[linux-dvb] DVB API update

Wolfgang Wegner wolfgang at leila.ping.de
Sat Sep 15 22:17:28 CEST 2007


how should this discussion take place?

Up to now, my personal experience showed only some drawbacks in the
frontend API, and reading the current proposal v4_0.3 I have some
comments/questions concerning this part:

- dvb_fe_type: DVB-S2 is missing and I personally would also like
  to see ASI here...
- frontend status:
  - BER is lacking a proper definition (to which base is it calculated?)
  - signal strength: same problem, what are the ranges?
  - snr: again, no base and ranges given

For signal strength and snr, I already wrote about a possible partly
solution: provide a means to query the frontend for corresponding min
and max values (in dvb_frontend_info?).

I know signal strength is very unreliable for most frontends (are silicon
frontends really better, as claimed from time to time?), but at least
the snr can be calculated very good for most demodulators. Would it be
possible to do this calculation somewhere "near the driver" to provide
a uniform value to the caller regardless of the frontend actually used?

I understand floating-point is not possible in the kernel, but what
other possibilities are there to get rid of the device-dependent snr
calculation in the application? Please, no debate about complete user-space
driver here! I really hope there are other solutions, but I have no idea
what is possible.

Best regards,

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