Audio pops on Fox Chicago DT - AVS Forum
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post #1 of 60 Old 02-27-2002, 04:23 PM - Thread Starter
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...Seems to only occur on the network feeds..I hear it on analog and digital audio decoding on my receiver, tho its worse on digital. Anyone else hearing cracks/pops on FOX32 DT?

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post #2 of 60 Old 02-27-2002, 04:32 PM
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None here.

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post #3 of 60 Old 02-27-2002, 04:59 PM
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Yep, I have been hearing the pops also on 32-1. I am currently using a Panasonic TU-HDS20 to receive the signal, but I am getting a Zenith DTV1080 next week. It should be interesting to see if I still get the popping with the new receiver.

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post #4 of 60 Old 02-27-2002, 07:01 PM
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Have you also noticed that they are NOT transmitting a Dolby Digital signal but just a PCM????
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post #5 of 60 Old 02-27-2002, 07:38 PM
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I doubt a new reciever will effect anything.. I've got the popping sound too. Very annoying. But I got to believe it's just another part of the fox "No HDTV" Conspiracy

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post #6 of 60 Old 02-28-2002, 12:04 PM
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I really do not think it is anyones Set Top Box. I mean, I only hear the "Pops" on FOX, not on any other channels. If it was your Boxes you would most likely hear it on other channels as well. Also, it only happens during their network shows. Not on Local news, etc. So it has to be bad audio that they are playing. What I want to know is how can we tell them about it to get it fixed??? It is obviosly just a Chicago problem, because I have not seen posts about it happening in other cities.

Thanks Tom
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post #7 of 60 Old 02-28-2002, 02:36 PM
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I am getting them too.
I sent FOX an email, but only got a canned response.
It only affects the Network Feeds.
Perhaps someone can call their control room and let them know
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post #8 of 60 Old 02-28-2002, 05:50 PM
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Hey Rad, they can't be broadcasting PCM audio.
Your decoder may be misinterpreting it as PCM, or more likely your STB is internally decoding the Dolby Digital data stream and sending PCM out of the digital jack.
You might want to check to see if there is some hidden menu on your STB that will select between PCM and DD on the output.
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post #9 of 60 Old 02-28-2002, 06:28 PM
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Quote:
Originally posted by mbabbitt
Hey Rad, they can't be broadcasting PCM audio.
Your decoder may be misinterpreting it as PCM, or more likely your STB is internally decoding the Dolby Digital data stream and sending PCM out of the digital jack.
You might want to check to see if there is some hidden menu on your STB that will select between PCM and DD on the output.
My STB works fine for all other channels that have DD audio, only WFLD-DT shows PCM. It used to show DD2.0 before WFLD-DT had some hardware problems on their end and it's been PCM ever since.
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post #10 of 60 Old 03-01-2002, 11:11 AM
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I called Wednesday PM and asked for engineering. I was able to speak with someone named Randy and explained the problem. He didn't have any explanation but said there had been no changes to their setup since they changed transmitters prior to the Superbowl. I haven't been able to watch in primetime since then to see if anything has improved.
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post #11 of 60 Old 03-04-2002, 03:15 PM
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Hi Rad.

If your STB works fine with all other channels, then perhaps the station is corrupting the preamble/header in the data stream and you're STB is reading this as PCM. In this case, there's nothing that you can do and while WFLD is conveying a Dolby Digital data stream, it's not correct.

I imagine that this only happens on stereo programming and not multichannel? If this is true, then most likely the folks at WFLD are using a licensed software encoder within their ATSC broadcast encoder, and this audio encoder isn't doing the job properly.

I'll give them a call at WFLD and see if I can't help them straighten it out. It may mean going back to the ATSC encoder manufacturer, so don't hold your breath.
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post #12 of 60 Old 03-04-2002, 05:32 PM
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To All,

M. Babbitt called me to tell me about this thread and the problems you've reported.

We monitor off-air in Master Control on a Sony KW-34HD1 and do not hear it.

Using a Harris Demod (guts made by Samsung) and feeding the digital output of the Harris into a Dolby DP562 decoder, we intermittently get audio pops at the studio site. Using the same setup at the transmitter site, (with a probe into the transmission line that feeds the transmitting antenna) to get an RF feed for the Demod, the audio is 99.999% clean.

We are still trying to get to the bottom of this elusive problem, but our engineering focus is to keeping our NTSC analog transmitting plant operating correctly, since this is what determines our audience ratings.

