Mailing List Archive: MythTV: Users

QAM Channel Scanner

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larryt at gmail

Aug 6, 2008, 12:11 PM

Post #1 of 5 (385 views)
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QAM Channel Scanner

I have been using a pcHDTV 5500 for approximately 3 years and I remember
there was a period where scanning worked for some people and didn't work for
others. Then a release came out and corrected the problems.

Since then, it had been working until a few weeks ago. A few weeks ago, I
stopped being able to tune in to channels that I used to have. I rescanned
using mythtvsetup and was unable to find the channels. My total QAM channels
had diminished by approximately 2/3. I scanned with my TV with QAM tuner and
the missing QAM channels were still present (though not remapped). Thinking
I had signal problems, I brought a cable tech out and boosted my signal
which did not help. Thinking my tuner had gone bad or was not sensitive
enough, I purchased a HDHomerun which gave me new insight.

To illustrate my problem, I will focus on my local CBS HD affiliate which is
105.2 according to
http://www.silicondust.com/hdhomerun/lineupui?Cmd=LocationProgramsWeb&Country=US&Postcode=32904.
Both the 5500 and HDHR when scanning through MythTV detect the 105 range and
lock on, then report it as "No Tables" and do not add any subchannels in
that range. They do not give any further details about the subchannels.
There is no indication of failing to tune or encrypted channel or anything
else as to why 105.x is not identified. It jumps to 106 in which it reports
a lot of encrypted channels. If I use my TV QAM tuner or the HDHR Windows
based software, I can locate every QAM channel in the above link. The
channels lock on and stream fine with a reasonable signal.

My settings for the scan appear to be reasonable because I do receive some
channels such as those in the 50 and 76 range of the above link. Is this a
known issue with a workaround such as manually adding the channels? Is there
any way to increase the relevant logging in mythtvsetup to provide more
detailed information? Thanks for any help.

mythtv at cox

Aug 6, 2008, 8:39 PM

Post #2 of 5 (355 views)
Permalink

Re: QAM Channel Scanner [In reply to]

Larry T wrote:
> I have been using a pcHDTV 5500 for approximately 3 years and I
> remember there was a period where scanning worked for some people and
> didn't work for others. Then a release came out and corrected the
> problems.
>
> Since then, it had been working until a few weeks ago. A few weeks
> ago, I stopped being able to tune in to channels that I used to have.
> I rescanned using mythtvsetup and was unable to find the channels. My
> total QAM channels had diminished by approximately 2/3. I scanned with
> my TV with QAM tuner and the missing QAM channels were still present
> (though not remapped). Thinking I had signal problems, I brought a
> cable tech out and boosted my signal which did not help. Thinking my
> tuner had gone bad or was not sensitive enough, I purchased a
> HDHomerun which gave me new insight.
>
> To illustrate my problem, I will focus on my local CBS HD affiliate
> which is 105.2 according to
> http://www.silicondust.com/hdhomerun/lineupui?Cmd=LocationProgramsWeb&Country=US&Postcode=32904
> <http://www.silicondust.com/hdhomerun/lineupui?Cmd=LocationProgramsWeb&Country=US&Postcode=32904>.
> Both the 5500 and HDHR when scanning through MythTV detect the 105
> range and lock on, then report it as "No Tables" and do not add any
> subchannels in that range. They do not give any further details about
> the subchannels. There is no indication of failing to tune or
> encrypted channel or anything else as to why 105.x is not identified.
> It jumps to 106 in which it reports a lot of encrypted channels. If I
> use my TV QAM tuner or the HDHR Windows based software, I can locate
> every QAM channel in the above link. The channels lock on and stream
> fine with a reasonable signal.
>
> My settings for the scan appear to be reasonable because I do receive
> some channels such as those in the 50 and 76 range of the above link.
> Is this a known issue with a workaround such as manually adding the
> channels? Is there any way to increase the relevant logging in
> mythtvsetup to provide more detailed information? Thanks for any help.
> ------------------------------------------------------------------------
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users[at]mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
I have the same problem. Attached is my solution. Put your QAM data
into the CSV file (keep the columns in the same order). Then run the
script. The script will rename existing channels and insert missing
channels.

