On Thu, May 25, 2006, christophpfister@xxxxxxxxxxx wrote: > >> Johannes Stezenbach wrote: > >-> this would mean that modulation and fec are the same > > for DVB-S and DVB-S2 > > (however, thanks to the MODCOD field in the DVB-S2 > > PLHEADER it would probably work with different > > mod/fec, too, as the demod can figure it out automatically) > > Yes, But another rolloff may be used (in v1.5.1 there are reserved values > at #modulation which are used now). > > >(Indeed, I believe the modulation and fec fields in > >struct dvbs2_params are not necessary -- the values > >can change on a per-frame basis anyway, says the spec.) > > They are necessary! It's possible that the transmitters sends more than one > stream (with VCM / TDM), but you have to specifiy the modcod for the stream > you want to receive. In MIS mode both streams can have different mod/fec. However, I don't see any per-stream_id mod/fec registers in the STB0899 data sheet, and certainly you don't imply there's an API call necessary per received frame to change the settings? Really, IMHO the only way this can work is if the demod can read MODCOD from PLHEADER and reconfigure mod/fec automatically per frame. And if it can do it for MIS, it can do the same for SIS. (And indeed, the STB0899 data sheet has seperate registers for BBHEADER and PLHEADER fields extrated from the stream, and ones where you can supply your own values. The description is vague but talks about "forcing" your own values. This might mean that this is just a test/debug feature and not necessary for normal operation. *Add a BIG questionmark here.*) > >For NBC-BS in MIS mode however, I think two or more > >S2 descriptors are needed, one for each stream_id. > > There can't be any NBC-BS in MIS mode (see above). > > >A channel scan and the channels.conf file must thus > >be prepared to handle this. > >IOW, it is not sufficient to add parsing of the S2 descriptor > >to dvbscan, because dvbscan assumes that there is > >only one set of parameters per *frequency*. There > >is more work necessary. For BC-BS and for MIS > >dvbscan would also have to FE_SET_PARAMS multiple > >times to can all streams. > > It has to scan LP and HP streams if available (but this case is detectable). > But IMHO this question is independent from the API thread and shouldn't be > discussed here. There will be changes to the initial tuning file and the > channels.conf file of course. See my other mail, EN 302 307 table 1 says (well, I interpret it that way), that MIS is an optional feature of NBC-BS, and IMHO has nothing to do with BC mode. Johannes _______________________________________________ linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
