# From Dish: Technical Discussion of current P284 Issues



## Mark Lamutt (Mar 24, 2002)

The following text is from one of Jason's 811 team engineering contacts at Dish Network, discussing the current bugs in P284 on a technical level. I'm posting this for Jason, as he's currently tied up with a work issue out of the country.

From Dish:

*1. Black Screens* - It is believed that the majority of this problem is related to the occasional improper start of the MPEG decoder when changing channels. P284 has a fix for one of the three known ways this can occur in the code and which was believed to be the most prevalent. It usually was kicked off as an error when tuning between off-air and satellite. You can sometimes get the same thing to occur with different looking screens than black. Expect to see fixes for the rest of the known ways it can occur in P286.

*2. Flicker of OTA DTV or satellite HD channels* - There has been work on some improvements of the way the MPEG decoder processes errors in the stream corrupting the group of pictures (GOP) as this appears to be the cause of flicker or stutter. If the broadcaster has some variations in their GOP structure for which we are not prepared, the reaction of the decoder can be a visual affect of stutter to the next I-frame. If this occurs but is corrected by some action such as selecting another channel and then returning to the problem channel, it would be helpful to know that. Some test streams have been captured which allows the re-creation of the error and supports work on a solution with the vendor of the chip set.

*3. OTA PSIP processing* - There is a lot of confusion on how the DTV channel data in their PSIP is handled. If someone is interested in the deep details of Program and System Information Protocol (PSIP) data, they might want to download a copy of the ATSC document A/69. PSIP is a combination of a lot of types of data which each type called a "table" in the structure. The major four are the System Time Table (STT), Rating Region Table (RRT), Master Guide Table (MGT) and Virtual Channel Table (VCT). The VCT is also referred to as the Terrestrial Virtual Channel Table or TVCT. These tables contain data critical to reception as well as a lot of optional data that may or may not be included by every broadcaster. Many broadcasters are still learning how to properly set up their PSIP and may have only the minimum data in their current streams or may have conflicting data in various tables that can be ignored by some receivers but not by all. A couple of other key tables to know about are the Program Association Table (PAT) and Program Map Table (PMT). There is suppose to be a unique parameter in each broadcaster's stream called the Transport Stream ID (TSID) which is basically the only value required (currently) to be correct by the Federal Communications Commission (FCC). The ATSC standard is primarily a recommendation rather than a requirement as viewed by the FCC. Some new restrictions regarding required provision of event data and other items such as 708 closed captioning kick in the near future but it is expected to take a long time to get this working well in all broadcaster's streams.

The 811 receiver processes the tables in the PSIP when a station is scanned in and also when it is tuned. The first processing lets it find the Major and Minor Channel IDs to determine how to place the channel and subchannels in the guide. The TSID is found to identify the channel for program guide information and check for conflicts. When the channel is tuned, the tables are also processed and compared. This is typically where a conflict can show up as a problem for the customer. If the values for the Major Channel ID in various tables do not match, then the 811 will change the position in the guide and use the RF channel number (which is the only guaranteed number to be unique in that broadcast area) as the major channel identifier. Sometimes an illegal value will be encountered so the 811 will attempt to place the channel in the guide at the RF channel number so long as it can resolve the conflict or error. Most broadcasters with a problem do not appear to create that problem intentionally, they simply haven't identified the problem and the fix yet. This is made more difficult by some terrestrial tuner set top receivers that are ATSC tuners only which ignore most of the PSIP data so the broadcaster monitoring with them is not even aware of the problem. Those tuners can ignore much of the PSIP because they don't have to integrate the channel into a guide with other channels from satellite or other DTV broadcasters.

While the receiver is tuned to a DTV channel, the PSIP is monitored to look for any change in the PAT and PMT. The most common change is when a broadcaster adds or removes a minor channel (sub channel) from their stream. Since the only stream that contains this data is the one from the broadcaster, the 811 can only know about a change AFTER it tunes to the stream. Thus if a subchannel is tuned that no longer exists, it cannot be known until an existing major/minor channel pair of that same broadcaster is tuned or until the channel is scanned again.

