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Major Audio Stuttering During Grammys!!


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19 replies to this topic

#1 OFFLINE   pappasbike

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Posted 12 February 2007 - 11:33 AM

We were watching the Directv local HD broadcast on the local CBS affiliate WJZ 13 in Baltimore. I've never heard it this bad on any station. At one point it was almost continuous like a lawn mower running. I emailed and received a reply from the station's engineer and of course he watched the ota broadcast and saw no problem. He stated that he did not know how Directv picked up their HD channel. I also went to Dirctv's web site and sent a message with this info. But I hope they can make an effort to resolve this with the locals because lately in the Baltimore area the problem has gotten significantly worse. I know it's supposed to be an issue with the broadcaster but I'm wondering if the receiver has some thing to do with it.
John

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#2 OFFLINE   Sickler

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Posted 12 February 2007 - 11:46 AM

I also experience occasioanl audio drop outs during commercials again (exactly like the Super Bowl). I just did a quick replay to watch it buffered and no longer had any audio drop outs. This was with the local CBS MPEG4 broadcast in Los Angeles.

#3 OFFLINE   pappasbike

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Posted 12 February 2007 - 12:00 PM

Just got a reply from the station engineer. He received a reply from someone at CBS( I believe). I'm posting this below.

>>
Greetings,

This is no surprise. All of our testing has shown that MPEG-4 is not
reaching the 2:1 compression efficiency that has been claimed. DirecTV
is pre-filtering your over-the-air signal and not providing enough bits
on the satellite to preserve the original image quality. A class action
suit has been filed against DirecTV regarding their MPEG-4 local into
local quality.

My only suggestion is for them to install an over-the-air antenna and
connect it to the DirecTV box rather than relying on the MPEG-4 local
into local service on the satellite.

When the MPEG-4 encoder manufacturers demonstrate these reduced bit
rates, they used soft film based content, which is less stressful on the
system and NOT typical of live Sports, Award shows, and electronically
captured high definition content. Rapid camera motion and dramatic
scene lighting - such as the Grammy Awards - stress the compression
system beyond its limits.

Bob Seidel
Director of Advanced Technology
CBS <<

#4 OFFLINE   HockeyKat

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Posted 12 February 2007 - 12:05 PM

Oh yeah, WJZ was absolutely horrible last night. We had to switch to OTA in order to hear anything. Although the weird audio noises were better than the Shakira performance. lol

I like how they're blaming DTV when they're the ones suddenly having such issues. I've never seen it as bad as it was last night. Now their station is having issues and it's DTV's fault? hhmmm... And yet the guy from WBFF (45) was aware of the issue, constantly working to correct it, and overall very helpful.

#5 OFFLINE   Earl Bonovich

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Posted 12 February 2007 - 12:06 PM

Can you write the station manager back, and ask him for a link or docket number or some sort of source, for the Class Action law suit, with regards to the MPEG-4. As that is the first I have heard of one. (I have heard of the one with regards to the MPEG-2)

I don't know how Baltimore is setup...
But in a lot of cases, DirecTV is getting the HD signal via OTA...
So it is getting it from a source that is already compressed, and "altered"...
So it is already "disconnected" from the "origianl image quality".

So by definition of the compression algorithms, in this case... MPEG-4 would be lower quality then MPEG-2.

And also, ask him where it was claimed to be a 2:1 efficiency.
As even by the "numbers" on the HR20, it is not 2:1 (50 hrs MPEG-4, 30 hrs MPEG-2)
Earl - Gotta Love Karma

DIRECTV employee since April 2008.
All comments are my own. Unless specifically stated, my views do NOT represent the views of DIRECTV

#6 OFFLINE   bnglbill

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Posted 12 February 2007 - 12:28 PM

When the MPEG-4 encoder manufacturers demonstrate these reduced bit
rates, they used soft film based content, which is less stressful on the
system and NOT typical of live Sports, Award shows, and electronically
captured high definition content. Rapid camera motion and dramatic
scene lighting


This makes perfect sense, now that I think about it , it is worse during live events such as American idol.
Bill
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#7 OFFLINE   pappasbike

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Posted 12 February 2007 - 12:32 PM

Can you write the station manager back, and ask him for a link or docket number or some sort of source, for the Class Action law suit, with regards to the MPEG-4. As that is the first I have heard of one. (I have heard of the one with regards to the MPEG-2)

I don't know how Baltimore is setup...
But in a lot of cases, DirecTV is getting the HD signal via OTA...
So it is getting it from a source that is already compressed, and "altered"...
So it is already "disconnected" from the "origianl image quality".

So by definition of the compression algorithms, in this case... MPEG-4 would be lower quality then MPEG-2.

