[linux-dvb] Q2: dvb api 3 - FE_ATSC

Patrick Boettcher patrick.boettcher at desy.de
Mon Aug 22 22:20:51 CEST 2005


On Mon, 22 Aug 2005, Rainer.scherg wrote:

> Next question: ;-)
>
> looking on:  * frontend.h   (cvs 1.18)
>
> [...]
> typedef enum fe_type {
> 	FE_QPSK,
> 	FE_QAM,
> 	FE_OFDM,
> 	FE_ATSC
> } fe_type_t;
> [...]
>
> I do not understand FE_ATSC here,
> because QPSK, QAM QFDM are modulations.
> Why is FE_ATSC here?

In the same sense that there is FE_OFDM. COFDM uses QPSK, or QAM16 or 
QAM64 modulations.

> ATSC supports several modulations...
> Shouldn't there be the modulation named  (e.g. VSB)?

No, because an ATSC demodulator is capable of decoding VSB and QAM 
signals.

QAM in the US is ITU J83 Annex-B.  Europe's DVB is Annex-A.  Asia is Annex 
C.

> Next:
> Currently this is an enum field, but what happens
> if you are having a frontend supporting more than one modulation?
> (e.g. DVB-CT  -->   FE_QAM|FE_OFDM )

DVB-T is much too different to DVB-C. When this will happen, you'll 
probably make two different frontend-dev-nodes with separate parts in 
the one driver.

regards,
Patrick.

--
   Mail: patrick.boettcher at desy.de
   WWW:  http://www.wi-bw.tfh-wildau.de/~pboettch/




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