On 09/06/2020 16:31, Marc Gonzalez wrote: > On 08/06/2020 17:30, Marc Gonzalez wrote: > >> Suppose we know that several channels are transmitted on a given frequency >> by terrestrial antenna. However, we don't know if the signal is "encoded" >> (not sure this is the right term) in DVB-T or DVB-T2 modulation. >> >> Do we have to scan the frequency /twice/ >> first with DTV_DELIVERY_SYSTEM = SYS_DVBT >> then with DTV_DELIVERY_SYSTEM = SYS_DVBT2 ? >> >> Or is there some optimization where both modulations are handled >> in a single step? >> >> Or maybe it depends on the tuner driver? > > Digging a bit deeper... > > My system sports a Silicon Labs Si2168 DVB-T2/T/C demodulator > > The data sheet states: > > "For DVB-T2 and T2-Lite: > DVB-T2 versus DVB-T automatic detection" > > "In DVB-T and DVB-T2 reception, parameters necessary for device synchronization > are broadcast in the transmission parameters (respectively TPS and P1 symbol). > When these transmission parameters are found and decoded, the demodulator is > automatically and accordingly configured to achieve full synchronization." > > > This HW is supported upstream by drivers/media/dvb-frontends/si2168.c > https://elixir.bootlin.com/linux/latest/source/drivers/media/dvb-frontends/si2168.c > > I have a nagging feeling because si2168_set_frontend() appears to > behave differently for SYS_DVBT and for SYS_DVBT2... > > https://elixir.bootlin.com/linux/latest/source/drivers/media/dvb-frontends/si2168.c#L250 > https://elixir.bootlin.com/linux/latest/source/drivers/media/dvb-frontends/si2168.c#L297 > https://elixir.bootlin.com/linux/latest/source/drivers/media/dvb-frontends/si2168.c#L345 > > Maybe setting SYS_DVBT2 would also work for DVB-T transmissions? > (TODO: test that) > > Any insight would be greatly appreciated. FTR, on IRC, Brad pointed out this patch of his: https://patchwork.kernel.org/patch/10744999/