It is important to remember that the 811 receiver can only process data from one of the tuners at a time and from only the stream to which that tuner is tuned. Thus if you are tuned to one off-air channel and some other channel changes their PSIP data, the receiver cannot know about it until tuned to that station. The receiver cannot process data from the satellite while it is tuned to an off-air channel.

Most broadcasters are not yet populating their Event Information Tables (EIT) in the MGT. And of the few who are providing that data, many are not formatting it correctly. The 811 receiver obtains all of it's program guide from the system information in the satellite data stream. It will currently ignore the EIT in the DTV broadcaster's stream. Broadcaster's provide their program schedule for broadcasts which is included in the Network Information Tables (NIT) in the satellite transmissions. A system of matching the broadcaster's TSID to data in the NIT allows the presentation of local station guide data. If the broadcaster does not provide unique data for their minor (sub) channel broadcasting structure, the same data as that broadcaster's analog station event information is used for minor channel 01 in the guide.

The industry is still maturing and the accuracy of the guide data will improve. Additional stations will be included in the guide data and new options will be offered for accessing data as the reliability of that data improves.

The satellite distributed guide data is stored in memory in the receiver when it is tuned to a satellite broadcast. There is a structure of both near term program information called Event Information Tables Present/Following (EIT-PF) and also longer term EIT. Broadcast schedules may change and memory is also limited which requires that the guide information be obtained on a frequent basis to prevent it from becoming stale and inaccurate. If the receiver is tuned away from satellite for longer than about 6 hours, it will require time to download a complete two day guide for update once tuned back to a satellite broadcast or attempting to access the guide. Exiting from a guide download will result in absence of information or corruption of the guide data. The guide is also downloaded when the receiver is in the "standby" state which is whenever it it plugged in but powered off. For this reason, it is good practice to simply turn off the receiver when not in use to maximize the reliability of the guide data. If tuned to a DTV channel but turned off, the receiver will tune back to the satellite data stream during that time to acquire guide and other data.

*4. Dolby Compatibility* - There are many rumors and suppositions about the relatively few problem cases of Dolby system compatibility with the 811. This compatibility problem affects some, but not all manufacturing dates of certain models of Dolby home theater sound systems. Since compatibility testing with some samples of the same model of home theater unit have shown the some dates of manufacture work and others don't, it appears that the bill of materials may change in run of manufacture and the firmware or chip sets used may differ. The problem exists as at least two known ways. The first has been tracked down to a compatibility bit setting in the SPDIF header. A fix for that condition is contained in P285 software. But that does not fix compatibility with all Dolby receivers. It appears that some other header information is not yet correct and that while most Dolby receivers ignore the header issue, some are confused by it. Even the Dolby Labs test procedures do not catch either of these two problems which has complicated the diagnosis and solution. If this is correct, the solution will be found but the isolation in testing and correction is difficult. The fix would come as a driver change working with the chip set vendor and sent as a software update in a future release. A lot of pressure is on to find the remaining conflict and correct it. In the short term, if a Dolby receiver does not connect after P285 is released, the PCM only mode should be tried as a temporary fix.

Copyright Jason Nipp and DBSTalk


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## Broadband Lab Rat (Nov 4, 2003)

RE: Flicker

My occurances of flicker always occur on OTA HD channels. Tuning to another OTA HD channel, and then back to the problem channel will *sometimes* clear it... however tuning to a SD sat channel, and then back to the problem channel, always clears it for me.


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## SRW1000 (Feb 22, 2004)

Mark,

Thanks for posting this. I've copied the Dolby Digital part of the discussion over to the Dolby Digital thread.

Scott


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## Mark Lamutt (Mar 24, 2002)

You bet, Scott, although Jason really is the one that deserves the thanks. I'm just the messanger on this one.


