1. 29 7月, 2011 1 次提交
    • M
      [media] tda18271c2dd: Fix saw filter configuration for DVB-C @6MHz · cf845297
      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
  2. 28 7月, 2011 39 次提交