Mailing List Archive: HVR-1600 femon shows no signal strength

HVR-1600 femon shows no signal strength

Aug 21, 2011, 8:54 PM

Post #1 of 6 (3464 views)

Hi,

I'm trying to point my antenna to get better ATSC reception with my
HVR-1600. I'm using "femon" from the dvbtools package on ubuntu 10.10
without any luck.

Here's a sample of the femon output (regular format):
nikosapi@mythbackend:~$ femon -c 3
FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC)
status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
FE_HAS_LOCK
status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
FE_HAS_LOCK
status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

And here's the human readable output:
nikosapi@mythbackend:~$ femon -c 3 -H
FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC)
status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK
status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK
status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK

This is on a channel that has almost perfect signal strength on my TV.
I'm using "zap" to select the channel like so:
nikosapi@mythbackend:~$ zap -channels channels-11-08-21.conf CKMI-HD
Using frontend "Samsung S5H1409 QAM/8VSB Frontend", type ATSC
Problem retrieving frontend information: Invalid argument
status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

Any ideas?

Thanks,

nick

_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users

Re: HVR-1600 femon shows no signal strength [ In reply to ]

awalls at md

Aug 24, 2011, 3:37 AM

Post #2 of 6 (3399 views)

Permalink

On Sun, 2011-08-21 at 23:54 -0400, Nick Nobody wrote:
> Hi,
>
> I'm trying to point my antenna to get better ATSC reception with my
> HVR-1600. I'm using "femon" from the dvbtools package on ubuntu 10.10
> without any luck.
>
> Here's a sample of the femon output (regular format):
> nikosapi@mythbackend:~$ femon -c 3
> FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC)
> status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
> FE_HAS_LOCK
> status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
> FE_HAS_LOCK
> status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
> FE_HAS_LOCK
>
> And here's the human readable output:
> nikosapi@mythbackend:~$ femon -c 3 -H
> FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC)
> status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK
> status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK
> status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK
>
> This is on a channel that has almost perfect signal strength on my TV.
> I'm using "zap" to select the channel like so:
> nikosapi@mythbackend:~$ zap -channels channels-11-08-21.conf CKMI-HD
> Using frontend "Samsung S5H1409 QAM/8VSB Frontend", type ATSC
> Problem retrieving frontend information: Invalid argument
> status SCVYL | signal 012c | snr 012c | ber 00000000 | unc 00000000 |
> FE_HAS_LOCK
>
> Any ideas?

What's wrong aside from the human readable output mode of femon being
broken? Do you have a picture or not?

You have a lock.
You have a pretty high SNR value (my ATSC reception always has a value
of less than 0x100).
You have 0 block errors and uncorrectable errors.

Regards,
Andy

> Thanks,
>
> nick

_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users

Re: HVR-1600 femon shows no signal strength [ In reply to ]

dheitmueller at kernellabs

Aug 24, 2011, 5:24 AM

Post #3 of 6 (3393 views)

Permalink

On Wed, Aug 24, 2011 at 6:37 AM, Andy Walls <awalls@md.metrocast.net> wrote:
> What's wrong aside from the human readable output mode of femon being
> broken? Do you have a picture or not?
>
> You have a lock.
> You have a pretty high SNR value (my ATSC reception always has a value
> of less than 0x100).
> You have 0 block errors and uncorrectable errors.
>
> Regards,
> Andy

Andy,

My guess is that this is actually the s5h1409 being dumb in a couple of ways:

It puts the same SNR value into both the strength and signal fields.

Most demods treat the signal field as a scaled value from 0-65535
where 65535=100%. So femon probably treats 0x012c as 300/65535 which
as a percentage is rounded to "0%".

So while part of this is femon making some assumptions about how the
values are rendered, much of the problem continues to be the lack of
uniformity for the strength/snr fields in the DVB interface, and the
s5h1409 just happens to do it in an unpopular way.

Nick: Just use the non-human readable values. This problem isn't
going to be fixed anytime in the near future given the inability of
the LinuxTV community to agree on a format for providing SNR/signal
info across all demod drivers (I've been pushing for that for *years*
now).

