[linux-dvb] DVB-S2 Multiple logical TS on the same frequency
abraham.manu at gmail.com
Mon Oct 15 01:49:29 CEST 2007
Johannes Stezenbach wrote:
> 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:
> 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.
If the demod was to filter Multiple streams automatically, it will mean
something like choosing all the options in a multiple choice question,
where you are supposed to choose one.
I can't see anyway how the demod can select the streams that which
you are interested in, without the user telling it what you want.
> 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
> 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.
Maybe, not very sure on that. Also the specifications additionally adds this:
5.2 SDTV and HDTV broadcasting with differentiated channel protection
The DVB-S2 system may deliver broadcasting services over multiple Transport Streams,
providing differentiated error protection per multiplex (VCM mode) (see note). A typical
application is broadcasting of a highly protected multiplex for SDTV, and of a less
protected multiplex for HDTV. Figure 17 shows an example configuration at the transmitting
side. Assuming to transmit 27,5 Mbaud and to use 8PSK 3/4 and QPSK 2/3, 40 Mbit/s
would be available for two HDTV programmes and 12 Mbit/s for two-three SDTV programmes.
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