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  1. 21 9月, 2011 2 次提交
  3. 07 9月, 2011 1 次提交
  5. 04 9月, 2011 6 次提交
  7. 03 9月, 2011 1 次提交
    • M
      [media] dvb-core, tda18271c2dd: define get_if_frequency() callback · 8513e144
      由 Mauro Carvalho Chehab 提交于 
      Tuners in general convert a high frequency carrier into an Intermediate
Frequency (IF).

Digital tuners like tda18271, xc3028, etc. generally allow changing the IF
frequency, although they generally have recommented settings for the IF.
Analog tuners, have a fixed IF frequency, that depends on the physical
characteristics of some analog components.

For digital tuners, it makes sense to have ways to configure IF,
via the tuner's configuration structure, like what's done inside the
tda18271-fe maps.

The demods need to know what IF is used by the tuner, as it will need
to convert internally from IF into baseband. Currently, the bridge driver
needs to fill a per-demod configuration struct for it, or pass it via
a dvb_attach parameter.

The tda18271 datasheet recommends to use different IF's for different
delivery system types and for different bandwidths.

The DRX-K demod also needs to know the IF frequency in order to work,
just like all other demods. However, as it accepts different delivery
systems (DVB-C and DVB-T), the IF may change if the standard and/or
bandwidth is changed.

So, the usual procedure of passing it via a config struct doesn't work.

One might try to code it as two separate IF frequencies, or even as a
table in function of the delivery system and the bandwidth, but this
will be messy.

So, it is better and simpler to just add a new callback for it and
require the tuners that can be used with MFE frontends like drx-k
to implement a new callback to return the used IF.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: NAntti Palosaari <crope@iki.fi>
      8513e144
  9. 27 8月, 2011 2 次提交
  11. 06 8月, 2011 1 次提交
  13. 29 7月, 2011 1 次提交
    • M
      [media] tda18271c2dd: Fix saw filter configuration for DVB-C @6MHz · cf845297
      由 Mauro Carvalho Chehab 提交于 
      Currently, the driver assumes that all QAM carriers are spaced with
8MHz. This is wrong, and may decrease QoS on Countries like Brazil,
that have DVB-C carriers with 6MHz-spaced.

Fortunately, both ITU-T J-83 and EN 300 429 specifies a way to
associate the symbol rate with the bandwidth needed for it.

For ITU-T J-83 2007 annex A, the maximum symbol rate for 6 MHz is:
	6 MHz / 1.15 = 5217391 Bauds
For  ITU-T J-83 2007 annex C, the maximum symbol rate for 6 MHz is:
	6 MHz / 1.13 = 5309735 Bauds.

As this tuner is currently used only for DRX-K, and it is currently
hard-coded to annex A, I've opted to use the roll-off factor of 0.15,
instead of 0.13.

If we ever support annex C, the better would be to add a DVB S2API
call to allow changing between Annex A and C, and add the 0.13 roll-off
factor to it.

This code is currently being used on other frontends, so I think we
should later add a core function with this code, to warrant that
it will be properly implemented everywhere.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
      cf845297
  15. 28 7月, 2011 26 次提交