No guarantees or refunds. Send back if you make it better.

Bob

Attachments:

cox_qam.csv (1.81 KB)

fix_qam.pl (3.50 KB)

larryt at gmail

Aug 7, 2008, 8:35 AM

Post #3 of 5 (341 views)
Permalink

Re: QAM Channel Scanner [In reply to]

Thank you very much Bob. I fiddled with the CSV file a bit. Also, I found
that your frequency calculator was not generating the appropriate
frequencies for my cable so I modified your script to pull the frequencies
in instead of freqID. Then I searched for the mplexID by the frequencies. To
accommodate this, I also skipped the check for an existing channel. Maybe
this was a result of my misunderstanding of your script. Either way, I am
not sure this constitutes an improvement because your version was more
comprehensive.

In summary, Bob's script (which directly adds channels to the db) fixed two
problems for me that may or may not be related:
1) Many of my digital SD channels were coming in and being assigned to 1008
thus leaving me with only one of those channels at the end of the import of
channels.conf or scan. These channels were tuning fine though.
2) I was not able to tune some digital channels through an import or scan.
This allowed me to directly add those channels and I have verified they
function by recording programming on these channels and viewing the .mpg
captured.

In an effort to improve MythTV, are these problems the result of a software
bug somewhere in the chain or a misconfiguration on my part? Any guesses?

On Wed, Aug 6, 2008 at 11:39 PM, Bob <mythtv[at]cox.net> wrote:

> Larry T wrote:
>
>> I have been using a pcHDTV 5500 for approximately 3 years and I remember
>> there was a period where scanning worked for some people and didn't work for
>> others. Then a release came out and corrected the problems.
>>
>> Since then, it had been working until a few weeks ago. A few weeks ago, I
>> stopped being able to tune in to channels that I used to have. I rescanned
>> using mythtvsetup and was unable to find the channels. My total QAM channels
>> had diminished by approximately 2/3. I scanned with my TV with QAM tuner and
>> the missing QAM channels were still present (though not remapped). Thinking
>> I had signal problems, I brought a cable tech out and boosted my signal
>> which did not help. Thinking my tuner had gone bad or was not sensitive
>> enough, I purchased a HDHomerun which gave me new insight.
>>
>> To illustrate my problem, I will focus on my local CBS HD affiliate which
>> is 105.2 according to
>> http://www.silicondust.com/hdhomerun/lineupui?Cmd=LocationProgramsWeb&Country=US&Postcode=32904<
>> http://www.silicondust.com/hdhomerun/lineupui?Cmd=LocationProgramsWeb&Country=US&Postcode=32904>.
>> Both the 5500 and HDHR when scanning through MythTV detect the 105 range and
>> lock on, then report it as "No Tables" and do not add any subchannels in
>> that range. They do not give any further details about the subchannels.
>> There is no indication of failing to tune or encrypted channel or anything
>> else as to why 105.x is not identified. It jumps to 106 in which it reports
>> a lot of encrypted channels. If I use my TV QAM tuner or the HDHR Windows
>> based software, I can locate every QAM channel in the above link. The
>> channels lock on and stream fine with a reasonable signal.
>>
>> My settings for the scan appear to be reasonable because I do receive some
>> channels such as those in the 50 and 76 range of the above link. Is this a
>> known issue with a workaround such as manually adding the channels? Is there
>> any way to increase the relevant logging in mythtvsetup to provide more
>> detailed information? Thanks for any help.
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> mythtv-users mailing list
>> mythtv-users[at]mythtv.org
>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>>
>>
> I have the same problem. Attached is my solution. Put your QAM data into
> the CSV file (keep the columns in the same order). Then run the script.
> The script will rename existing channels and insert missing channels.
>
> No guarantees or refunds. Send back if you make it better.
>
> Bob
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users[at]mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
>

elektron at gmail

Aug 7, 2008, 9:55 AM

Post #4 of 5 (342 views)
Permalink

Re: QAM Channel Scanner [In reply to]

