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

Manu Abraham abraham.manu at gmail.com
Mon Oct 15 16:34:22 CEST 2007


Johannes Stezenbach wrote:
> On Mon, Oct 15, 2007, Manu Abraham wrote:
>> Johannes Stezenbach wrote:
>>> 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.
> 
> That doesn't contradict what I said at all.
> 
> E.g. the HDTV TS is packaged with ISI 0x23 and the SDTV has ISI 0x42.
> The ISI for each TS is in the EN 300 468 S2 delivery desc.
> 
> When receiption conditions are good you can receive both TSs,
> when they are bad you can only receive the SDTV TS (the HDTV
> one will have too many errors).
> 
> In all cases the output of the demod is a single TS.

That's not what i mean to state: there are 2 methods.

* Output Back Off method (OBO)
(this uses ACM)

The method assumes IBO on-board the satellite adjustable on a 
frame-by-frame basis according to the transmitted modulation format 
to provide the maximum capacity that can be supported by ACM systems.

(basically used for feeds.)

* Hierarchical modulation
(This uses CCM)

http://linuxtv.org/wiki/index.php/Image:Hmod.jpg

Since you are very confident, so which of these two do you think are implemented 
on the Hotbird 9 satellite ?


Manu



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