Mailing List Archive

OSD Signal Strength
Does anyone know how or what the OSD signal % means?

I am using the current release of Mythbuntu (7.10) with a Leadtek DTV2000H card receiving Free to Air DVB-T ( all VHF freq ) in Sydney, Australia

Last night I was playing around with the antenna system which has a masthead amp and got the following readings

1) Lead direct to wall ***Signal 50% - S/N 4.8 db - BE 0 - Lock OK
2) 10db attenuation ***Signal 55% - S/N 4.8db - BE 0 Lock OK
3) 20bd attenuation *** Signal 60% - S/N 4.8db - BE 0 Lock OK
4) 2 way splitter *** Signal 75% - S/N 4.8db - BE 0 Lock OK
5) 3 way splitter *** Signal 100% - S/N 4.8db - BE 0 No Lock
6) 4 way splitter/Amp +12db *** Signal 35% - S/N 4.8db - BE 0 Lock OK
7) 2 piggy backed splitter/amps ***Signal 20% - S/N 4.8db - BE 1000 No Lock

From this I am getting the idea that the % is inverse to the actual signal strength and that below 20% I am actually overloading the card.

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Re: OSD Signal Strength [ In reply to ]
Quoting noelcollins@optusnet.com.au:

> Does anyone know how or what the OSD signal % means?
>
> I am using the current release of Mythbuntu (7.10) with a Leadtek
> DTV2000H card receiving Free to Air DVB-T ( all VHF freq ) in
> Sydney, Australia
>
> Last night I was playing around with the antenna system which has a
> masthead amp and got the following readings
>
> 1) Lead direct to wall ***Signal 50% - S/N 4.8 db - BE 0 - Lock OK
> 2) 10db attenuation ***Signal 55% - S/N 4.8db - BE 0 Lock OK
> 3) 20bd attenuation *** Signal 60% - S/N 4.8db - BE 0 Lock OK
> 4) 2 way splitter *** Signal 75% - S/N 4.8db - BE 0 Lock OK
> 5) 3 way splitter *** Signal 100% - S/N 4.8db - BE 0 No Lock
> 6) 4 way splitter/Amp +12db *** Signal 35% - S/N 4.8db - BE 0 Lock OK
> 7) 2 piggy backed splitter/amps ***Signal 20% - S/N 4.8db - BE 1000 No Lock
>
> From this I am getting the idea that the % is inverse to the actual
> signal strength and that below 20% I am actually overloading the card.

Disclaimer: I'm a QAM/DVB-C guy, I don't know much about DVB-T.

The numbers come from from the Video4Linux driver, and there are some
drivers that are known to give incorrect numbers (the driver for the
DViCO Fusion Lite back when I used it). A 4.8DB Signal-to-Noise ratio
is horrendous, and would not actually give a usable signal (at least
not in a DVB-C/QAM world).

It's been over a year since I've done any V4L work (not driver
development, just a simple QAM capture program), and I found that the
API for fetching the signal level at that time *suggested* a return
value from 0-65535 for signal strength (0 being 0%, 65535 being 100%),
but not all drivers necessarily honor that.

I would say that direct to the wall is probably your best signal, 20DB
is some serious attenuation. However, you may very well have to do
things by trial and error.

If you really need to know the signal levels, then you'll either need
a different DVB-T card (where the numbers are implemented correctly),
or use another OS/piece of hardware that gets it right.

-- Joe


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Re: OSD Signal Strength [ In reply to ]
I know the s/n value was strange but it was only when I had HIGH% signal that I was getting pixelation and sound "pops". I'm about 40-50kms from the transmitters and have always had a "noisy" analog signal.
I would love to see what the true signal strength is but I dont have access to any antenna test gear.
I mainly tried the experiment so I could work out an antenna distribution design for my network which will have a rack of 1 master and 6 or 7 secondary backends coupled to 3 or 4 remote frontends. With three boys, 19,10,8, the wife and myself we record/timeshift a hell of a lot.


