>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. So let's assume different streams (with different modcods) are transmitted. In this case we just need to set the modcod according to the desired stream. -> The other streams (with other modcods) will be ignored! There is no way to receive more than one stream at once ... > >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 "This descriptor is only required if DVB-S2 is not used in normative broadcast mode (NBC-BS). In normative broadcast mode the satellite_delivery_system_descriptor is sufficient." The S2 descriptor is the only descriptor providing SISMIS. According to EN 302 307 there are exactly two modes: NBC-BS and BC-BS. "required if not NBC-BS" -> "required if BC-BS" -> SISMIS only available in BC-BS Christoph _______________________________________________ linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
