On Monday 7 January 2013 22:25:47 Mauro Carvalho Chehab wrote: <snip> > + <itemizedlist mark='bullet'> > + > <listitem><para><constant>FE_SCALE_NOT_AVAILABLE</constant> - If it is not > possible to collect a given parameter (could be a transitory or permanent > condition)</para></listitem> > + > <listitem><para><constant>FE_SCALE_DECIBEL</constant> - parameter is a signed > value, measured in 0.1 dB</para></listitem> > + > <listitem><para><constant>FE_SCALE_RELATIVE</constant> - parameter is a > unsigned value, where 0 means 0% and 65535 means 100%.</para></listitem> > + > <listitem><para><constant>FE_SCALE_COUNTER</constant> - parameter is a > unsigned value that counts the occurrence of an event, like bit error, block > error, or lapsed time.</para></listitem> > + </itemizedlist> <snip> > + <section id="DTV-QOS-SIGNAL-STRENGTH"> > + <title><constant>DTV_QOS_SIGNAL_STRENGTH</constant></title> > + <para>Indicates the signal strength level at the analog part of > the tuner.</para> > + </section>
Signal strength is traditionally an absolute field strength; there's no way in this API for me to provide my reference point, so two different front ends could represent the same signal strength as "0 dB" (where the reference point is one microwatt), "-30 dB" (where the reference point is one milliwatt), or "17 dB" (using a reference point of 1 millivolt on a 50 ohm impedance). Could you choose a reference point for signal strength, and specify that if you're using FE_SCALE_DECIBEL, you're referenced against that point? My preference would be to reference against 1 microwatt, as (on the DVB-T and ATSC cards I use) that leads to the signal measure being 0 dBµW if you've got perfect signal, negative number if your signal is weak, and positive numbers if your signal is strong. However, referenced against 1 milliwatt also works well for me, as the conversion is trivial. -- Simon Farnsworth Software Engineer ONELAN Ltd http://www.onelan.com -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