> Joe Votour <vulturej@vulturesnest.net> wrote:
>
> Quoting noelcollins@optusnet.com.au:
>
> > Does anyone know how or what the OSD signal % means?
> >
> > I am using the current release of Mythbuntu (7.10) with a Leadtek
> > DTV2000H card receiving Free to Air DVB-T ( all VHF freq ) in
> > Sydney, Australia
> >
> > Last night I was playing around with the antenna system which has a
> > masthead amp and got the following readings
> >
> > 1) Lead direct to wall ***Signal 50% - S/N 4.8 db - BE 0 - Lock OK
> > 2) 10db attenuation ***Signal 55% - S/N 4.8db - BE 0 Lock OK
> > 3) 20bd attenuation *** Signal 60% - S/N 4.8db - BE 0 Lock OK
> > 4) 2 way splitter *** Signal 75% - S/N 4.8db - BE 0 Lock OK
> > 5) 3 way splitter *** Signal 100% - S/N 4.8db - BE 0 No Lock
> > 6) 4 way splitter/Amp +12db *** Signal 35% - S/N 4.8db - BE 0 Lock OK
> > 7) 2 piggy backed splitter/amps ***Signal 20% - S/N 4.8db - BE 1000 No
> Lock
> >
> > From this I am getting the idea that the % is inverse to the actual
> > signal strength and that below 20% I am actually overloading the card.
>
> Disclaimer: I'm a QAM/DVB-C guy, I don't know much about DVB-T.
>
> The numbers come from from the Video4Linux driver, and there are some
> drivers that are known to give incorrect numbers (the driver for the
> DViCO Fusion Lite back when I used it). A 4.8DB Signal-to-Noise ratio
> is horrendous, and would not actually give a usable signal (at least
> not in a DVB-C/QAM world).
>
> It's been over a year since I've done any V4L work (not driver
> development, just a simple QAM capture program), and I found that the
> API for fetching the signal level at that time *suggested* a return
> value from 0-65535 for signal strength (0 being 0%, 65535 being 100%),
> but not all drivers necessarily honor that.
>
> I would say that direct to the wall is probably your best signal, 20DB
> is some serious attenuation. However, you may very well have to do
> things by trial and error.
>
> If you really need to know the signal levels, then you'll either need
> a different DVB-T card (where the numbers are implemented correctly),
> or use another OS/piece of hardware that gets it right.
>
> -- Joe
>
>
> __________________________________________________
> D O T E A S Y - "Join the web hosting revolution!"
> http://www.doteasy.com
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Re: OSD Signal Strength [ In reply to ]
On Wed, Mar 5, 2008 at 12:16 PM, <noelcollins@optusnet.com.au> wrote:
> which will have a rack of 1 master and 6 or 7 secondary backends coupled to 3 or 4 remote frontends. With three boys, 19,10,8, the wife
> and myself we record/timeshift a hell of a lot.
>
>


There are 5/6 in my family and I have a single BE and 3 (not enough)
FE's but I manage to record most things. Once 0.21 (and therefore
multi-record) comes along, I don't think I will ever need to dodge any
conflicting shows. (I am in Brisbane).

How many channels you planning on recording at any one time?
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Re: OSD Signal Strength [ In reply to ]
Probable 5 or more. At present we have 3 VCRs that on some nights are all recording (analog) with 1 or 2 mythboxes recording from digital. Designed the setup because of the problem of back to back schedule recording, especially when the commercial stations are "loose" with their start/end times.
The pc's are ex work P4 2.4Ghz - just add tuner $89 / 250-500Gb HDD $100-$120 = 1 backend. Need to keep frontends from recording stream as much as possible so we use frontends to watch live digital tv.



> David Whyte <david.whyte@gmail.com> wrote:
>
> On Wed, Mar 5, 2008 at 12:16 PM, <noelcollins@optusnet.com.au> wrote:
> > which will have a rack of 1 master and 6 or 7 secondary backends
> coupled to 3 or 4 remote frontends. With three boys, 19,10,8, the wife
> > and myself we record/timeshift a hell of a lot.
> >
> >
>
>
> There are 5/6 in my family and I have a single BE and 3 (not enough)
> FE's but I manage to record most things. Once 0.21 (and therefore
> multi-record) comes along, I don't think I will ever need to dodge any
> conflicting shows. (I am in Brisbane).
>
> How many channels you planning on recording at any one time?
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Re: OSD Signal Strength [ In reply to ]
noelcollins@optusnet.com.au wrote:
> Probable 5 or more. At present we have 3 VCRs that on some nights are all recording (analog) with 1 or 2 mythboxes recording from digital. Designed the setup because of the problem of back to back schedule recording, especially when the commercial stations are "loose" with their start/end times.
> The pc's are ex work P4 2.4Ghz - just add tuner $89 / 250-500Gb HDD $100-$120 = 1 backend. Need to keep frontends from recording stream as much as possible so we use frontends to watch live digital tv.

