I notice today that 92.3 WXRK's HD1 audio is a second behind the analog audio. Being that I am in an area where it constantly switches between analog and HD and I can't force analog, it's quite annoying. Therefore, I am not going to listen to it, even though I am within the city grade coverage area. The HD reception is only reliable enough to find out what song is playing.
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HD Radio Synchronization
- Thread starter nd2023
- Start date
Yep. HD Radio: klutzy, kludged, and not getting any better. The analog-digital time-synch just one of a towering stack of persistent problems. HD's a maintenance hog at a time when radio engineering can barely keep up with current multi-station cluster basic demands, it costs a ton when the industry is struggling with dropping revenues and mounting other costs, it aggravates audience fragmentation (at least potentially) when existing audiences are already being picked apart by competing other entertainment sources....
Oh, yes, and lest we forget. The coverage sucks.* And unless the analog is just running an HD-1, the vaunted "digital improvement" actually sounds worse than the original analog.
Gee, wonder why nobody's wiggling out to buy HD Radios. If they can find one in a store.
*Footnote for HD's six friends: Yeah. I know. The FCC just authorized the digital power increase....whoopdee doo. As I predicted, there hasn't been a single persuasive case of claims that a station's hike to -14 or -10 has dramatically improved coverage or produced measureable digital audience increase.
Oh, yes, and lest we forget. The coverage sucks.* And unless the analog is just running an HD-1, the vaunted "digital improvement" actually sounds worse than the original analog.
Gee, wonder why nobody's wiggling out to buy HD Radios. If they can find one in a store.
*Footnote for HD's six friends: Yeah. I know. The FCC just authorized the digital power increase....whoopdee doo. As I predicted, there hasn't been a single persuasive case of claims that a station's hike to -14 or -10 has dramatically improved coverage or produced measureable digital audience increase.
Nick said:
I've been thinking about the whole sync thing and came to my own plan which probably won't work as if it did they'd be using it.
The analog audio comes from delaying the board audio to match the HD audio. Can they take the analog audio from an HD monitor? That is to say the signal that feeds the analog transmission comes from an HD monitor. I've worked in radio and believe the time from microphone to radio is small enough where it won't be a problem.
Again, if this had no problem I'm sure they'd be using this. So, flame free, please tell me how this would not work at all. Thank you in advance for the education.
You sync the audio with an Eventide delay unit at the Tx site. It's not hard.
Yes, we understand how it's done. And of course it's not difficult to sync two audio streams using a profanity delay, although it's really dopey and low-tech to do it that way.
The trick is keeping the two separate streams in sync. One or both of them drift so the sync is soon lost. That's the whole issue.
It's lousy engineering. You know: the hallmark of HD.
Reminds me of how Packard Motor Company scrambled like the dickens back in the early 1950s to come out with a "hardtop" (door-pillarless) 2-door to compete with leading models from GM and Ford. Unfortunately they didn't have time to properly engineer the body with the result: the cars leaked like they had screens instead of glass windows.
Packard's solution: they put waterproof upholstery in the cars.
The trick is keeping the two separate streams in sync. One or both of them drift so the sync is soon lost. That's the whole issue.
It's lousy engineering. You know: the hallmark of HD.
Reminds me of how Packard Motor Company scrambled like the dickens back in the early 1950s to come out with a "hardtop" (door-pillarless) 2-door to compete with leading models from GM and Ford. Unfortunately they didn't have time to properly engineer the body with the result: the cars leaked like they had screens instead of glass windows.
Packard's solution: they put waterproof upholstery in the cars.
This may be a matter of opinon, but I don't think using a $4K unit should be considered low-tech or "dopey". Eventides are responsible for keeping hundreds of stations safe at the studio level, and being that all program audio flows through them, they're built to kick ass.
Speaking of degradation, this new thing where OTA TV stations are carrying subchannels is asanine. Similar to the HD argument, these subs (which are bitrate-starved to begin with) take away what little bandwidth remains from the main channel. The result, especially in HD stations, is a picture that pixelates during color changes, and hideous looking subchannels. As a mode of comparison, DTV transmitters can only pass 19.393 Mbps of data...divide that available bandwidth among 3 or 4 channels, and you're left with an HD channel that passes maybe 10 Mbps. Non-broadcast stations that send their feed directly up to the bird are typically sending ONE channel out on 25-30 Mbps. No wonder Discovery HD looks so sharp.
And in similar fashion, the subs on TV are junk channels where there is either no available inventory, or the clients get bonus spots for free.
Sorry to break away from radio, but I just wanted to get that off my chest.
Speaking of degradation, this new thing where OTA TV stations are carrying subchannels is asanine. Similar to the HD argument, these subs (which are bitrate-starved to begin with) take away what little bandwidth remains from the main channel. The result, especially in HD stations, is a picture that pixelates during color changes, and hideous looking subchannels. As a mode of comparison, DTV transmitters can only pass 19.393 Mbps of data...divide that available bandwidth among 3 or 4 channels, and you're left with an HD channel that passes maybe 10 Mbps. Non-broadcast stations that send their feed directly up to the bird are typically sending ONE channel out on 25-30 Mbps. No wonder Discovery HD looks so sharp.
