[linux-dvb] [RFC] SNR units in tuners

Matthias Schwarzott zzam at gentoo.org
Sat Oct 18 21:38:02 CEST 2008

On Freitag, 17. Oktober 2008, Devin Heitmueller wrote:
> Hello,
> In response to Steven Toth's suggestion regarding figuring out what
> the various units are across demodulators, I took a quick inventory
> and came up with the following list.  Note that this is just a first
> pass by taking a quick look at the source for each demodulator (I
> haven't looked for the datasheets for any of them yet or done sample
> captures to see what the reported ranges are).
> Could everybody who is responsible for a demod please take a look at
> the list and see if you can fill in the holes?
> Having a definitive list of the current state is important to being
> able to provide unified reporting of SNR.
> Thank you,
> Devin

> mt312.c         unknown

The hardware provides two values:
* AGC: For now the AGC feedback value (14 bit) is returned unchanged.
* ERR_db: Also available is a 10-bit value representing the signal level 
difference between AGC-Reference and received signal level (most likely in 
1dB steps).

If an absolute value is needed: I don't get it how to calc absolute signal 
levels from AGC-Reference.

so code for now:
mt312.c: agc-feedback 0-0x3FFF

Any additions?


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