You really don't need that much in Australia, where we only have like 5
or 6 channels. With multi-rec in 0.21, you can overlap back-to-back
shows and record the SD and HD channels simultaneously on one tuner (so
you can record shows back-to-back with overlap on both Seven and SevenHD
with one tuner only).

1 BE with maybe two dual-tuners would be more than enough for all of that.

Anyway, this is starting to go off-topic of your original post, which I
personally can't comment on, not being familiar with all that stuff...
I'm lucky enough to live on top of a hill with excellent receptions for
all channels :-)

Dean.

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Re: OSD Signal Strength [ In reply to ]
On Wed, Mar 5, 2008 at 1:29 PM, <noelcollins@optusnet.com.au> wrote:
> Designed the setup because of the problem of back to back schedule recording, especially when the commercial stations are "loose" with their start/end times.

Okie dokie. Multi-rec should alleviate the problem with back to back
recordings though, just so you are aware. One tuner can be used to
record where the two shows overlap to two separate recording files.

HTH's
Whytey
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Re: OSD Signal Strength [ In reply to ]
I'm having some pixelation in my MythTV recordings , how can I debug or show
signal strengh easily.

It would be useful to have a signal strengh output in the mythbackend.log
during the start/end of recording so I can see if its an ongoing issue. I'm
only getting this for one channel at present (ABC / Canberra).

Any one any advise how to display this automatically .

thanks

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Re: OSD Signal Strength [ In reply to ]
On Sun, Mar 16, 2008 at 5:32 PM, mtrax11 <mylists@wilsononline.id.au> wrote:
>
> I'm having some pixelation in my MythTV recordings , how can I debug or show
> signal strengh easily.
>
> It would be useful to have a signal strengh output in the mythbackend.log
> during the start/end of recording so I can see if its an ongoing issue. I'm
> only getting this for one channel at present (ABC / Canberra).
>
> Any one any advise how to display this automatically .
>

If you can get it I suspect it's a device driver issue and not
somethign you can get from within MythTV itself. I would suggest
looking at options for your device driver.

If you find a solution and can report back please do. I've not had
this problem much with ivtv and my PVR-150's but I think it would be
interesting to look at.

thanks,
Mark
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Re: OSD Signal Strength [ In reply to ]
I'm not sure if its a device driver as most other channels are fine
I'm using a DVB-T AirStar and DNTV Live pro



Mark Knecht wrote:
>
> On Sun, Mar 16, 2008 at 5:32 PM, mtrax11 <mylists@wilsononline.id.au>
> wrote:
>>
>> I'm having some pixelation in my MythTV recordings , how can I debug or
>> show
>> signal strengh easily.
>>
>> It would be useful to have a signal strengh output in the
>> mythbackend.log
>> during the start/end of recording so I can see if its an ongoing issue.
>> I'm
>> only getting this for one channel at present (ABC / Canberra).
>>
>> Any one any advise how to display this automatically .
>>
>
> If you can get it I suspect it's a device driver issue and not
> somethign you can get from within MythTV itself. I would suggest
> looking at options for your device driver.
>
> If you find a solution and can report back please do. I've not had
> this problem much with ivtv and my PVR-150's but I think it would be
> interesting to look at.
>
> thanks,
> Mark
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>

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Re: OSD Signal Strength [ In reply to ]
Quoting mtrax11 <mylists@wilsononline.id.au>:

>
> I'm not sure if its a device driver as most other channels are fine
> I'm using a DVB-T AirStar and DNTV Live pro
>
<snip>

Since you're using a DVB-T card, you may be better off using dvbtools
rather than trying to fit constant signal monitoring into MythTV.
MythTV gets the same information as the tools do, as they both come
from the same driver level controls.

The other thing with using dvbtools is that you'll also be able to
determine whether or not it really is a signal issue, or an issue with
some other part of the system.

