[mythtv-users] Quick and dirty workaround

Bruce Markey bjm at lvcm.com
Wed Aug 11 20:57:58 EDT 2004

Jay R. Ashworth wrote:
> On Tue, Aug 10, 2004 at 09:35:20PM -0700, Bruce Markey wrote:
>>...yet there it is. The rules that govern what station broadcast
>>from where are moot. The point is that devices that output RF
>>normally have a a mechanism to select the output frequency and
>>the choices are suspect at best. This is why super VHS included
>>a new type of connector to get away from issues of broadcast
>>interference entirely.
> No, it *so* isn't.

1) Devices that output RF do have a mechanism to select the output

2) S-video does avoid issues of broadcast interference entirely as
you acknowledge in next two paragraphs.

Which are you saying 'no' to?

> S-video is completely unrelated to RF interconnections; *it's* job was
> to deconflict NTSC 3.58MHz subcarrier color from the luminance of a
> baseband video signal, as I noted in another posting, so that you
> didn't have to use brickwall or comb filters to do that.

That is true also. The fact that you interpret this to be more
important does not lessen the fact that the signal is not RF.
Early VCRs came with only a coax out and an adapter for antenna
leads. In designing a new format for a better signal from a VCR,
an important criteria was to avoid RF interference. Separating
luma and chroma made it better than composite.

> *Any* kind of baseband video interconnect is an attempt to avoid local
> broadcast RF interference; S-video isn't anything special on that
> specific front.

And I've never said anything to the contrary. If you go back
to the discussion of the user questions and answers from before
you went off-topic in a desperate attempt to prove that you are
correct about irrelevant minutia, the point was that either
s-video or composite were better choices than coax because of
RF interference. He could have used s-video so the topic was
never choosing s-video over composite because of luma and chroma

>>>>As for the subject from last week before the off-topic pissing
>>>It wasn't, actually, a pissing content, until you so declared it.
>>Perhaps you could start a thread explaining why your definition
>>of a pissing contest is superior to all others but substituting
>>"most cities" with "all cities" is an attempt to piss farther.
>>Pissing over Niagara Falls is more of the same ;-).
> I wasn't pissing at all; I was trying to be informative.  If you think
> that one counter example to someone else's rule, which I was merely
> quoting, changes my attempt to be helpful into "pissing", then my
> apologies and condolences.

You've neglected to include your superior definition of a pissing

The question was "In other words, shouldn't mythtv just default
to [using the preset channel] when I'm using an external channel
changing program?" The answer is that devices that output RF have
a switch to select which frequency to use so myth needs an option
to know which preset channel is to be used. Why manufactures
believe that "3" and "4" are adequate choices for most situations
is irrelevant. What is relevant is that devices DO have a selector
switch or software option.

I know for a stone cold fact that there are regulations regarding
where transmission towers can be placed, what frequencies they can
carry and the maximum wattage. I know that atmospheric conditions
affect signal strength at a distance. I know that very few people
watch TV at the base a transmission tower and that most people
live at varying distances from several transmission towers whose
signals they can receive. I know that large expanses of rural
America can get at least a snowy signal on both channel 3 and 4.
I know that the assumption that at least one of these channels
won't have enough interference to be too big of a problem is not
very reassuring. And, I know there are armies of people reading
mailing lists looking some trivial point to try to show off how
smart they are.

With all this in mind, I mentioned that devices have have a
selector switch and the usually choices are 3 and 4 because "most
cities" have one or the other but not both. I deliberately chose
the more flexible "most" knowing that there would be numerous
people chomping at the bit to chime in that they get both where
they live. This does not change the fact that there IS a selector
switch on devices with RF out.

The reason that I was conscious of how I worded it is because I've
read Usenet for decades and have seen this pattern thousands of

1) Someone asks a question.
2) Someone else give a correct answer.
3) Someone else tries to show off how smart they are by nit-picking
a point in the correct answer that adds nothing to answering the
original question.