Devin

--
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users

Re: HVR-1600 femon shows no signal strength [ In reply to ]

me at nikosapi

Aug 24, 2011, 6:25 AM

Post #4 of 6 (3390 views)

Permalink

On Wed, 2011-08-24 at 08:24 -0400, Devin Heitmueller wrote:
> On Wed, Aug 24, 2011 at 6:37 AM, Andy Walls <awalls@md.metrocast.net> wrote:
> > What's wrong aside from the human readable output mode of femon being
> > broken? Do you have a picture or not?
> >
> > You have a lock.
> > You have a pretty high SNR value (my ATSC reception always has a value
> > of less than 0x100).
> > You have 0 block errors and uncorrectable errors.
> >
> > Regards,
> > Andy
>
> Andy,
>
> My guess is that this is actually the s5h1409 being dumb in a couple of ways:
>
> It puts the same SNR value into both the strength and signal fields.
>
> Most demods treat the signal field as a scaled value from 0-65535
> where 65535=100%. So femon probably treats 0x012c as 300/65535 which
> as a percentage is rounded to "0%".
>
> So while part of this is femon making some assumptions about how the
> values are rendered, much of the problem continues to be the lack of
> uniformity for the strength/snr fields in the DVB interface, and the
> s5h1409 just happens to do it in an unpopular way.
>
> Nick: Just use the non-human readable values. This problem isn't
> going to be fixed anytime in the near future given the inability of
> the LinuxTV community to agree on a format for providing SNR/signal
> info across all demod drivers (I've been pushing for that for *years*
> now).
>
> Devin
>

Thanks Andy and Devin for your responses :)

It seems both femon and I assumed the upper bound for the signal quality
and snr was 0xffff. That makes sense that femon would not accurately
report those values in the "human readable" format.

Do either of you know off hand what the upper limit is for those values?
If not don't waste your time, I'll dig around for them.

Devin: In the past I'm pretty sure I've seen the signal strength and snr
values differ (albeit not by much) but for the most part they're exactly
the same.

For example:

status SCVYL | signal 00f0 | snr 00f0 | ... | FE_HAS_LOCK
status SCVYL | signal 00f5 | snr 00f0 | ... | FE_HAS_LOCK
status SCVYL | signal 00f0 | snr 00f5 | ... | FE_HAS_LOCK
status SCVYL | signal 00f5 | snr 00f0 | ... | FE_HAS_LOCK
status SCVYL | signal 00f0 | snr 00f0 | ... | FE_HAS_LOCK

Anyway, thanks for your help guys!

nick

_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users

Re: HVR-1600 femon shows no signal strength [ In reply to ]

dheitmueller at kernellabs

Aug 24, 2011, 6:31 AM

Post #5 of 6 (3386 views)

Permalink

On Wed, Aug 24, 2011 at 9:25 AM, Nick Nobody <me@nikosapi.org> wrote:
> Thanks Andy and Devin for your responses :)
>
> It seems both femon and I assumed the upper bound for the signal quality
> and snr was 0xffff. That makes sense that femon would not accurately
> report those values in the "human readable" format.
>
> Do either of you know off hand what the upper limit is for those values?
> If not don't waste your time, I'll dig around for them.

For ATSC, the upper bound for SNR is 30.0 dB. The value is in hex on
a 0.1dB scale, so 0x12c = 300 = 30.0 dB. For ClearQAM the upper bound
is 40.0.

> Devin: In the past I'm pretty sure I've seen the signal strength and snr
> values differ (albeit not by much) but for the most part they're exactly
> the same.

There might be some slight variance because the two values are not
retrieved in the kernel call. So basically you're seeing the same
value sampled twice, so you might see slight deviation even though the
two values are printed on the same line.

Devin

--
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users

Re: HVR-1600 femon shows no signal strength [ In reply to ]

me at nikosapi

Aug 24, 2011, 9:03 AM

Post #6 of 6 (3387 views)

Permalink

On Wed, 2011-08-24 at 09:31 -0400, Devin Heitmueller wrote:
> On Wed, Aug 24, 2011 at 9:25 AM, Nick Nobody <me@nikosapi.org> wrote:
> > Thanks Andy and Devin for your responses :)
> >
> > It seems both femon and I assumed the upper bound for the signal quality
> > and snr was 0xffff. That makes sense that femon would not accurately
> > report those values in the "human readable" format.
> >
> > Do either of you know off hand what the upper limit is for those values?
> > If not don't waste your time, I'll dig around for them.
>
> For ATSC, the upper bound for SNR is 30.0 dB. The value is in hex on
> a 0.1dB scale, so 0x12c = 300 = 30.0 dB. For ClearQAM the upper bound
> is 40.0.
>
> > Devin: In the past I'm pretty sure I've seen the signal strength and snr
> > values differ (albeit not by much) but for the most part they're exactly
> > the same.
>
> There might be some slight variance because the two values are not
> retrieved in the kernel call. So basically you're seeing the same
> value sampled twice, so you might see slight deviation even though the
> two values are printed on the same line.
>
> Devin
>

Cool, thanks for the info Devin.

nick

_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users