
- Start date
Do you still have to pay iBiquity a fee if you run a non-com, like NOAA Weather Radio on your HD3 feed?
Note that with the HD radio codec which is based on AAC++, that stereo does not use anywhere near double the bandwidth of mono. So for a 32 kpbs stereo channel, using Parametric Stereo, perhaps only 2 to 4 kbps can be dedicated to the stereo (L-R) information. Using a 32kHz sample rate on the 32 kpbs channel which gives about a 16kHz audio bandwidth can further improve the codec efficiency. Coupled with a well selected audio processing algoritm (with a 15 kHz audio brick wall roll-off) this can produce a surprisingly good sound.
As mentioned earlier the extened hybrid mode can allow up to an additional 48kpbs of bandwidth. So three 48kbps reasonably high quality channels are possibile. Not sure how many stations use the full extended hybrid mode yet, which has 3 configurations if I remember correctly.
As mentioned earlier the extened hybrid mode can allow up to an additional 48kpbs of bandwidth. So three 48kbps reasonably high quality channels are possibile. Not sure how many stations use the full extended hybrid mode yet, which has 3 configurations if I remember correctly.
HD Radio's codec is not based on AAC+... at least not officially. iBiquity calls it "HDC" (HD Radio Codec?) and just says that it's proprietary. They did license SBR (Spectral Band Replication) "fake treble", but not the full AAC+ codec. It does not appear to use Parametric Stereo, and its real-world performance is not as good as AAC+ is at equal bitrates.
I'm still streaming my HD-4 for you to listen to, but bad news.... its all Christmas
This is encoded at 24kbps in Stereo for the Importer (HD-4 Broadcast)
and your listening on-line @ 128kbps AAC+ (by means of a Sangean HDT-1 HD Receiver connected to the Streaming Audio Computer)
http://69.95.45.82:2000/listen.pls
This is encoded at 24kbps in Stereo for the Importer (HD-4 Broadcast)
and your listening on-line @ 128kbps AAC+ (by means of a Sangean HDT-1 HD Receiver connected to the Streaming Audio Computer)
http://69.95.45.82:2000/listen.pls
RadioEngnr said:
For a 24 kbps HD-4 .. Sounds pretty dang good... "I'm dreaming of a White Christmas" (I am hearing at 7:16 am eastern) sounds a little "swishy" (some artifacts) in parts but overall for 24 kbps the audio is pretty darn decent. [This is the first I've heard any off air HD].
Very impressed with the stereo separation; Dino's wide stereo 60's 'Let It Snow' had superb stereo imaging - better than Sirius or XM's standard 32Kb bitrate music stations, and now that XM is dumbing down music stations to 24Kb mono, it's too bad that SXM's 24Kb couldn't have your stereo separation. Good decoding on the Sangean HD1X tuner too. Do you do any additional audio processing from the HD tuner to your internet streaming device?
Also, are you using the 'expanded' HD-FM setup with a larger bandwidth than standard?
Based on your quality of a stereo HD-4, I don't know why AM stations wouldn't run stereo audio on one or two HD-4's i their market, heck, even HD-3's in order to increase coverage. Again, it's back to providing a good product and getting the tuners in 50% of the cars.
Also, are you using the 'expanded' HD-FM setup with a larger bandwidth than standard?
Based on your quality of a stereo HD-4, I don't know why AM stations wouldn't run stereo audio on one or two HD-4's i their market, heck, even HD-3's in order to increase coverage. Again, it's back to providing a good product and getting the tuners in 50% of the cars.
I am using Parametric Stereo on the iBiquity Importer
Some of the songs that are in the Christmas Library are not really high quality, so your hearing the artifacts from the source material
there is no EQ from the Sangean to the Streaming Computer, nor is there any conditioning being done inside of the Streaming Computer.
Actually it sounds much better in your car than on-line
My HD-3's sound better than this HD-4, I will stream one of them in a few days,
I have spent many, many hours tweaking the processing too
Some of the songs that are in the Christmas Library are not really high quality, so your hearing the artifacts from the source material
there is no EQ from the Sangean to the Streaming Computer, nor is there any conditioning being done inside of the Streaming Computer.
Actually it sounds much better in your car than on-line
My HD-3's sound better than this HD-4, I will stream one of them in a few days,
I have spent many, many hours tweaking the processing too
Finely tuned audio processing can help make the most of any digitally compressed medium (HD Radio, Internet streaming, DAB, DRM, etc.), but most HD stations (at least on FM) are using identical processing settings for both analog and digital, in order to make the blend back and forth between analog and HD1 less noticeable and annoying. So in that case you get all of the digital compression artifacts with none of the benefits of not having a pre-emphasis curve to deal with!
satech said:
You'd think they would optimize the processing to get as good an HD sound as possible so when your radio has HD kick in there is a WOW factor and an immediate benefit of having paid more for an HD radio.
Otherwise why don't FM stations have all mono audio so when your radio switches from stereo to mono it would be less noticeable and annoying?
Not bagging on you satech (don't even think that
) just this whole "HD is so much better than analog even though we make it sound just like analog so you won't be disturbed by or notice the difference. But WOW there is a difference but you won't notice it so it bugs you."I'll end now before I go too MPFC.