What I hadn't anticipated is that some know-it-all wannabe would
want to show off that he was 'the one' who knew that there was such
a thing as the FCC to regulate transmissions and replace my cautious
"most cities" with the absolute "all cities". This in no way
changes the fact that there IS a selector switch on devices with RF
out. Instead, it invites other to try to show off that they know
more about whether or not anyone receives adjacent channels. Totally
askew to the topic. Pointless pissing contest.

Any housewife, construction worker or secretary that ever set up a
VCR has seen the switch for 3 or 4, read the quick setup guide and
knew to set it to 4 if they get a strong channel 3 or the other
way around. Anyone who ever saw this could infer that there must
not be any place where there is both a strong 3 and 4. In "trying
to be informative", the only new information  that you contributed
is that you know the web address of Goggle. BTW many housewives,
construction workers and secretaries also know where to find Google.

>>>>The relevant information is that there will be some degree of
>>>>RF interference no matter where you are or which preset channel
>>>>is chosen for output from one of these devices. Therefore, it is
>>>>better to avoid RF altogether by using s-video or composite from
>>>>the device if at all possible. However, if RF coax is used, the
>>>>preset channel needs to be selectable and this is why there has
>>>>to be a configuration option for myth because it cannot assume
>>>>the preset channel for the signal coming from the device will
>>>>always be "3" or will always be "4".
>>>All this is well and goo (and accurate), but was not the original
>>>posters' question: "what do I do about the 'tune card to' option since
>>>my external box sends out video, not RF?"?
>>In your zeal to out piss, you've put words in quotation marks
> Alas, we have no "paraphrase marks" :-)

Your <paraphrase>markings for a paraphrase</paraphrase> included
two completely backwards mis-conceptions. First. the OP was in
fact using RF from his external box and not one of the other video
inputs for his card. Second, he had not originally asked what the
option was for. He had overlooked it entirely and did not know
that this was the option that he needed.

>>which do not appear in Matt Morgan's message of Mon, Aug 2, 2004
>>titled "Quick and dirty workaround":
>>  "How can I keep mythtv from trying to control the channel
>>   internally?"
>>He was concerned about the channel of the tuner on the capture
>>card being changed because he was using the RF tuner input even
>>though it took multiple promptings before he clarified this. He
>>did not ask about the "'tune card to' option" as you suggest. The
>>problem was that he was unaware of the "Preset tuner to channel"
>>option and that this was the solution that he was looking for.
> I guess it was those "multiple promptings" that I missed out on.

That would be consistent with your having not read the thread
and only commenting on the basis of your impressions. In his first
posting he was concerned about keeping the tuner on channel 3
which meant that he must have been using the tuner input. I then
asked him in two messages to verify this just to make sure we
were on the same page. When he confirmed this he said <paraphrase>
he thought it didn't matter</paraphrase> which tells me he was
unaware that the different types of inputs were not equivalent
and the preset channel issue was unique to the tuner input.

>>>Cause that's what *I* thought he was asking about.
>>I have to admire your willingness to at least admit here that
>>you were wrong. Perhaps if you read the actual text rather than
>>making up your own quotes you wouldn't make these mistakes.
> Indeed.  And for that, I apologize.  My snap reaction to his posting,
> as I think was true for others, was "it's supposed to already be doing
> what I think you're saying you want, Matt; what's up?"

> But clearly, I missed the boat a little.
> How nice, that we all have you here, Bruce, to keep us in line.

Not a problem. Glad I could help.

My primary concern is that I want to have the best DVR system
possible. As a result of Matt's misunderstanding of the option
and a related thread a day or two later, I did update the help
text to hopefully help others better understand the preset channel
option in the future.

If you'd like to direct your energies to contribute more to the
project than just trying to show off how smart you are (or show
off how smart you are by contributing code and documentation ;-)
I'm sure those efforts would be appreciated.

--  bjm

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