[linux-dvb] [RFC] [PATCH] Make S/N values to appear at cx24123 frontend

Mauro Carvalho Chehab mchehab at infradead.org
Fri Apr 14 19:15:42 CEST 2006


I think this is the final version of this patch, based on what we have

I've decided to use u64, instead of all those shifts. This way, we can
improve the precision for lower BER rates. Here, it worked like a charm:

cx24123: cx24123_read_ber:  BER = 6380
cx24123: cx24123_read_snr:  read S/N index = 63948

Em Sex, 2006-04-14 às 07:09 -0300, Mauro Carvalho Chehab escreveu:
> Em Sex, 2006-04-14 às 01:33 -0700, Trent Piepho escreveu:
> > So anyway, here is my version of linear interpolation.  It has a simpler
> > formula in the code, and much better rounding behavior, as you can see in the
> > plot here:  http://www.speakeasy.org/~xyzzy/ber-snr.png
> Sounds good. I'll replace the corresponding parts at my code. May I
> include your Signed-off-by at the patch?


This patch fixes SNR detection on cx24123

From: Mauro Carvalho Chehab

Current code is broken, since, before calling SNR, BER code should be
called. After the patch, cx24123 will:
1) Show SNR only if signal is locked;
2) SNR estimation based on BER rate;
3) The estimation uses linear interpolation on segmented intervals to
improve performance

Signed-off-by: Mauro Carvalho Chehab

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