[linux-dvb] DVB-S2 Multiple logical TS on the same frequency

Johannes Stezenbach js at linuxtv.org
Mon Oct 15 01:00:34 CEST 2007


On Sun, Oct 14, 2007, Manu Abraham wrote:
> 
> You can have MIS in 2 cases again:
> 
> 1) Transport Streams
> 
>  a) When it is SIS, it is similar to our normal DVB-S transmissions
>  b) When it is flagged MIS in the Baseband Header, we have Multiple Streams.
>      When it is MIS, if the logical streams are scrambled, we will need to route the relevant 
>      stream to the CA module, which means we have some additional job at the demuxer level.
>      (this will be a bit of  headache, coupled with a CA device)
> 
> 2) Generic Streams (note this need not be a MPEG2 stream at all)
>     This at least we can pipe everything to userspace at least as a last resort.
> 
> Temporarily, we do not need to worry about Generic streams (Single or Multiple), since they 
> aren't basically used in the broadcast profiles, _but_ MTS might be.

ACK -- see old posting:
http://article.gmane.org/gmane.linux.drivers.dvb/26040

However, contrary to what is written there I believe the demod
recognizes SIS vs. MIS and dis/enables the stream filter automatically.
I guess if you fail to set the correct ISI for MIS, you get no
output (or the wrong one). For SIS the stream id filter is irrelevant,
you can set it to any value.

IMHO all you need is to add an u8 input_stream_identifier
to struct dvbs2_params. You take the value and write it
in a demod register -- done.

You can get the input_stream_identifier (ISI) from the
S2 satellite delivery system descriptor, see EN 300 468.

(In the worst case the demod wouldn't en/disable the stream id
filter automatically, so you'd need to read SIS/MIS flags
from a register after tuning and do it manually -- but that's
all internal to the driver and not in the API. I think.)

(BTW, ARIB has a similar feature, transport_stream_id, see
http://linuxtv.org/cgi-bin/viewcvs.cgi/dvb-kernel-v4/linux/include/linux/dvb/frontend.h?rev=1.20.2.2&only_with_tag=ARIB_extension&view=auto
)


I'm very confident the output of the demod is a single TS in all
cases, and this has nothing to do with the demux.


Regards,
Johannes



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