We plan on making some changes in processing equipment in the next few weeks (barring any further emergencies at the analog transmitter) to see if we can identify the source of the problem.

The person named Randy one of you contacted was not an "Engineer", but our operations manager. He has recently left for greener pastures. But he was basically correct in stating we have not made any changes in our processing path in the last six months.

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post #13 of 60 Old 03-04-2002, 06:34 PM
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Thanks for the update Bob. I was happy just to get humans when calling a station, the competition usually just has the standard AVR nightmares. 'Cops' on Saturday night was clean (no popping), and that's the show that's had the most noticeable problems before.
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post #14 of 60 Old 03-05-2002, 06:39 AM
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Quote:
Originally posted by mbabbitt
[b]Hey Rad, they can't be broadcasting PCM audio.
B]
Hey Mike-
PCM can be done with certain encoders, such as the Divicom's,
(and the Lucent with the audio option board). We have done that
here. Works fine on most STB's as long as you don't need to maintain lip sync, as the pcr slips when using pcm audio.
yes, it is not the atsc standard, but is a "cheap" and easy way
to add secondary audio, with constraints in mind!

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post #15 of 60 Old 03-05-2002, 07:19 AM
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Hey Bob,

Transmitting a non-compliant stream on your DTV channel doesn't do anyone any good, and might expose your station to FCC action. There are rules for DTV operation. Please follow them. There are enough headaches with compatibility as it is. You don't need to add to it with home-brew solutions.
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post #16 of 60 Old 03-05-2002, 09:52 AM
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Quote:
Originally posted by hphase
Hey Bob,

Transmitting a non-compliant stream on your DTV channel doesn't do anyone any good, and might expose your station to FCC action. There are rules for DTV operation. Please follow them. There are enough headaches with compatibility as it is. You don't need to add to it with home-brew solutions.

H phase, I'm sure you mean well, but maybe you should have the
full picture before you judge. We do a lot of beta testing here.So,
You worry about your domain, while we'll proceed as we are
in cooperation with specific encoder and stb manufacturers to
determine applicable solutions for some of these compatibility issues.

Bob

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post #17 of 60 Old 03-05-2002, 10:08 AM
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Hi Bob Davis.

Thanks for catching my mistake. You're right, and I should have said that "...they shouldn't be broadcasting PCM," rather than "can't." It's interesting to hear what's going on in the trenches as equipment and all the standards get tested in real world situations.

Our pals at Fox in Charlotte are pretty sharp and on the ball with this stuff, so I'll defer to your real-world experience rather than my book and standards learning.

BTW, the Super Bowl worked out pretty well, didn't it? We had a very successful broadcast here in SF at our local station, KTVU. It's nice to see it all works as we designed it!

Regards.
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post #18 of 60 Old 03-05-2002, 10:17 AM
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Dolby digital is also the standard for DVD, however I was surprised to find that when I tried to play the Wingspan DVD I had to switch to PCM audio.
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post #19 of 60 Old 03-05-2002, 10:25 AM
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Hey Mike-Good to see you here..

Superbowl went very well for us. We Did discover, as I'm sure Rocky G. has passed on, that there are some consumer decoder issues with switching between DD2.0 and DD5.1 on the fly, but otherwise it worked. Did find a bug with the extended data stream and "certain" decoders as well, but I think that is being handled .

As to PCM, found out these things while doing SAP testing. Just tried the PCM and found it works, due to most stb's being satellite
based, tho it's not ATSC compliant.

Seems the best way to do SAP is to add an additional DD stream, then map the additional audio pid with the primary video under psip as a virtual channel. Works very well, and the consumer
actually knows that they're on the SAP channel by the banner.

Bob

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post #20 of 60 Old 03-05-2002, 11:51 AM
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Quote:
Originally posted by bdfox18doe



H phase, I'm sure you mean well, but maybe you should have the
full picture before you judge. We do a lot of beta testing here.So,
You worry about your domain, while we'll proceed as we are
in cooperation with specific encoder and stb manufacturers to
determine applicable solutions for some of these compatibility issues.
Bob,

You're right, I DO mean well. Most, if not all of the MPEG encoders offer a choice for "PCM" audio, and lots of people use it for distribution. It is NOT to be used for over-the-air transmission, where Dolby Digital is the standard. Rest assured that I AM in my domain. Non-compliant over-the-air solutions will not go over well in either Washington or the marketplace.
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post #21 of 60 Old 03-05-2002, 12:43 PM
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Spwace:

I'm not familiar with that particular DVD, and we're going off topic here, so I'll keep this short.