And in similar fashion, the subs on TV are junk channels where there is either no available inventory, or the clients get bonus spots for free.
Sorry to break away from radio, but I just wanted to get that off my chest.
You get no argument from me, Adam, about the quality of Eventide stuff. It's been great ever since the very first giant rack-mount 1972-vintage "Instant Phaser." It's just IMO a waste of a $4K box to use it (contrary to its design) to even up two discrete audio paths with time discrepancies. Profanity delays should be used to protect stations from on-air profanity and libel, not as a Band-Aid (tm) to fix design shortcomings in a hybrid digital transmitting scheme.
The HD encoding delay introduces a whole host of real-world programming problems, all of which have been exhaustively discussed and debated here and elsewhere. And judging from over seven years of experience with HD Radio, it appears most broadcasters agree: the attendant problems aren't worth the ephemeral-at-best "promise" of digital on-band radio.
The HD encoding delay introduces a whole host of real-world programming problems, all of which have been exhaustively discussed and debated here and elsewhere. And judging from over seven years of experience with HD Radio, it appears most broadcasters agree: the attendant problems aren't worth the ephemeral-at-best "promise" of digital on-band radio.
So if a station uses the profanity delay, what if they need to...you know...actually delay possible profanity from a live broadcast? The profanity could be dumped on the analog, but you'll be able to hear the curse words in full HD quality, and the synchronization will be messed up.
Nick said:
I'd bet plenty of profanity has been uttered in transmitter rooms by the engineers who have to keep fixing faulty HD equipment. As you noted on the New York board, Z100's digital transmitter is down again:
http://boards.radio-info.com/smf/index.php?topic=165283.0
Nick said:
It's a separate unit that is placed at the Tx site, silly. No jock puts his/her hands on it.
WeekendsAdam said:
No no, it was a good post.
I guess content always wins out over engineering on these things. The idea around the digital televisions subchannel scheme was probably for one HD channel -OR- multiple SD channels but that's been stretched to the limit. Many ABC O&O's are running two 720p HD channels (ABC HD and some Lifestyle and Living channel or somesuch.) The results are predictably nauseating.
Of course, some stations are abusing the multichannel SD scheme by putting 6 or more subchannels into the stream. LA's KVMD has a whopping nine subchannels of ethnic programming!
And to bring it back to radio, adding an HD-4 or 5 or whatever is not going to add anymore value to the digital scheme, it will only degrade the quality of the other subchannels.
Now this may seem like a stupid question, but doesn't the HD equipment automatically include some bulletproof synch hardware to always keep the analog and digital in line? It seems like that would be part of the hardware of the HD setup. ???
Not a stupid question at all, Zach. But the answer is: no.
There is no hardware or software to sync the analog and digital streams. Stations use an outboard profanity delay purposed strictly for delaying the analog to match the encode-delayed digital. It's about 8 seconds.
Talk about kludgey and Rube Goldberg.... :
There is no hardware or software to sync the analog and digital streams. Stations use an outboard profanity delay purposed strictly for delaying the analog to match the encode-delayed digital. It's about 8 seconds.
Talk about kludgey and Rube Goldberg.... :
Zach said:
Why are additional sub-channels an 'abuse' when ATSC specifications allow for it? You may not like the programming or even the quality of the stream (although much of the quality problems stem from the original source).
But for a city as diverse as Los Angeles, there are many minority communities that appreciate watching programming in their own language--that appreciates all nine channels of it that KXLA provides.
c5
Carmine5 said:
If the ATSC standard allows for unlimited SD subchannels then that's my mistake. I thought they suggested no more than four. Anything more than four in my experience leads to really poor video quality. But I didn't have pristine feeds to compare them to.
But then I don't have a pristine feed of some of the HD-2 / HD-3 content to compare it to, to know some of those channels sound like crap.
The "pristine feed" to compare it to could be an MP3 file of the song that's playing. Some HD2s sound worse than a 64k MP3. Heck, some HD stations sound worse than the web stream of the station.Zach said:Carmine5 said:
If the ATSC standard allows for unlimited SD subchannels then that's my mistake. I thought they suggested no more than four. Anything more than four in my experience leads to really poor video quality. But I didn't have pristine feeds to compare them to.
But then I don't have a pristine feed of some of the HD-2 / HD-3 content to compare it to, to know some of those channels sound like crap.
Zach said:
In Northern Virginia, WNVC (displayed channel 30) has an apparent 10 SD channels, but it's a trick -- they use both channels 24 and 30 to do it. http://en.wikipedia.org/wiki/MHz_Networks
- Jonathan
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