And also, ask him where it was claimed to be a 2:1 efficiency.
As even by the "numbers" on the HR20, it is not 2:1 (50 hrs MPEG-4, 30 hrs MPEG-2)

Earl, I just emailed him with a link to this thread and hopefully he can take a look and respond to your questions. I don't think I'm the one to phrase them correctly. But the comment from CBS does not leave optimistic about Directv's future mpeg4 offerings.
John

#8 OFFLINE   Earl Bonovich

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Posted 12 February 2007 - 12:40 PM

Earl, I just emailed him with a link to this thread and hopefully he can take a look and respond to your questions. I don't think I'm the one to phrase them correctly. But the comment from CBS does not leave optimistic about Directv's future mpeg4 offerings.
John


That comment was from one CBS affiliate, so let's not go condemming DirecTV's MPEG-4 offerings just yet.... A lot is going to change in 2007, especially when/if the new SATs successfully launch.
(I hate having to inlcude IF in that statement, but it is what it is)

"Locals" and "Networks" are two different beasts that DirecTV has to deal with. Different dynamics in each case... and with-in the Locals, each affiliate is different from the next.

Like here in Chicago... The MPEG-4's at least on my TV, with my eyes... are just as good as the OTA... I wouldn't say they are better... but they are not noticeable worse (in general, as there are sometimes when there have been issues).
Earl - Gotta Love Karma

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All comments are my own. Unless specifically stated, my views do NOT represent the views of DIRECTV

#9 OFFLINE   pappasbike

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Posted 12 February 2007 - 12:52 PM

That comment was from one CBS affiliate, so let's not go condemming DirecTV's MPEG-4 offerings just yet.... A lot is going to change in 2007, especially when/if the new SATs successfully launch.
(I hate having to inlcude IF in that statement, but it is what it is)

"Locals" and "Networks" are two different beasts that DirecTV has to deal with. Different dynamics in each case... and with-in the Locals, each affiliate is different from the next.

Like here in Chicago... The MPEG-4's at least on my TV, with my eyes... are just as good as the OTA... I wouldn't say they are better... but they are not noticeable worse (in general, as there are sometimes when there have been issues).

I don't have a problem with the video on these channels-I agree with you I don't see any difference watching the ota broadcast from Directv's channel. But this audio issue at least here in Baltimore is really getting old. I have my antenna connected directly to the tv to get the local HD broadcasts because the tuner on the HR20 would not pick up the same channels but my recordings are set for Directv's channels on the receiver and the audio problem is beginning to ruin them. If I'm watching live I just switch over to the tv's tuner if the audio is bad but that doesn't help the recordings.

That's what I meant by my concern for their future offerings-will there be the same audio issues with the new channels.
John

#10 OFFLINE   kehardman

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Posted 12 February 2007 - 01:00 PM

For yesterday's Georgia Tech/UConn game I recorded both the OTA and the DTV feed. When I had an audio drop during the DTV feed, I would switch over on the OTA to see if the same happened. It was not with DTV, but with the CBS feed from the Georgia Dome since the audio/video drops were on both recordings.

Just food for thought.

#11 OFFLINE   banningview

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Posted 12 February 2007 - 01:16 PM

The Grammys were terrible here as well. I spent a good 15 minutes going back and forth between MP4 and OTA. Come on now...It's not THAT tough to see the difference. I have a 42" plasma and I can see the difference. OTA looks a heck of lot better than MP4 over the sat. You can see pixelation and the occasion freeze on MP4 and a much sharper, smoother picture on OTA.
DLB
Just DO It!:grin:

#12 OFFLINE   pappasbike

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Posted 12 February 2007 - 01:28 PM

The Grammys were terrible here as well. I spent a good 15 minutes going back and forth between MP4 and OTA. Come on now...It's not THAT tough to see the difference. I have a 42" plasma and I can see the difference. OTA looks a heck of lot better than MP4 over the sat. You can see pixelation and the occasion freeze on MP4 and a much sharper, smoother picture on OTA.

I do not have a problem with the video on Directv's HD mpeg4 channels, there is that occasional breakup that you will get with any satellite broadcast HD or not. Overall I've been quite pleased with the picture quality. The problem I'm referring to is that stuttering/motor boating sound that apparently only happens on the mpeg4 HD locals. It was extremely bad during the Grammys and as someone else mentioned on Fox's American Idol. I will occasionally hear dropouts on both ota as well s from Directv, that's not the issue.
John

#13 OFFLINE   wjz-engineering

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Posted 12 February 2007 - 01:35 PM