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## Ron Barry (Dec 10, 2002)

This is some good stuff. Thanks Jason for working with Dish and thanks Mark. THis is some great stuff and info.


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## Pils (Sep 20, 2004)

Is it possible to have a list of OTA channels and what numbers they remap to on the 811? I am curious if all 811s in my city remap to the same channel or does it vary by the type of antenna on the house? A E* engineer told me the antenna determined how the PSIP was interpretted but seems quite fishy. Anyways, just curious because I can scan channels and have them correct and then they remap once I go to the channel. Delete this message if in wrong forum or whatever. Thanks.


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## Pils (Sep 20, 2004)

Another issue I had was my P284 froze on a OTA station. The stations video and audio was fine, but when I used the remote to change stations, it would not respond. Not even the menus, etc and the front pannel so I had to reboot with power button held down. Anyone else experience this, had it happen twice?


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## Mark Lamutt (Mar 24, 2002)

Pils, I can't help you with your second question, but all 811s will map your local channels exactly the same way, regardless of antenna, as long as your antenna picks up the local station's signal. 

If the channels change mapped channels when you tune to them, read the PSIP section in the above document. It means that there's a problem with the station's tables that they're sending in their broadcast stream.


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## Ron Barry (Dec 10, 2002)

Pils said:


> Is it possible to have a list of OTA channels and what numbers they remap to on the 811? I am curious if all 811s in my city remap to the same channel or does it vary by the type of antenna on the house? A E* engineer told me the antenna determined how the PSIP was interpretted but seems quite fishy. Anyways, just curious because I can scan channels and have them correct and then they remap once I go to the channel. Delete this message if in wrong forum or whatever. Thanks.


I would be very suprised the antenna determines how PSIP is interperted. That would mean you would have to get a certain antenna for a particular area. From my understanding PSIP is defined standard protocal embedded in the stream and part of it is channel mapping info. This would be consistent for all users that are receiving the signal.

As to getting a list of channels and what they remap to. I don't know of one. You should be able to get an idea of the mapping by using antennaweb.org and manually add channels noting the mapping that occurs when you add it. I know this is manual but it will giv eyou and idea.

As to channels getting remapped to their frequecy and sometime disappearing and reappearing. Based on my experience, I think this is related to signal quality issues and possible difference in PSIP stream data and how the 811 may interperate it. Just become something is a standard, there is the interpertation of the standard and that is where bugs crop up. I have seen it throughout my career.


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## moman19 (Oct 22, 2004)

WHile on the subject of mapping, my local PBS afilliate broadcast three sub-channels. 01 is HD, 02 os kids programming 24 X 7 and 03 is a mirror (in SD) of the analog station. All Guide data for 03 always appears under 02.

I've written about this annoyance before in another thread, but I hope that eyes at Echostar may be reading these posts and taking our data more seriously.


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## baumane (Aug 17, 2002)

Pils said:


> Is it possible to have a list of OTA channels and what numbers they remap to on the 811? I am curious if all 811s in my city remap to the same channel or does it vary by the type of antenna on the house?


I think the link below may help you out. Put in your address/zip code and it will list the stations in your area. All my local hd station frequencies map to the channels as listed. I use the frequency listing to manually program my 811 when the auto scan does not pick up all.

http://www.antennaweb.org/aw/address.aspx

etb


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## Cholly (Mar 22, 2004)

moman19 said:


> WHile on the subject of mapping, my local PBS afilliate broadcast three sub-channels. 01 is HD, 02 os kids programming 24 X 7 and 03 is a mirror (in SD) of the analog station. All Guide data for 03 always appears under 02.
> 
> I've written about this annoyance before in another thread, but I hope that eyes at Echostar may be reading these posts and taking our data more seriously.


Don't blame Echostar for this, blame the station for not transmitting their PSIP data correctly. Read Mark's post at the beginning of this thread carefully. Echostar transmists the PSIP data they receive. If none is there for the subchannels, it will either post No Data or mirror the data from the primary.


