some viewers Can't hear our audio

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PID_Stop
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Re: some viewers Can't hear our audio

Post by PID_Stop » Wed Jan 16, 2013 9:31 am

NECRAT wrote:Try changing the compression type from AC-3 Pass-Through to AC-3 Compression or similar.
Mike, on all of our Harris or Tandberg encoders that would have the effect of replacing the external AC-3 feed with the internal AC-3 encoder... but his Tiernan apparently doesn't have an internal AC-3 encoder. So even if that setting would be allowed, I expect it would kill all audio for everyone. If I had to make a wild guess at this point, there's something set wrong in the AC-3 metadata. I'd also be suspicious of what that "AC-3 Preamble" setting in the Tiernan is all about, but still my strongest suspect is the AC-3 encoder itself.

rburleson
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Re: some viewers Can't hear our audio

Post by rburleson » Wed Jan 16, 2013 10:25 am

The only option on the Tiernan Titan Encoder is AC-3 Pass through or PCM. it is passing through the previously encoded AC-3 audio from the Ensemble Designs Avenue 7630 module.

"The 7630 encoder is fed from selected outputs of the main module’s channel mixer and shuffler. The resulting encoded bitstream can be output both on an AES output and embedded into the SDI output."

I have both the embedded SDI and the AES running into the Titan after a suggestion in this thread.
But still no luck.
Today I noticed that even one of our older LCD TVs stopped receiving our audio but the other one still gets it just fine. Weird.

w9wi
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Re: some viewers Can't hear our audio

Post by w9wi » Wed Jan 16, 2013 4:16 pm

Something that concerns me...

That screen shot says the video is being encoded as MPEG-4. While I haven't tried it myself, it's my understanding most consumer receivers will not decode MPEG-4 video.

Point being, are you certain that screen shot actually reflects what's loaded in the encoder? Is it possible there's some kind of "apply" or "send" function that's necessary to send/activate that configuration? I would think you would be getting numerous complaints of missing video with that setup.
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Pleasant View, TN EM66

rburleson
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Re: some viewers Can't hear our audio

Post by rburleson » Wed Jan 16, 2013 4:55 pm

No problems with missing video... just missing audio.

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Re: some viewers Can't hear our audio

Post by w9wi » Wed Jan 16, 2013 6:48 pm

rburleson wrote:No problems with missing video... just missing audio.
Yeah, just reread my reply & saw I didn't bother to type my point :)

Point being, maybe the audio settings that are actually active in the encoder are not those that show up on that screenshot?

Because I would think if the video settings we're seeing were actually in use, you *would* have missing video. Since you aren't having any video problems, I'm thinking maybe you're actually encoding with different settings -- both video and audio.

The other thing I'm wondering... is if there's a missing PSI/PSIP table or bad data in that table?

The 36 PID for the audio is transmitted in two places -- the Program Map Table (PMT, which tells the TV which media PIDs are associated with which program) and the Terrestrial Virtual Channel Table. (TVCT, which tells the TV you want your station to come up as channel 5.1 even though it's broadcasting on channel 25) The values you're using, 33 for video and 36 for audio, are standard for Program #2 -- so I might expect some TVs to be able to guess them even if they aren't being transmitted.

(I haven't seen what happens if there's no PMT, but every TV I've ever tried can decode signals with no TVCT)

What would happen if your PSIP generator was transmitting the wrong audio PID? Might some receivers pull the audio PID from the TVCT -- and not find anything there?

Strictly a guess, but I tend to think that's the kind of thing to look at when it works on some TVs but not on others.
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w4cl
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Re: some viewers Can't hear our audio

Post by w4cl » Thu Jan 17, 2013 10:57 am

NECRAT wrote:Try changing the compression type from AC-3 Pass-Through to AC-3 Compression or similar.
That is what I was going to say. You would nornally use the AC-3 Pass-through for an external Dolby encoder like a DP-569. With it in AC-3 Pass-through, he is still only passing PCM and not AC-3. Turn on AC-3 Compression and it should start lighting up all receivers.

The video needs to be changed from MPEG4 4:2:0 to MPEG2 4:2:0. That may also be part of the issue.

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Re: some viewers Can't hear our audio

Post by grich » Thu Jan 17, 2013 2:14 pm

Shouldn't be using PID 33. PIDs 0 thru 47 are considered invalid now...they were OK to use until a few years ago, and some receiver chipsets may not be able to figure them out.

Your program 1 PMT PID should be 48, video 49, audio 52 (all PIDs I list are in decimal format).

I've attached a chart I think came from Harris back when the allowed PIDs changed...
New_ATSC_PIDS(1).pdf
(25.26 KiB) Downloaded 831 times

rburleson
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Re: some viewers Can't hear our audio

Post by rburleson » Thu Jan 17, 2013 4:42 pm

I am using an AC-3 encoder prior to the encoder since the Titan encoder has no AC-3 encoding at all. The only choices are PCM or AC-3 Pass through.

Regarding the issue we have been having with some Older TV Sets not being able to receive our audio…
Again… Newer TV sets receive our audio just fine BUT older model LCD TV s and SD TV sets with Set top HD Coverter boxes do not.

