[linux-dvb] DVB-T devices supporting hierarchical mode?

Patrick Boettcher patrick.boettcher at desy.de
Wed Feb 15 10:09:08 CET 2006


Hi Mauro,

On Tue, 14 Feb 2006, Mauro Borghi wrote:
> For the first time here in Torino, RAI (Italy's public television 
> broadcaster) is broadcasting an experimental DVB-T channel, featuring in high 
> definition the Olympic Winter Games.
>
> They are exploiting *hierarchical* modulation, in order to accomodate -in the 
> same radio channel- both a DVB-H test stream and this HDTV stream.
> The low bitrate DVB-H stream is the "high priority" stream, while the HDTV 
> stream (H.264/AVC) is the "low priority" one.
>
> From the information I got from devices supporting hierarchical mode, tuning 
> data are as following:
>
> RAIHD:538000000:INVERSION_OFF:BANDWIDTH_8_MHZ:\
> FEC_1_2:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:\
> GUARD_INTERVAL_1_8:HIERARCHY_2:x:x:x

Very interesting. I would have never thought that they will use 
hierarchical transmission in the real world, but anyway.

> [intro end]
>
> Do you know about LinuxDVB-supported devices which are known to support 
> hierarchical modulation?
> Is it meant to be sufficient setting HIERARCHY_2 in the struct passed to the 
> frontend device when tuning, in order to select the LOW priority stream?

Although it was most likely never tested with most of the demod-drivers in 
linux-dvb it should be possible with all of them.

> From the tests I did with a Twinhan 7045 USB2 clone (from digicom), the 
> device seems to always lock on the HIGH priority stream, no matter what 
> params are passed!

The Twinhan box has a MT352 inside and the controlling is done inside the 
FX2 USB firmware. As hierarchical transmission has significant drawbacks 
when used and no one (not even Twinhan :) ) expected that to be used 
anywhere, they don't have it implemented. Ie. there is no way to give this 
information to the firmware.

It would be interesting to see how devices perform.

As far as I can see, maybe too optimistic, only the vp7045 and 
dtt200u-driver (Twinhan and Wideview Clones) are definitely not supporting 
the reception of hierarchical transmissions. Every other DVB-T demodulator 
driver has at least the option to set (if the hardware works is another 
question).

I know that hierarchical transmissions are working with DiBcom 
demodulators. Maybe the current dib3000mb/mc driver is not doing it 
correctly, but the hardware works - in that case I could help to fix the 
driver.

best regards,
Patrick.

--
   Mail: patrick.boettcher at desy.de
   WWW:  http://www.wi-bw.tfh-wildau.de/~pboettch/



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