From: James <bjlockie@lockie.ca>
To: unlisted-recipients:; (no To-header on input)@canuck.infradead.org
Cc: linux-media Mailing List <linux-media@vger.kernel.org>
Subject: Re: femon signal strength
Date: Wed, 26 Oct 2011 15:45:42 -0400 [thread overview]
Message-ID: <4EA86366.1020906@lockie.ca> (raw)
In-Reply-To: <CAGoCfiwS=O75uyaaueNSrq275MS9eednR+Y=yrgsJo0XaExRKA@mail.gmail.com>
On 10/26/11 04:15, Devin Heitmueller wrote:
> On Wed, Oct 26, 2011 at 12:36 AM, James<bjlockie@lockie.ca> wrote:
>> My signal strength is always above 0 but when I use -H, it is 0%.
>> Does that mean my signal strength is<0%?
>> Maybe femon should report 0.x%.
>>
>> $ femon
>> FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC)
>> status SCVYL | signal 00b9 | snr 00b9 | ber 00000000 | unc 00000000 |
>> FE_HAS_LOCK
>>
>> $ femon -H
>> FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC)
>> status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK
>>
>> Is it normal to have<0% signal strength and still get reception?
> For this demodulator, this is normal. The issue is there is no set
> standard for the way in which signal level and SNR are reported in the
> linux DVB API, and as a result there are numerous different formats.
How many different formats are there (do I have to go through the archive)?
Would it be feasable to change femon to handle different formats?
femon was written by Johannes Stezenbach (see DVB-apps/szap/femon.c ).
I'm going to try to change the code to at least work with my FE. :-)
> The format the s5h1409 demodulator driver delivers it doesn't match
> the demodulator that the person who wrote femon had available to
> him/her (the s5h1409 delivers both fields in 0.1dB increments, while
> whatever demod the femon author had to test with expected signal to be
> 0-65535 and SNR to be in 1/256 increments).
>
> In other words if you have an SNR of 30.0 dB, femon sees 0x012c, which
> it treats as a percentage of 0xffff which is 0.00457%, which gets
> rendered as 0%.
>
> Unfortunately, the driver community has never been able to form a
> consensus on how the data should be reported, so you cannot really
> argue the s5h1409 driver is "doing it wrong" (numerous other drivers
> report in the same manner as the s5h1409). You can read the mailing
> list archive for the gory history. It really is a fine example of the
> failure associated with "design by committee".
>
> Devin
>
next prev parent reply other threads:[~2011-10-26 19:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-26 4:36 femon signal strength James
2011-10-26 8:15 ` Devin Heitmueller
2011-10-26 19:45 ` James [this message]
2011-10-26 19:49 ` Devin Heitmueller
2011-10-26 19:58 ` James
2011-11-05 10:10 ` Steffen Barszus
[not found] ` <CAGoCfiwC+7pkY6ZchySBYRkyY1XjFjKeJYQEPTc2ZiBN-pdoyw@mail.gmail.com>
2011-11-06 13:15 ` Steffen Barszus
[not found] ` <CAGoCfixoOwZumohwJrLVKhfpUNGYwbD9uSq7nM0GhqriOx0FxA@mail.gmail.com>
2011-11-06 19:59 ` Steffen Barszus
2011-11-07 10:47 ` Andreas Oberritter
2011-11-07 15:13 ` Luca Olivetti
2011-11-07 19:16 ` Andreas Oberritter
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