Any Commercial Success with AM HD ?

[kevtronics]

As I understand it, You Tube digital audio data rate is reduced aka "compressed" from "CD" or original digital recording data rate.

They now use the Audio Opus codec, which is far more efficient than MP3, AAC, or HD Radio's proprietary codec. The audio in that video is accurate to the original recording I made from the tuners. (And note that the Sansui multi-system tuner I used does not do C-Quam's cosine correction; they were a proponent of the Harris system, which did not require it.)

I recall years ago for a while You Tube was applying aggressive audio processing to uploads or streaming play out. That stopped, or became more subtle. Right now You Tube may be using more subtle audio processing, or "normalizing" to set incoming upload maximum digital audio peak level to a set value for streaming play out.

YouTube now has a "Stable Volume" AGC, but it's an option you can turn on or off by clicking on the gear icon. If you don't see the option for it, then it's not in effect for the video you're watching.

 

[yeoldeschool]

And for anyone who might be wondering, to pull off that "Stable Volume" feature, Youtube's servers simply offer alternate, processed encodings alongside the normal (unprocessed) encodings each video comes with. Those processed alternates can be identified by their "-drc" suffixes when using tools like yt-dlp to enumerate a video's available formats (example: https://pastebin.com/raw/4Dn5phvN).

I do not know if Youtube does normalization with simple peak protection limiting to the non-DRC versions of its tracks, but I would not be surprised if it did. Perhaps someone with an account (Kevin?) could upload an unlisted test video so we could find out? Turning down the volume on a copyright-clear song by 30 dB, and then amplifying a single snare hit right in the middle of it to -1 dB, would make for a pretty good test.

Regarding Youtube's modern lossy compression practices, kevtronics is correct there too, though it is worth adding that 128 kbit/s m4a-encapsulated AAC-LC encodings still exist with every video for the benefit of legacy browsers and older embedded players lacking built-in Opus decoding. So if anyone is using an old browser or an aging smart TV, you may end up hearing that format instead of the main Opus audio. (There are also ~48 kbit/s Opus and ~48 kbit/s HE-AAC encodings offered with every video for viewers with extremely slow connections. And for absolutely ancient players, Youtube still offers format 18, which is their last remaining muxed format. It combines 360p video with either 96 kbit/s 22 kHz HE-AAC or 128 kbit/s 44 kHz AAC-LC depending on some internally-determined metric I'm unsure of -- probably a speech/music detection algorithm.)

I also agree about Opus being superior to AAC-LC. But one possible catch comes to mind. When uploading audio to Youtube that is sourced from another lossy encoder, one suddenly faces the phenomenon of cascaded codes fighting each other. Just as they say to never re-encode MP3s as AACs or vice versa, I have to wonder whether the HD Radio codec would fare better through Youtube's AAC encoder, since I believe HD Radio's codec was based somehow on HE-AAC. I ripped the Opus and AAC-LC tracks from kevtronics' video using yt-dlp and uploaded them here, assuming he or anyone else would like to do some comparative Sennheiser-grade listening:

https://files.catbox.moe/uvyo9s.opus (source stats: 1.92MiB audio only opus 138k 48k)
https://files.catbox.moe/o1qeje.aac (source stats: 1.80MiB audio only mp4a 130k 44k)

 

[yeoldeschool]

In this studio tour video of WION 1430, Ionia Michigan, the station owner Jim Carlilele mentions that their internet stream is sourced from an AM Stereo tuner, a Denon TU 680. This lets the general public hear what good AM Stereo can sound like without having to be in the local signal area or buying a hard to come by receiver.

The direct stream URL is http://streaming.live365.com/a83993 and it appears they have it cranked up to 192 kbit/s these days. Nice!

When I started feeding KTNQ in LA to the web as part of our original home-brew website, we simply sent audio from a DA to our ISP. That was back in early 1996. That was really in what you call "early days of internet radio".

I was probably one of the people listening to it, after switching to Sky Dayton's newfangled PPP dial-up numbers that year.

 

[Bongwater]

In the early days of Internet radio, some radio stations, particularly smaller operations, literally took their Internet feeds from a portable radio. Thankfully, that has ended.

Sometimes from a portable radio in what sounds like the outermost fringe area of one's signal in some areas. I heard some really noisy ones

 

[yeoldeschool]

Sometimes from a portable radio in what sounds like the outermost fringe area of one's signal in some areas. I heard some really noisy ones

An AM station in Paso Robles used to do that about a decade ago. There was a tuner located in some local ISP's offices. No audible computer RFI in the signal or anything, but you could hear the RX noise floor during quiet moments.

 

[cc333]

Sometimes from a portable radio in what sounds like the outermost fringe area of one's signal in some areas. I heard some really noisy ones

I'm doing that now!

My private stream is fed via a modded Realistic (Radio Shack) TM-152 AM-Stereo tuner (I'm not currently broadcasting my Part 15 in stereo, but I'm prepared for when I do!). It's not the best (certainly nowhere near a Denon TU 680), but it gets the job done.

I also have a high bitrate (224k, I think), and I try to keep it relatively free of noise, so it sounds fairly decent for what it is.

c

 

[Miss Tuned]

Sometimes from a portable radio in what sounds like the outermost fringe area of one's signal in some areas. I heard some really noisy ones

A station I worked at used to do that - the cheapest portable FM radio in the racks room at the studio, where the signal was already not the best, plugged straight from the headphone output into the mic input on a tired old Dell tower PC.

Even when the signal was behaving itself, you could hear that it was coming from a cheap receiver into a cheap computer because it sounded overdriven and distorted. Most of the time, there'd be a hiss on the signal, or interference from some of the other equipment in the racks room.

