[linux-dvb] [PATCH][RFC] dvb-s2 support added to frontend.h

Trent Piepho xyzzy at speakeasy.org
Thu Mar 30 23:51:42 CEST 2006


On Thu, 30 Mar 2006, Manu Abraham wrote:
> Marcel Siegert wrote:
> >>> +#define dvb_qpsk_parameters dvb_dvbs_parameters
> >>> +#define dvb_qam_parameters dvb_dvbc_parameters
> >>> +#define dvb_ofdm_parameters dvb_dvbt_parameters
> >>>
> >> Might as well add vsb==atsc.
> >>
>
> ATSC is 8VSB modulation.
> What you say "QAM" is annex-b digital cable TV. Some people call it clean QAM.

The way you tune ATSC (terrestrial or cable) now is by setting modulation
from:

struct dvb_vsb_parameters {
        fe_modulation_t modulation;  /* modulation type (see above) */
};

For terrestrial you set it to VSB_8, for cable you set it to QAM_256.

Most frontends now days can do both, some older frontends can only do 8/VSB.

I think changing struct dvb_vsb_parameters to dvb_atsc_parameters makes a lot
of sense.  Now you have this:

fe_params.u.qam.modulation = QAM_256;  // Wrong!

fe_params.u.vsb.modulation = QAM_256   // Right!

That's just messed up.



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