There may have been some trouble with the authoring of the data stream on that DVD which prevented your decoder from dealing with it properly. Also, there may be some issue with your decoder being able to deal properly with SurroundEX flags, if this particular DVD was released in SurroundEX.

99% of the time, selecting PCM on your DVD player will engage the internal two-channel Dolby Digital decoder that is present in all DVD players. Ignoring dts for the moment, unless the DVD has been released with a separately mastered PCM track burned into it (very rare due to the space constraints and the desire for all the video extras that are put on most DVDs), the Dolby Digital track is the source for all audio out of the DVD player. In fact, a Dolby Digital track is present even on dts DVD releases and because of the scalability of Dolby Digital, is still used as the source for any stereo audio output.

I'd guess that if the "Wingspan" DVD is a SurroundEX release, the reason it isn't playing through your decoder is that your decoder isn't reading the SurroundEX flag properly and muting. Also, it's possible that "Wingspan" wasn't released in Dolby Digital since the standard requires either a PCM OR a Dolby Digital track, although it's rare that a DVD is released today with only a PCM track.

This didn't turn out as short of an answer as I had hoped. Sorry about that.
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post #22 of 60 Old 03-05-2002, 11:51 PM
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The audio accompanying the opening menu of the DVD is DD2.0, however the main program is PCM. Neither my Sony DVP-S530D DVD player or Nak CA-1 preamp indicate any presence of AC3 encoded audio channels. The displayed audio bit rate is 1536 Kbps.
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post #23 of 60 Old 03-06-2002, 03:08 AM
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Samsung SIR-T150, popping is really bad on Fox, needs to be addressed. Happens either thru our receiver or direct L/R input to the TV.

Tom
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post #24 of 60 Old 03-07-2002, 01:18 PM
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I watched Fox News Sunday, and the feed was clean.
I tried to watch Titus last night, but the pops are back.
(Not quite as bad as before, but enough to make me
switch back to analog Ch 32)

I checked again during the news at 9:00, and
the audio was clean.

I hope FOX 32 can get this resolved.
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post #25 of 60 Old 03-07-2002, 10:29 PM
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I have heard that some STB's have trouble locking to the audio if the bit rate is lower than 384 Kbps. Don't know if this is the same problem, but you might want to check the bit rate just for drill.
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post #26 of 60 Old 03-11-2002, 10:41 AM
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Fox Chicago Audio bit rate is 384kbit/s, Coding Mode 2/0 (L,R), Coding Standard is Dolby AC-3, Sampling Rate is 48khz, Language is English, Bitstream mode is Complete Main, Dolby Surround Mode is set to Dolby Surround (choices are Not Indicated, Not Dolby Surround, Dolby Surround), Audio Prod Info is set to No, Copyright is set to ON, Original is set to ON, Dynamic Range is set to Film Standard (choices are Film Standard, Film Light, Music Standard, Music Light, Speech, None/Custom), RF Protection is set to OFF, Deemphasis is set to ON, DC Filter is set to ON, Low Pass Filter is set to ON, Embedded Src12 is indicating n/a, same for Embedded Src34. The audio PID is 36.
We have asked Tandberg/NDS, the manufacturer of our ATSC Encoder, to review the hardware and software revision levels of the encoder to see if there might be a hardware or software update that was issued to address the audio pop problem. Also, arrangements are being made to borrow an external Dolby AC3 encoder to do the audio AC3 encoding external to the Tandberg encoder to see if this points us toward the problem.

Bob Olsen
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post #27 of 60 Old 03-11-2002, 05:15 PM
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To all,

I changed the encoder setup at WFLD-DT FOX Chicago about 4:30PM today (3/11). I would appreciate feedback on whether this affected the audio pops ( I don't expect it to, but ...) and any other reception changes you may observe.

Bob Olsen
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post #28 of 60 Old 03-11-2002, 06:46 PM
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No audio pops tonight or last night, however about a week ago it was awful.

R. B.
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post #29 of 60 Old 03-11-2002, 07:14 PM
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I agree--the audio popping appears to be gone, but it disappeared at least a few days ago.

--Eric
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post #30 of 60 Old 03-12-2002, 08:28 AM
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NOTHING was changed in the system until 3/11 in the afternoon. I can not explain what would make the audio pops just come and go randomly like this. Please keep me posted.

Bob Olsen
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