On Thu, Aug 7, 2008 at 8:35 AM, Larry T <larryt[at]gmail.com> wrote:

> In an effort to improve MythTV, are these problems the result of a software
> bug somewhere in the chain or a misconfiguration on my part? Any guesses?
>
>
I am in long beach california on charter cable and have this same problem.
It seems to be the cable provider. I did some investigation and it appears
the cable company is sending 0 for both the atsc minor and major channel
numbers in the VCT tables. mythtv freaks out with these because it appears
there are multiple program numbers that map to the same channel. I wouldn't
necessarily blame mythtv for this, because it looks like a deviation from
the standard on the cable companies part.

I modified my source tree to ignore the VCT, and now the channel scanner
finds every channel using the the PAT (or was the PMT?), I just have to do
the manual processing of deciding which program number is which channel. I
assume there is some other multiplex with some other complete table (whether
it is a VCT or not) that has a list of all the channel numbers and program
numbers. I just haven't spent the time evaluating all the multiplexes that
my cable company provides.

Daniel is working on a new channel scanner, I am not sure if it will have
the ability to ignore broken ATSC tables or not, but I remain hopeful. :)

larryt at gmail

Aug 7, 2008, 10:51 AM

Post #5 of 5 (337 views)
Permalink

Re: QAM Channel Scanner [In reply to]

Unfortunately getting support from the cable companies does not seem like a
very viable solution. When I had a technician come out to address the
problem, he had heard of the clear QAM channels but knew nothing more and
just called it a signal problem. When I spoke to tech support on the phone
to try to get someone knowledgeable to discuss the tables, the lady told me
that they do not "do QAM" and they can't support QAM tuners. I protested so
she asked her supervisor who also did not know anything about QAM. Someone
in my local office must know what they are doing because they recently added
4 Olympics only channels that are properly tabled.

Elektron, for your channel scanning solution, take a look at the channel
pages from SiliconDust. I am very impressed with their lineups by zip codes
page. In my case, it is a very easy and accurate way to identify which
channels I should expect from the cable.

For Daniel, I am always willing to provide a data point for the new scanner
when you need testers.

On Thu, Aug 7, 2008 at 12:55 PM, elektron <elektron[at]gmail.com> wrote:

>
> On Thu, Aug 7, 2008 at 8:35 AM, Larry T <larryt[at]gmail.com> wrote:
>
>> In an effort to improve MythTV, are these problems the result of a
>> software bug somewhere in the chain or a misconfiguration on my part? Any
>> guesses?
>>
>>
> I am in long beach california on charter cable and have this same problem.
> It seems to be the cable provider. I did some investigation and it appears
> the cable company is sending 0 for both the atsc minor and major channel
> numbers in the VCT tables. mythtv freaks out with these because it appears
> there are multiple program numbers that map to the same channel. I wouldn't
> necessarily blame mythtv for this, because it looks like a deviation from
> the standard on the cable companies part.
>
> I modified my source tree to ignore the VCT, and now the channel scanner
> finds every channel using the the PAT (or was the PMT?), I just have to do
> the manual processing of deciding which program number is which channel. I
> assume there is some other multiplex with some other complete table (whether
> it is a VCT or not) that has a list of all the channel numbers and program
> numbers. I just haven't spent the time evaluating all the multiplexes that
> my cable company provides.
>
> Daniel is working on a new channel scanner, I am not sure if it will have
> the ability to ignore broken ATSC tables or not, but I remain hopeful. :)
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users[at]mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
>

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