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## astrotrf (Apr 5, 2004)

It sounds to me like there's a market for a piece of software to read a station's PSIP information and do syntax and consistency checking. It's pretty obvious that a fair number of broadcasters need this.

Terry


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## moman19 (Oct 22, 2004)

Cholly said:


> Don't blame Echostar for this, blame the station for not transmitting their PSIP data correctly. Read Mark's post at the beginning of this thread carefully. Echostar transmists the PSIP data they receive. If none is there for the subchannels, it will either post No Data or mirror the data from the primary.


Cholly,

Your response conflicts with what I've been told by others.

1. I think it was WJD who stated that -02 is the hard-coded alternative channel for the mirror when it is not -01. In this case the mirror should be -03.

2. I am in direct communication with the Chief Engineer of the TV station who says that he monitors his station on 4 different HD STB receivers (Samsung, RCA, Panasonic and Zenith) and was completely unaware of this issue until I pointed it out to him...which he confirmed. It only seems to be an issue on the 811.

So I doubt there is a PSIP issue in this case. The 811 still seems "guilty" to me.


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## Pils (Sep 20, 2004)

I agree the 811 is guilty as well. I have a tv HD tuner that registers perfectly and a couple neighbors with the D* HD receivers that register channels perfectly.


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## Ron Barry (Dec 10, 2002)

moman19 said:


> Cholly,
> 
> Your response conflicts with what I've been told by others.
> 
> 1. I think it was WJD who stated that -02 is the hard-coded alternative channel for the mirror when it is not -01. In this case the mirror should be -03.


Nope not me. But it was stated.



moman19 said:


> 2. I am in direct communication with the Chief Engineer of the TV station who says that he monitors his station on 4 different HD STB receivers (Samsung, RCA, Panasonic and Zenith) and was completely unaware of this issue until I pointed it out to him...which he confirmed. It only seems to be an issue on the 811.
> 
> So I doubt there is a PSIP issue in this case. The 811 still seems "guilty" to me.


Possibly. But It depends on the PSIP spec. It could be one of these interpertation type issues that are very common with Standards.


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## Ron Barry (Dec 10, 2002)

Pils said:


> I agree the 811 is guilty as well. I have a tv HD tuner that registers perfectly and a couple neighbors with the D* HD receivers that register channels perfectly.


What do you mean by Registers? Is your problem the exact same problem or different than moman? If it is different, It sounds like you got a good handle on it and I would report it as a bug. Don't think I saw it.


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## jimpat (Nov 15, 2003)

I am in the DFW area before the 284 update my main digital stations were FOX-4.1
NBC-5.1 ABC-8.1 AND CBS-11.1 Now they are listed as 19.1,41.1, 8.1, and 35.1. All but 8 changed. I followed forum information and removed all from the local listings and then did a hard reboot (puled the plug). I then did another didital scan and nothing changed. IS the problem my 811 or 284?


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## moman19 (Oct 22, 2004)

jimpat said:


> I am in the DFW area before the 284 update my main digital stations were FOX-4.1
> NBC-5.1 ABC-8.1 AND CBS-11.1 Now they are listed as 19.1,41.1, 8.1, and 35.1. All but 8 changed. I followed forum information and removed all from the local listings and then did a hard reboot (puled the plug). I then did another didital scan and nothing changed. IS the problem my 811 or 284?


When you deleted all locals did you also remember to remove them from any custom FAVORITES lists? Remove them from your FAVORITES first, then delete all locals, rescan them in and finally, rebuild your FAVORITES lists. This is how it worked for me.


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## jimpat (Nov 15, 2003)

Yes I did it the same as you, but it now only shows the mapping numbers.


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## Cholly (Mar 22, 2004)

Moman19: My bad -- I may have misinterpreted something I read about PSIP and in particular, digital mirrors of analog stations. In my area, the mirror of my PBS station has shown up as -2. I can't comment further on accuracy of PSIP info, since we don't have LIL in my DMA.


