From: Steven Toth <stoth@kernellabs.com>
To: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Cc: Linux Media Mailing List <linux-media@vger.kernel.org>,
Mauro Carvalho Chehab <mchehab@infradead.org>,
Jonathan Corbet <corbet@lwn.net>,
Michael Ira Krufky <mkrufky@linuxtv.org>
Subject: Re: [PATCH 08/10] dvb_frontend: create a new ops to help returning signals in dB
Date: Thu, 30 Jun 2016 09:48:30 -0400 [thread overview]
Message-ID: <CALzAhNUdS_aQ+gTHAJ02whAuUcOOpTpJUo33NK7FWYx_EmgSjQ@mail.gmail.com> (raw)
In-Reply-To: <790b5e1664c84e806a13143eff1c79b95fb4bf63.1467240152.git.mchehab@s-opensource.com>
> add a new ops that will allow tuners to better report the
> dB level of its AGC logic to the demod drivers. As the maximum
> gain may vary from tuner to tuner, we'll be reversing the
> logic here: instead of reporting the gain, let's report the
> attenuation. This way, converting from it to the legacy DVBv3
> way is trivial. It is also easy to adjust the level of
> the received signal to dBm, as it is just a matter of adding
> an offset at the demod and/or at the bridge driver.
Mauro,
Have you verified this work with a detailed spectrum analysis study?
If so then please share. For example, by measuring the I/F out of
various tuners in a mix of use cases, with and without the AGC being
driven by any downstream demodulator? Also, taking into consideration
any external LNA variance.
I'm concerned that a tuner AGC Gain is a meaningless measurement and
in practice demodulators don't actually care, and tuners don't
implement their gain reporting capabilities correctly at all.
This feels like a solution to a problem that doesn't exist.
--
Steven Toth - Kernel Labs
http://www.kernellabs.com
+1.646.355.8490
next prev parent reply other threads:[~2016-06-30 13:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-29 22:43 [PATCH 01/10] xc5000: add support to return RF strength Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 02/10] au8522: use the RF strentgh provided by the tuner Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 03/10] au8522: add support for dvbv5 statistics API Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 04/10] au8522: reorder functions to avoid a forward declaration Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 05/10] au8522: remove au8522_read_ber() ops Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 06/10] au8522: show signal strength in dBm, for devices with xc5000 Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 07/10] lgdt3306a: Expose SNR via dvbv5 stats Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 08/10] dvb_frontend: create a new ops to help returning signals in dB Mauro Carvalho Chehab
2016-06-30 13:48 ` Steven Toth [this message]
2016-06-30 15:01 ` Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 09/10] au8522/xc5000: use the new get_rf_attenuation() ops Mauro Carvalho Chehab
2016-06-29 22:43 ` [PATCH 10/10] lgdt3306a: better handle RF fake strength Mauro Carvalho Chehab
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