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media: vidtv: adjust signal strength range

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On real devices, signal strength is always a negative
number when represented in dBm. A more interesting
range is to use dBmV (which is what Kaffeine does,
for example). The conversion from the two units are
simple:

	dBmV = dBm - 108

Usually, signal strength ranges up to 100dBmV. Adjust the
maximum value to be around 74 dBmV, when there's no
frequency shift, which represents a good signal.

With that, Kaffeine displays it a lot better.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Mauro Carvalho Chehab 2020-09-14 15:17:18 +02:00
parent 9cf8572d6b
commit d859a712a3
1 changed files with 9 additions and 3 deletions
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12
drivers/media/test-drivers/vidtv/vidtv_demod.c
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@ -181,12 +181,18 @@ static void vidtv_demod_update_stats(struct dvb_frontend *fe)
c->block_count.stat[0].scale = scale;
/*
* Add a 0.5% of randomness at the signal streangth and CNR,
* Add a 0.5% of randomness at the signal strength and CNR,
* and make them different, as we want to have something closer
* to a real case scenario.
*
* Also, usually, signal strength is a negative number in dBm.
*/
c->strength.stat[0].svalue = state->tuner_cnr + prandom_u32_max(state->tuner_cnr / 50);
c->cnr.stat[0].svalue = state->tuner_cnr - prandom_u32_max(state->tuner_cnr / 50);
c->strength.stat[0].svalue = state->tuner_cnr;
c->strength.stat[0].svalue -= prandom_u32_max(state->tuner_cnr / 50);
c->strength.stat[0].svalue -= 68000; /* Adjust to a better range */
c->cnr.stat[0].svalue = state->tuner_cnr;
c->cnr.stat[0].svalue -= prandom_u32_max(state->tuner_cnr / 50);
}