After a while, I got rid and took the monitor feed from the STL transmitter (which was also in the rack) which was squeaky clean and processed for broadcast, into a little USB mixer, into a Raspberry Pi and out to stream.

 

[IKHNetworks]

A station I worked at used to do that - the cheapest portable FM radio in the racks room at the studio, where the signal was already not the best, plugged straight from the headphone output into the mic input on a tired old Dell tower PC.

Even when the signal was behaving itself, you could hear that it was coming from a cheap receiver into a cheap computer because it sounded overdriven and distorted. Most of the time, there'd be a hiss on the signal, or interference from some of the other equipment in the racks room.

After a while, I got rid and took the monitor feed from the STL transmitter (which was also in the rack) which was squeaky clean and processed for broadcast, into a little USB mixer, into a Raspberry Pi and out to stream.

Cool that's exactly what I did myself. For those interested in doing the same I found this tutorial on YouTube and this is how I personally setup our encoder.

 

[Kent]

A station I worked at used to do that - the cheapest portable FM radio in the racks room at the studio, where the signal was already not the best, plugged straight from the headphone output into the mic input on a tired old Dell tower PC.

I worked at a couple stations that streamed by plugging a couple transistor radios into the encoders. The oldies station was almost always a straight satellite feed other than liners, forecasts, sporting events, and local sports. When we were live on that station, we got out current temperature by flipping the input switch on the other station's radio and waiting for the jock to announce it. People listening to the stream of that station, of course, heard nothing until we let go of the switch.

It wouldn't seem to be normal there, but I was listening to WOMP-FM at work a few weeks ago, and, for about an hour, I heard static, drops, and pops before the regular quality stream returned. I assume the station was undergoing some type of maintenance and switched to an off-air feed as a backup. It wasn't very pleasant to listen to, and I would've stopped if I weren't a radio person trying to figure out what was happening.

 

[umfan]

WFDF, AM910 Detroit still uses it, I believe.

 

[Martianwxp]

I never saw that. Generally, the feed was from a "split" of the console output, either with a real distribution amplifier or just a parallel feed.

When I started feeding KTNQ in LA to the web as part of our original home-brew website, we simply sent audio from a DA to our ISP. That was back in early 1996. That was really in what you call "early days of internet radio".

I believe several CQUAM AM Stereo station including WION does use the over the air reception for their online stream just to present how the AM Stereo can be. Especially the Stereo separation.

 

[IKHNetworks]

I believe several CQUAM AM Stereo station including WION does use the over the air reception for their online stream just to present how the AM Stereo can be. Especially the Stereo separation.

Yes it's true WION does indeed use an AM stereo tuner to showcase how good AM Stereo sounds. Another one that does this is WRDN 1430 Reel Country also does the same thing.

 

[yeoldeschool]

Yes it's true WION does indeed use an AM stereo tuner to showcase how good AM Stereo sounds. Another one that does this is WRDN 1430 Reel Country also does the same thing.

Is there a special streaming URL for hearing that? I found http://streaming.live365.com/a76502 but its audio isn't coming from an AM receiver (it extends all the way to 16 kHz).

 

[Reverend]

Does anyone know if Radio Martí on 1180 are running AM HD? I ask because I was trying to ID a station on 1170 kHz (which turned out to be WAVS) and there was a very high level of on-channel noise. The noise didn't sound 100% random, as if it had structure, making me think it might be HD on Martí. Without having an AM HD receiver, I wasn't able to check.

 

[Mediafrog+]

Does anyone know if Radio Martí on 1180 are running AM HD? I ask because I was trying to ID a station on 1170 kHz (which turned out to be WAVS) and there was a very high level of on-channel noise. The noise didn't sound 100% random, as if it had structure, making me think it might be HD on Martí. Without having an AM HD receiver, I wasn't able to check.

I have never seen any reports of Radio Marti using HD. And why would they?

KOTV 1170 in Tulsa uses HD, and my receiver here in Houston senses the HD signal but doesn’t lock due to a local station on 1180.

I have seen reports of KSL 1160 in Salt Lake City using HD, but cannot confirm if that is actually active.

 

[cc333]

I have never seen any reports of Radio Marti using HD. And why would they?

KOTV 1170 in Tulsa uses HD, and my receiver here in Houston senses the HD signal but doesn’t lock due to a local station on 1180.

I have seen reports of KSL 1160 in Salt Lake City using HD, but cannot confirm if that is actually active.

KSL 1160 does indeed use HD, and it was active as recently as last month (when I was listening in my car one evening, the radio locked on to KSL's HD signal for a few seconds).

c

 

[IKHNetworks]

KSL 1160 does indeed use HD, and it was active as recently as last month (when I was listening in my car one evening, the radio locked on to KSL's HD signal for a few seconds).

c

Does AM HD sound just as good as AM stereo? My HD Radio SageEAN HD18 picks up WMLV (AM Stereo) but I have never heard AM HD

 

[cc333]

Does AM HD sound just as good as AM stereo? My HD Radio SageEAN HD18 picks up WMLV (AM Stereo) but I have never heard AM HD

It's hard to say, but, while it was quieter, in my opinion, the overall sound quality of AM stereo (or, frankly, even normal mono AM on a decent radio) is better, if only because there's no artifacts from the HD encoder's relatively low bitrate. But, I'm picky about such things; the average person probably wouldn't care.

c

 

[kevtronics]

Does AM HD sound just as good as AM stereo?

 

[HTX]

KOTV 1170 in Tulsa uses HD, and my receiver here in Houston senses the HD signal but doesn’t lock due to a local station on 1180.

Every so often up here in Montgomery County I’ve been able to lock in KOTV but never for very long. I’m far enough away from that reduced 1180.