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## Nick (Apr 23, 2002)

moman19 said:


> I am in direct communication with the Chief Engineer of the TV station who says that he monitors his station on 4 different HD STB receivers (Samsung, RCA, Panasonic and Zenith) and was completely unaware of this issue until I pointed it out to him...which he confirmed. It only seems to be an issue on the 811.
> 
> So I doubt there is a PSIP issue in this case. The 811 still seems "guilty" to me.





Pils said:


> I agree the 811 is guilty as well. I have a tv HD tuner that registers perfectly and a couple neighbors with the D* HD receivers that register channels perfectly.


Well, there goes *that* excuse!

Why does EchoStar insist on reinventing the wheel and where in the world do those oddball non-conforming standards come from anyway? :shrug:

Truth is, like Dish itself, their gear doesn't always play well with others.


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## jimpat (Nov 15, 2003)

This morning when I checked the guide all the stations are showing the correct call numbers. It fixed its self.


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## Pils (Sep 20, 2004)

WeeJavaDude said:


> What do you mean by Registers? Is your problem the exact same problem or different than moman? If it is different, It sounds like you got a good handle on it and I would report it as a bug. Don't think I saw it.


What I mean is that on the other sources, 11.1, 11.2, 11.3 all show up as that channel number. But on the 811, 11.1 goes to 35.01 and 11.2 is 35.02 and 11.3 I have no clue, think it is completely gone. And the signal strength is stronger on these other tuners, I don't have dropouts because it can't lock on. The 811 has a hell of a time holding in our Fox HD but the tv tuner never drops signal.


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## Ron Barry (Dec 10, 2002)

Pils said:


> What I mean is that on the other sources, 11.1, 11.2, 11.3 all show up as that channel number. But on the 811, 11.1 goes to 35.01 and 11.2 is 35.02 and 11.3 I have no clue, think it is completely gone. And the signal strength is stronger on these other tuners, I don't have dropouts because it can't lock on. The 811 has a hell of a time holding in our Fox HD but the tv tuner never drops signal.


I am assuming you mean by other tuners you TV tuner?

It is my understanding that the 811 signal strength meter is a ratio of signal strength and errors. It just does not indicate signal strength.

I am confused. You are saying that the 811 can't lock but then you say it has a hard time holding it.? The 811 is more sensitive to multipathing than other tuners so that might be the issue. Hard to say. Also could be related to the 811 not being able to interpert PSIP channel information properly.


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## Pils (Sep 20, 2004)

WeeJavaDude said:


> I am assuming you mean by other tuners you TV tuner?
> 
> It is my understanding that the 811 signal strength meter is a ratio of signal strength and errors. It just does not indicate signal strength.
> 
> I am confused. You are saying that the 811 can't lock but then you say it has a hard time holding it.? The 811 is more sensitive to multipathing than other tuners so that might be the issue. Hard to say. Also could be related to the 811 not being able to interpert PSIP channel information properly.


Yes, I mean my sony built in tv tuner. I am saying that it will not lock when I turn to the channel, so I channel up and then back to the same channel until it will finally lock. Then while watching, it will lose the signal again. But if I switch to the tv tuner, the channel will lock right away and not lose its signal. On the 811, it only sits at 49% and if i can get it to lock, it is 80. I know the signal is not 49%.


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## NightRyder (Jan 29, 2004)

Mark Lamutt said:


> The following text is from one of Jason's 811 team engineering contacts at Dish Network, discussing the current bugs in P284 on a technical level. I'm posting this for Jason, as he's currently tied up with a work issue out of the country.
> 
> From Dish:
> 
> ...


In my experience the stutter happens mainly on TNT-HD but I have seen the problem on DSC-HD and CBS-HD. Even if the stutter self corrects I have to change the channel or cycle the power to re-sync the audio and video.

NightRyder


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