Instead of just estimating the bandwidth for DVB-C annex A/C,
also fill it at the core for ATSC and DVB-C annex B. This
simplifies the logic inside the tuners, as all non-satellite
tuners can just use c->bandwidth_hz for all supported
delivery systems.
It could make sense to latter use it also for satellite
systems, as several DVB-S drivers have their own calculus.
However, on DVB-S2 the bw estimation is a little more complex,
and the existing drivers have some optimized calculus for
bandwidth. So, let's not touch on it for now.
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
---
drivers/media/dvb/dvb-core/dvb_frontend.c | 35 ++++++++++++++++++++++------
1 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c
index a25ba3a..8dedff4 100644
--- a/drivers/media/dvb/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb/dvb-core/dvb_frontend.c
@@ -1180,19 +1180,38 @@ static void dtv_property_adv_params_sync(struct dvb_frontend *fe)
}
/*
- * On DVB-C, the bandwidth is a function of roll-off and symbol rate.
- * The bandwidth is required for DVB-C tuners, in order to avoid
- * inter-channel noise. Instead of estimating the minimal required
- * bandwidth on every single driver, calculates it here and fills
- * it at the cache bandwidth parameter.
+ * Be sure that the bandwidth will be filled for all
+ * non-satellite systems, as tuners need to know what
+ * low pass/Nyquist half filter should be applied, in
+ * order to avoid inter-channel noise.
+ *
+ * ISDB-T and DVB-T/T2 already sets bandwidth.
+ * ATSC and DVB-C don't set, so, the core should fill it.
+ *
+ * On DVB-C Annex A and C, the bandwidth is a function of
+ * the roll-off and symbol rate. Annex B defines different
+ * roll-off factors depending on the modulation. Fortunately,
+ * Annex B is only used with 6MHz, so there's no need to
+ * calculate it.
+ *
* While not officially supported, a side effect of handling it at
* the cache level is that a program could retrieve the bandwidth
- * via DTV_BANDWIDTH_HZ, wich may be useful for test programs.
+ * via DTV_BANDWIDTH_HZ, which may be useful for test programs.
*/
- if (c->delivery_system == SYS_DVBC_ANNEX_A)
+ switch (c->delivery_system) {
+ case SYS_ATSC:
+ case SYS_DVBC_ANNEX_B:
+ c->bandwidth_hz = 6000000;
+ break;
+ case SYS_DVBC_ANNEX_A:
rolloff = 115;
- if (c->delivery_system == SYS_DVBC_ANNEX_C)
+ break;
+ case SYS_DVBC_ANNEX_C:
rolloff = 113;
+ break;
+ default:
+ break;
+ }
if (rolloff)
c->bandwidth_hz = (c->symbol_rate * rolloff) / 100;
}
--
1.7.8.352.g876a6
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