Steps taken:
Installed AC-3 Encoder and Decoder cards on the 7660 Ensemble Designs audio embedder. RESULT: After that did not fix the problem we concluded that possibly the bit rate was too high on the AC-3 Audio encoder card and that there is going to be a required software update to address this.
Reset the audio out on the AirBox to AC-3 at the lowest bit rate. 244 Kbps? And reset the settings on the 7660 card to accommodate the incoming AC-3 audio: RESULT: No change
Bypassed the Ensemble Designs AVENUE box altogether and took the signal directly from the PlayBox to the Tiernan Titan Encoder. RESULT: No change still had the problem.
Bypassed the PSIP just in case that the audio PIDs may be mismatched or that it may be causing problems. RESULT: No change
Talked to Steve Finton at HARRIS transmitters and he walked me through all the menus and the transmitter looks like it is performing great. He said that he had never heard of anything like this issue in any service calls. He recommended that I try powering down the transmitter for 10 minutes and restart to see if maybe that help. RESULT: No change.
The only other possible links in the chain. The Titan Encoder OR the Ensemble Designs 7110 DA in the transmitter building.
Those are the only other pieces of equipment between the AirBox and the Transmitter.

I am not sure how the Encoder could be the issue if it is AC-3 passthrough but maybe something in the encoding some setting somewhere?
I am Just really grasping at straws.
But it is unlikely that both 7110 cards in the Ensemble designs would both be faulty at the same time.

Guys I am really pulling my hair out over this one. I feel like I am just chasing my tail.
I appreciate the help from each and every one of you.
I am truly hoping somebody can help me find the solution soon.

Thanks again for your help!

I will try those PIDs to see if that may be the issue.
Thanks again

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NECRAT
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Re: some viewers Can't hear our audio

Post by NECRAT » Mon Jan 21, 2013 9:02 pm

rburleson wrote:I am using an AC-3 encoder prior to the encoder since the Titan encoder has no AC-3 encoding at all. The only choices are PCM or AC-3 Pass through.

Guys I am really pulling my hair out over this one. I feel like I am just chasing my tail.
I appreciate the help from each and every one of you.
I am truly hoping somebody can help me find the solution soon.

Thanks again for your help!

I will try those PIDs to see if that may be the issue.
Thanks again
Welcome to the wonderful world of engineering. We're (most of us) are bald for a reason. :D

Try switching it to PCM, anyways, just to test it. While the ensemble may be functioning, the pass through may not be.
Do you have a ASI stream analyzer? (If you don't, you should get one in this day and age). If you can get your hands on one, grab a screen shot of the output table of the encoder from the analyzer. Sometimes there could be something as stupid as the encoder is inserting a ghost pid or something that is incompatible.
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grich
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Re: some viewers Can't hear our audio

Post by grich » Tue Jan 22, 2013 7:54 am

NECRAT wrote:
Welcome to the wonderful world of engineering. We're (most of us) are bald for a reason. :D
I still have most of my hair, but I'm working on it. :D

Gotta love digital TV.

If you do have to make some big PID changes, you'll probably have to talk a few people through rescanning their receivers. What fun!

rburleson
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Re: some viewers Can't hear our audio

Post by rburleson » Tue Jan 22, 2013 11:17 am

No luck on changing the PIDs.. :(
unfortunately I don't have an ASI analyzer. How much do they cost and which one would you recommend?
We are on a very tight shoestring budget here.

rburleson
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Re: some viewers Can't hear our audio

Post by rburleson » Tue Jan 22, 2013 11:20 am

AV3 VIDEO AUDIO INTERCONNECT 1-20-13.pdf
(1.29 MiB) Downloaded 225 times
This is our set up.

w4cl
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Re: some viewers Can't hear our audio

Post by w4cl » Tue Jan 22, 2013 2:31 pm

Sencore DTU-245-SXP will do everything but decode a raw 1.5Gb HD video stream. They are around $3500 depending on options. I have one and so far I haven't found a situation where it hasn't worked when dealing with ASI streams, terrestrial or satellite. Everyone should have one.

w9wi
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Re: some viewers Can't hear our audio

Post by w9wi » Tue Jan 22, 2013 4:16 pm

There's a lot to be said for the full analyzers. (We have the Triveni MT-40)

If something like that is beyond your budget I'd get your hands on a copy of TSReader. There's a "Lite" version that's free and works with inexpensive off-the-shelf TV tuner cards/USB tuners for OTA monitoring. Even the Professional version is only $400, and it does support ASI input cards. (I've not tried either the Professional version or the ASI card) http://www.tsreader.com/legacy/

I think NECRAT has the right idea, really you're kinda flying blind without *some* way of looking at the stream. Oh, I don't see anything suspicious in your wiring diagram -- but really, whatever's going wrong is going wrong in the Titan or possibly the PCIM-1300.
--
Doug Smith W9WI
Pleasant View, TN EM66

Carmine5
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Re: some viewers Can't hear our audio

Post by Carmine5 » Mon Sep 08, 2014 7:51 pm

OK, I had the same problem and it took me months to figure out. Viewers were complaining that they were seeing the picture but no audio. I knew my encoder was pumping out AC-3 and should, therefore, have been compatible with all recent ATSC tuners. I tried every configuration on the encoder available to it as well as a variety of hex/decimal combinations up to see if the problem would clear up. It didn't. In frustration, I got a Hauppauge USB tuner and a copy of TS Reader Lite just to see what information was in my transport stream and how it compared with other stations.

Here's what I found: I looked at the TVCT PID info and under Service Location Descriptor for audio it said, "Stream Type (0x01 MPEG 1 audio)" even though my encoder was set to encode AC-3. I immediately complained to the encoder manufacturer and sent screen grabs. A few days later they sent me a firmware patch. I installed the new firmware and rechecked my transport stream. Now under Service Location Descriptor for audio it said, " Stream Type (0x81 AC-3 Audio)". Better still, viewers were now reporting that they were hearing the audio.

So, my advice to you, and others have said it as well is: get a USB tuner and a copy of TS Reader Lite and look at your transport stream, particularly the TVCT PID info. If it doesn't say that you're outputting AC-3 then you need to contact the encoder manufacturer and ask for a remedy. ATSC tuners need to see that identification to correctly decode the audio.

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