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#1
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Radio processing
Yesterday flooding in the Chicago area knocked out power to the Willis Tower (née Sears Tower) atop which the broadcast antenna for WFMT 98.7 FM sits, a station I have been in the habit of listening to. There was static the whole day. This morning it was back on the air with the help of WBEZ, broadcasting from the top of the John Hancock building. The only difference is that now WFMT sounds nasty and tizzy, almost like it's clipping. I assume everything is being run through WBEZ's processing chain. As best I can tell through a few minutes of listening, the WFMT internet stream is unaffected by the sound changes in the analog broadcast. WFMT is a classical station and WBEZ is a public radio news and talk station (used to have some jazz, but not anymore). I'm surprised there would be such a dramatic difference between stations. What kinds of things are some of these stations likely doing to the audio and why? |
#2
Posted to rec.audio.pro
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Radio processing
On 19/05/2020 17:59, Tatonik wrote:
As best I can tell through a few minutes of listening, the WFMT internet stream is unaffected by the sound changes in the analog broadcast. WFMT is a classical station and WBEZ is a public radio news and talk station (used to have some jazz, but not anymore). I'm surprised there would be such a dramatic difference between stations. What kinds of things are some of these stations likely doing to the audio and why? There is normally an audio "optimiser" in the feed to the transmitter, doing things like tailoring the frequency profile of the transmitted material so all the music comes out sounding similar, and compressing the signal to make it more pleasant to listen to in fringe areas, with fewer surprises as levels change between tracks or other audio segments. Basically a multiband compressor. There is an independent feed to the streaming server, which tends to be closer to what is in the source feed. This is one very popular make of optimiser. https://www.orban.com/radio-audio-processors -- Tciao for Now! John. |
#3
Posted to rec.audio.pro
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Radio processing
Tatonik wrote:
Yesterday flooding in the Chicago area knocked out power to the Willis Tower (née Sears Tower) atop which the broadcast antenna for WFMT 98.7 FM sits, a station I have been in the habit of listening to. There was static the whole day. This morning it was back on the air with the help of WBEZ, broadcasting from the top of the John Hancock building. The only difference is that now WFMT sounds nasty and tizzy, almost like it's clipping. I assume everything is being run through WBEZ's processing chain. My first guess is that they are getting the audio over to the other site through some lossy-compressed mechanism. If they have internet codecs used for live remotes, that would be the first way I'd do it. Nobody has isdn lines around anymore. The processing chain is the least of your worries. What kinds of things are some of these stations likely doing to the audio and why? They could tell you but they'd have to kill you. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#4
Posted to rec.audio.pro
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Radio processing
Scott Dorsey wrote:
My first guess is that they are getting the audio over to the other site through some lossy-compressed mechanism. If they have internet codecs used for live remotes, that would be the first way I'd do it. Nobody has isdn lines around anymore. The processing chain is the least of your worries. _________ Lossy-data reduction does not cause "nasty and tizzy" effects, as the original poster referred to. Questionable processing chain settings, as JW mentioned, or less than ideal gain-staging, can. |
#6
Posted to rec.audio.pro
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Radio processing
On Wed, 20 May 2020 14:15:19 +0100, John Williamson
wrote: On 20/05/2020 12:03, wrote: Lossy-data reduction does not cause "nasty and tizzy" effects, as the original poster referred to. Questionable processing chain settings, as JW mentioned, or less than ideal gain-staging, can. Lossy data compression and digital transmission can and does cause many artifacts, including "nasty and tizzy" ones as well as burbling mud and other problems when the error correction fails. I hear these all the time as I travel round using a DAB radio. If you must criticise, at least do so correctly. Haven't heard burbling mud for many years. I used to get it often on my Arcam home tuner, but I think that was their first effort, and it had a lousy front end. Anyway, the mud is what you got when you were running out of signal. I guess these days they just drop the audio before error correction is denied signal to that level. All still better than FM though. The slightest multipath, inevitable in urban driving, resulted in swishes and hisses. I used to inch back and forth in traffic jams to find an exact location where the signal was clean. DAB relished multipath - it just meant more signal. d -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#7
Posted to rec.audio.pro
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Radio processing
On 20/05/2020 14:35, Don Pearce wrote:
Haven't heard burbling mud for many years. I used to get it often on my Arcam home tuner, but I think that was their first effort, and it had a lousy front end. Just lately, I have been driving a bus without a radio fitted, so have been driving round using a cheap portable one sitting on the dash, which still does the burbling mud just before it mutes. FM would be better, possibly, as the degradation is easier to live with, but only on the news station I usually listen to. Music or drama are non-starters on either system -- Tciao for Now! John. |
#8
Posted to rec.audio.pro
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Radio processing
John Williamson wrote:
Lossy data compression and digital transmission can and does cause many artifacts, including "nasty and tizzy" ones as well as burbling mud and other problems when the error correction fails. I hear these all the time as I travel round using a DAB radio. If you must criticise, at least do so correctly. ________ By now you should know where I'm coming from in that regard, lol! Formats have evolved to the point where there is usually less degradation or undesirable qualities from the formats themselves than from processing choices in production, post, and in the case of radio(analog or DAB): the transmission chain. |
#9
Posted to rec.audio.pro
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Radio processing
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#10
Posted to rec.audio.pro
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Radio processing
On Tuesday, May 19, 2020 at 11:59:43 AM UTC-5, Tatonik wrote:
... The only difference is that now WFMT sounds nasty and tizzy, almost like it's clipping. That sounds like a really weak FM signal which may well be since they are probably using WBEZ's emergency backup transmitter which could be much lower power. |
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