Just so you all know how the signal flow goes at WJZ, we receive the HD signal from CBS via satellite on a Harris NetPlus digital IRD at 45 MBs Dolby E encoded. We MUX the decoded AES pairs into a baseband SMPTE 292 HDSDI signal with the 3 embedded AES pairs. After it passes through our Master Control switcher, the audio is DEMUXED from the video and fed to a Dolby 569 AC-3 encoder. The AC-3 audio signal is MUXed with the video and encoded by a Harris Unicoder to a SMPTE 310 signal at 19.2 MBs (the ATSC standard) and fed to our Harris PowerCD 77kW Transmitter. We do not use any subchannels (-2, -3, etc) so we use ALL the bits on the primary signal. It is difficult to further reduce the bitrate by compression without artifacts. I have a stream analyzer at home to see how the system is performing and I can tell you that the Grammy telecast was pushing our encoder pretty hard to keep up with the fast motion lighting and the strobe effects. The confetti falling at the end of the show was the hardest I have ever seen the encoder pushed since we started HD broadcasting.

If DirecTV expects to take our 19.2 mB signal off-air, which is how they are doing it, and tries to throw away more bits in their encoders and in the satellite transport stream when the original stream is already being "pushed" it is no wonder it "breaks" their system.

Rick Seaby
Director of Engineering
WJZ-TV

#14 OFFLINE   Michael D'Angelo

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Posted 12 February 2007 - 02:31 PM

My question is what has changed to cause these problems. I did not have any problem till about 4 weeks ago I started having problems with FOX and now I am having problems with all of them. I have had my local MPEG4 channels since June with my H20 and since September with my HR20.

#15 OFFLINE   Earl Bonovich

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Posted 12 February 2007 - 02:32 PM

My question is what has changed to cause these problems. I did not have any problem till about 4 weeks ago I started having problems with FOX and now I am having problems with all of them. I have had my local MPEG4 channels since June with my H20 and since September with my HR20.


Are you seeing the same issues on both units?
Earl - Gotta Love Karma

DIRECTV employee since April 2008.
All comments are my own. Unless specifically stated, my views do NOT represent the views of DIRECTV

#16 OFFLINE   Michael D'Angelo

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Posted 12 February 2007 - 02:38 PM

Are you seeing the same issues on both units?


I have not tried my H20. I only use that receiver for PIP now since I have had my HR20. I will try it but if it works it is really not going to help me because I do a lot of recording on my locals.

#17 OFFLINE   Earl Bonovich

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Posted 12 February 2007 - 02:41 PM

I have not tried my H20. I only use that receiver for PIP now since I have had my HR20. I will try it but if it works it is really not going to help me because I do a lot of recording on my locals.


The reason for the comparison, is if they both show the same issues.
Then it isn't the unit at your home, but at the encoding end.
Earl - Gotta Love Karma

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All comments are my own. Unless specifically stated, my views do NOT represent the views of DIRECTV

#18 OFFLINE   Michael D'Angelo

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Posted 12 February 2007 - 02:44 PM

The reason for the comparison, is if they both show the same issues.
Then it isn't the unit at your home, but at the encoding end.


Do you know what may have changed over the last month that has caused the problem to start? Before then I did not have one audio problem with them at all.

#19 OFFLINE   wjz-engineering

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Posted 12 February 2007 - 03:20 PM

I think they may have added more local HD markets to the transponder(s) prior to the Superbowl, increasing the load on their MUX and using more of the available bandwidth. We have made ZERO CHANGES to our encoding system in years. With a statistical multiplexing encoder scheme (many channels per carrier), whoever has more motion in their signal gets more of the bits (and, consequently, somebody else doesn't). If all the channels being MUX'd into a carrier have lots of motion, bright/dark scene changes and high detail at the same time, everybody on that carrier gets starved for bits and the macroblocking tango begins!. It is a bit like squeezing a water balloon....squeeze here and it bulges there, but the same amount of water is still in the total balloon. If all you have is xx MBs per second and you divide that among yy signals, you get the point.

Rick Seaby

#20 OFFLINE   bnglbill

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Posted 12 February 2007 - 08:15 PM

I think they may have added more local HD markets to the transponder(s) prior to the Superbowl, increasing the load on their MUX and using more of the available bandwidth. We have made ZERO CHANGES to our encoding system in years. With a statistical multiplexing encoder scheme (many channels per carrier), whoever has more motion in their signal gets more of the bits (and, consequently, somebody else doesn't). If all the channels being MUX'd into a carrier have lots of motion, bright/dark scene changes and high detail at the same time, everybody on that carrier gets starved for bits and the macroblocking tango begins!. It is a bit like squeezing a water balloon....squeeze here and it bulges there, but the same amount of water is still in the total balloon. If all you have is xx MBs per second and you divide that among yy signals, you get the point.

Rick Seaby


WOW, Thanks WJZ, now if we could only get a D engineer on here to tell their side of this.
Bill
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