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

Patrick Boettcher patrick.boettcher at desy.de
Wed Feb 15 14:53:18 CET 2006


Hi Johannes,

On Wed, 15 Feb 2006, Johannes Stezenbach wrote:
>> 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 seems to me that a parameter is missing in the Linux DVB API
> to select between the high/low priority stream. If I understand
> it correctly the hierarchy mode just modifies the modulation scheme,
> and you still need a seperate knob to select which TS (high or low)
> the frontend should output. Can someone confirm this?

I think the hierarchy-field contains actually two values:

If hierarchy is used and what is the values for alpha. Or what does 
1,2 and 4 mean?

If that is the case: I think we don't need to change: HIERARCHY_NONE could 
mean get the high priority stream and HIERARCHY_1 and the others: get lp 
stream with an appropriate alpha.

If my understanding is correct and we agree on a change of the API, IMHO, 
it would be better like this.

Dividing the HIERARCHY_NONE _1, _2 and _4 in two different tuning 
parameters:

one field for: SELECT_HP, SELECT_LP
one field for: ALPHA_1, ALPHA_2, ALPHA_4

Afaik: by default in a non-hierarchical transmission the alpha is always 1 
(that is where it clashes with HIERARCHY_NONE, I remember once having 
difficulties with that).

What do you think?

regards,
Patrick.

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



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