Yes, but in fringe signal areas, HD car radios are switching between analog and digital so often that it gets very annoying to hear the audio suddenly get much brighter every time the HD kicks in. In a car where you're never sitting in the "sweet spot" of the stereo imaging anyway, a change in tonal balance is much more noticeable than a change in stereo separation, as with analog FM blending between stereo and mono.ajc_trw said:
ai4i said:
I take it that you don't live in semi rural areas? True, most city dwellers do listen within the protected contour, although there are a lot of rim shots out there. For those of us who live outside of a top 50 market, almost everything can be a DX catch. Even people who live in large spread out markets like LA or DFW experience it.
Here in a Top 100 market, a 7KW 12 miles south of the city makes the "ST" light flicker throughout most of the city and on the HD a flip from analog to digital about 3 times just while sitting at a traffic light!
When this station does live remotes they turn off the analog delay, so you hear the same thing said over again and again as it toggles back and forth instead of using a VHF cue channel, they monitor off-air, so it's a big cluster on the weekends and until they remember to reset the HD analog delay and sync it up again. Not a good example. This is a station that could benefit from the full allotted HD power, IMO.
The same group also has a 50KW FM with HD, but it doesn't even have active PAD data or even RDS, yet alone an HD2. Sad.
The engineer for their group is more an I.T. guy and he just gets pissed when I suggest improvements to his group of stations he's responsible for; just doing the minimum to get by and that's it. And don't get me started on how their AM is in shambles with STAs for the past 5 years.
When this station does live remotes they turn off the analog delay, so you hear the same thing said over again and again as it toggles back and forth instead of using a VHF cue channel, they monitor off-air, so it's a big cluster on the weekends and until they remember to reset the HD analog delay and sync it up again. Not a good example. This is a station that could benefit from the full allotted HD power, IMO.
The same group also has a 50KW FM with HD, but it doesn't even have active PAD data or even RDS, yet alone an HD2. Sad.
The engineer for their group is more an I.T. guy and he just gets pissed when I suggest improvements to his group of stations he's responsible for; just doing the minimum to get by and that's it. And don't get me started on how their AM is in shambles with STAs for the past 5 years.
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rbrucecarter5
Guest
ai4i said:
Thanks! I needed a good laugh. I'm aware there has been a trend of late to reverse the migration out of the cities to suburbs, with downtown areas making a comeback. For whatever reason - I don't understand. But the expense of living there and lack of available housing still means that downtown residents are only a fraction of the potential audience, which is spread out in just about every direction from downtown areas. Some, like DFW and LA, have suburbs that are 100 miles across. So if you think of concentric rings of signal strength - the further out you go the larger the area covered. So each time you throw another 10 miles of range at a station, if it is still covering suburbs, you end up with many more listeners, assuming the population density per square mile is constant. The near fringes are VERY important to ratings! To make matters worse, many antenna farms were constructed decades ago, before population growth in suburbs. They definitely got it wrong in both Houston and Dallas, so the newer, more affluent suburbs are 70 to 80 miles from the towers in some cases. So the only thing stations can do is throw up higher towers, more ERP. That sometimes tends to cover a lot of cows in one direction, just to get to the listeners in another direction. When you get that far out, second and even first adjacent rim shots make inroads into the audience, sometimes even showing up in ratings.
HD radio must address these realities to survive. It if can't do a decent job of coverage, which it doesn't at present, then consumers who are aware of it think it unreliable, and rightly so. Power increases are perhaps one way of producing marginal improvements, but when the system already goes 70 miles - I can't help but think that the situation is similar to FM stereo in the 60's, when stereo range was an issue. Receiver improvements made a huge difference in the coverage of FM stereo, and I refuse to believe innovation in the consumer electronics industry stopped after the classic gear of the 70's. Only the innovations are now likely to be done in China, not the US. But a combination of algorithm changes and receiver improvements should be able to increase HD range without trying to saturate the noise floor of the FM band the way the AM band has been destroyed.
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rbrucecarter5
Guest
Our local KUHF 88.7 recently started broadcasting stereo on HD-3. I find the audio quality of both HD-2 and HD-3 really compromised - definitely still better than satellite quality, but curiously fatiguing to listen to. Thankfully HD-2 classical is covered on a different frequency in analog, which is definitely superior now to the HD-2 version.
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rbrucecarter5
Guest
ai4i said:
Yep - guilty of being a classical fan! Along with a lot of other things. About all I can't stomach is country, hip-hop, and Christian praise and worship.
Not a lot of multipath here in Texas, the terrain is pretty flat. I live within sight of the towers 20 miles away, and I am 30 miles from downtown, work 20 miles from downtown so large buildings are around, but spaced out enough I never have issues. 91.7 KUHA is at the limit of the 60dBu contour, but I've never had an issue.
Actually, I think more power is the problem with a lot of these stations. You get 100kW close by tall buildings, it invites reflections. You would be better off with 100W or so if it is line of sight. I know KTXT in Lubbock used to be 10W off of a 600 foot tower - it nicely covered the entire city and the sound was amazing. Lubbock is absolutely flat, so I know KTXT did really well even out of town. Of course out of line of sight, it was gone - but 600 feet goes about 35 miles using a short tower estimation.
One trick I learned - living for a while in Lubbock - I had more luck getting Dallas FM by aiming at a high rise nearby than pointing directly at Dallas, so reflections happen even on weak signals.
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