Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0607d077 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[media] dvb_core: estimate bw for all non-terrestial systems 



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: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 0349471b

drivers/media/dvb/dvb-core/dvb_frontend.c

+27 −8
Original line number Diff line number Diff line
@@ -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;

}