-- Joe


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Re: OSD Signal Strength [ In reply to ]
mtrax11 wrote:
> I'm having some pixelation in my MythTV recordings , how can I debug or show
> signal strengh easily.
>
> It would be useful to have a signal strengh output in the mythbackend.log
> during the start/end of recording so I can see if its an ongoing issue. I'm
> only getting this for one channel at present (ABC / Canberra).
>
> Any one any advise how to display this automatically .
>
> thanks
>

I just hit F7 and flip through all my channels as I adjust the antenna.
I set it in the optimal position for all channels. It may not be highest
signal for one or two, but gets a nonpixelating signal on all of them.
Myth won't record while checking signal strength.

Raphael
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Re: OSD Signal Strength [ In reply to ]
What does F7 do? is that another key for changing channels? ie doesn't
up/down change channel?

thanks


Raphael Pooser wrote:
>
> mtrax11 wrote:
>> I'm having some pixelation in my MythTV recordings , how can I debug or
>> show
>> signal strengh easily.
>>
>> It would be useful to have a signal strengh output in the mythbackend.log
>> during the start/end of recording so I can see if its an ongoing issue.
>> I'm
>> only getting this for one channel at present (ABC / Canberra).
>>
>> Any one any advise how to display this automatically .
>>
>> thanks
>>
>
> I just hit F7 and flip through all my channels as I adjust the antenna.
> I set it in the optimal position for all channels. It may not be highest
> signal for one or two, but gets a nonpixelating signal on all of them.
> Myth won't record while checking signal strength.
>
> Raphael
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>

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Re: OSD Signal Strength [ In reply to ]
<fixed top posting>

On 03/17/2008 04:05 PM, mtrax11 wrote:
> Raphael Pooser wrote:
>
>> mtrax11 wrote:
>>
>>> I'm having some pixelation in my MythTV recordings , how can I debug or
>>> show
>>> signal strengh easily.
>>>
>>> It would be useful to have a signal strengh output in the mythbackend.log
>>> during the start/end of recording so I can see if its an ongoing issue.
>>> I'm
>>> only getting this for one channel at present (ABC / Canberra).
>>>
>>> Any one any advise how to display this automatically .
>> I just hit F7 and flip through all my channels as I adjust the antenna.
>> I set it in the optimal position for all channels. It may not be highest
>> signal for one or two, but gets a nonpixelating signal on all of them.
>> Myth won't record while checking signal strength.
> What does F7 do? is that another key for changing channels? ie doesn't
> up/down change channel?

F7 is the key that /used/ to be bound to the SIGNALMON action (brings up
the signal monitor) in the TV Playback context. That key has been
replaced with the Alt-F7 key sequence in 0.21 and beyond for those users
who have not modified the default value (i.e. if you had ever changed
SIGNALMON from F7--i.e. with MythControls--your custom key continues to
work).

Mike
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Re: OSD Signal Strength [ In reply to ]
Michael T. Dean wrote:
> <fixed top posting>
>
> On 03/17/2008 04:05 PM, mtrax11 wrote:
>> Raphael Pooser wrote:
>>
>>> mtrax11 wrote:
>>>
>>>> I'm having some pixelation in my MythTV recordings , how can I debug or
>>>> show
>>>> signal strengh easily.
>>>>
>>>> It would be useful to have a signal strengh output in the mythbackend.log
>>>> during the start/end of recording so I can see if its an ongoing issue.
>>>> I'm
>>>> only getting this for one channel at present (ABC / Canberra).
>>>>
>>>> Any one any advise how to display this automatically .
>>> I just hit F7 and flip through all my channels as I adjust the antenna.
>>> I set it in the optimal position for all channels. It may not be highest
>>> signal for one or two, but gets a nonpixelating signal on all of them.
>>> Myth won't record while checking signal strength.
>> What does F7 do? is that another key for changing channels? ie doesn't
>> up/down change channel?
>
> F7 is the key that /used/ to be bound to the SIGNALMON action (brings up
> the signal monitor) in the TV Playback context. That key has been
> replaced with the Alt-F7 key sequence in 0.21 and beyond for those users
> who have not modified the default value (i.e. if you had ever changed
> SIGNALMON from F7--i.e. with MythControls--your custom key continues to
> work).
>
> Mike
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>

Yes, I'm not using 0.21, should have mentioned.... Using some svn from
not too long before the release, so figured most things would be the
same. Hopefully this is what you meant when you were asking about easy
way to show signal strength.
cheers
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