Hellou
I saw there is nowadays logic in dvb-frontend which calculates
bandwidth_hz value in cache. Calculation formula seems to be correct.
But that makes me wonder if that is wise as it gives occupied bandwidth
instead of nominal. For example I have typical DVB-C annex A, 8 MHz
bandwidth, symbol rate 6875000 and roll-off factor 0.15. That gives
calculation result is 7 906 250 Hz for nominal 8 000 000 Hz channel.
This value is used only by tuner. Only visible effect is thus every
tuner driver should use if statement to compare to find out nominal
value as tuner chips usually configures low-pass filter steps of 8/7/6/5
MHz.
For me it sounds better if tuner just gets nominal bandwidth - maybe
calculating real used bw could be nice too as it is possible to return
userspace.
Shortly: I see it better to give nominal RF channel value for tuner.
regards
Antti
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http://palosaari.fi/
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