[linux-dvb] dvb-h demodulator commercially available and supported by linux driver?!

Patrick Boettcher patrick.boettcher at desy.de
Thu Nov 10 18:29:38 CET 2005


Hi Andrea,

Andrea Venturi wrote:
> hi,
> 
> here in italy, many dvb-h trials are springing all over..
> 
> i'm wondering if there's already a dvb-h compliant (at least supporting
> 4k) demodulator available on the market, and with a linux driver ready..

As far as I know, the DVB-H trials in the air are always using 8k or 2k. 
I don't remember why (I just forgot it) but someone told me that there 
is no real need to use 4k.

> for example i know the dibcom family:
> 
> http://195.137.248.72/539_Dibcom/Website/site/eng_accueil_applicationsproducts_products_chipset.htm
> 
> in this table, i can see both dibcom dib7000-h dib7000-m are supposed to
> be "dvb-h" compliant

That is correct.

The DiB7000 was at first just used for DVB-H and currently DiBcom is 
also using this demod for DVB-T devices (because power consumption is 
lower with this design and there is also the DiB7700 and DiB7710 which 
is demod and USB/PCI bridge in one chip - devices are really small).

> i've just checked in linux-dvb CVS, and actually there's nothing about
> these chips, but there is already the dibcom3000mc driver, so, maybe the
> path is ready, but, if i can elaborate, the registry actually carries
> just one bit for the transmission mode (switching from 2k - 8k)

Yes, Dib3000* was the previous version of the demod created by DiBcom 
and at that time there was no 4k FFT.

The DVB-H testsignal in Berlin was/is transmitted with 8K and I was 
successfully using DVB-T device to receive the DVB-H signal.

> anyway, do you know if this dvb-h thing is going to run (soon or later)
> on linux devices?

DVB-H is a bit more than DVB-T + 4k-mode:

The main differences/additions (from memory):

- every data transmitted with DVB-H is encapsulated in IPv6 MPE sections
- a sophisticated RS FEC is used for error correction of the MPE-sections
- 4k-mode

Afaiu, the used RS-FEC cannot be simulated by a normal CPU - because it 
is too hard - so you need a dedicated IC to do the work - thus the MPE 
sections have to be processed by the hardware and what you get out of 
the hardware a IPv6 packets. Anyway, the RS-FEC is mostly necessary to 
get good data while moving around - for local reception MPE-FEC might 
not be necessary.

> do you know of a ready available HW (PCMCIA/USB) external adapter for pc?

No. DiBcom has SDIO cards for DVB-H which are delivered along with a 
SDK. Don't know the price.

You can use a slightly modified dvb-net.c, your dvb-t receiver and some 
application doing the multicast-joins automagically to simulate dvb-h 
with current dvb-kernel. For the DVB-H test in Berlin (I don't know if 
it is still on air) it was working. Unfortunately I didn't have a 
h264-decoder...

regards,
Patrick.



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