[linux-dvb] Low symbol rates on FF DVB cards

Klaus Schmidinger Klaus.Schmidinger at cadsoft.de
Sat Dec 3 16:52:11 CET 2005


Oliver Endriss wrote:
> Klaus Schmidinger wrote:
> 
>>Full featured DVB cards (Siemens/Technotrend AV7110 design)
>>apparently have trouble with receiving channels at very low
>>symbol rates.
> 
> 
> Rev 1.6 cards (Grundig tuner) are known to have trouble with low symbol
> rates. Never heard about problems with other revisions.
> 
> 
>>An example is 
>>
>>   TVS Teleport Bonn;DMV:11535:vC34:S1.0W:5632:308+8190:256=eng,257=eng:0:2:1:65535:1:0
>>
>>with a symbol rate of 5632 (that transponder isn't always on, though).
>>
>>My FF DVB card can't receive this channel, so I have to receive it
>>with a budget card, which is able to handle this symbol rate.
>>
>>In order to automate this I tried getting the dvb_frontend_info
>>and checked its symbol_rate_min, hoping that I could use this
>>to find out whether a given device could receive a channel with
>>a given symbol rate.
>>
>>Unfortunately both my FF card and my budget card report the same
>>minimum symbol rate:
>>
>>  name Alps BSRV2
>>   type 0
>>   frequency_min 950000
>>   frequency_max 2150000
>>   frequency_stepsize 250
>>   frequency_tolerance 29500
>>   symbol_rate_min 1000000
>>   symbol_rate_max 45000000
>>   symbol_rate_tolerance 0
>>   notifier_delay 50
>>   caps 0x000006AF
>>
>>  name STV0299/TSA5059/SL1935 based
>>   type 0
>>   frequency_min 950000
>>   frequency_max 2150000
>>   frequency_stepsize 125
>>   frequency_tolerance 44000
>>   symbol_rate_min 1000000
>>   symbol_rate_max 45000000
>>   symbol_rate_tolerance 500
>>   notifier_delay 0
>>   caps 0x400006AF
>>
>>So I'm afraid I can't use this to make that decision.
>>
>>Is there anything else I could use, or do I just have to
>>check for the existence of a video and audio device (which
>>indicates that there is an MPEG decoder) and in that case
>>refuse to switch to a channel with a symbol rate of, say,
>>less than 10000 (in VDR's channels.conf notation)?
> 
> 
> Either symbol_rate_min is wrong for your FF card (Rev 1.3?) or the

Yes, it's a Rev 1.3 FuSi card (sorry, I forgot to mention that).
Note that I'm using the DVB driver on kernel 2.4. However, I
didn't see anything in the dvb-kernel source that would indicate
that something has been fixed in that area since the old driver.

> driver is broken for low-symbol rates.
> Anyway, we have to fix the driver.
> 
> Is there any low-symbol-rate FTA channel on 19.2E or 13E?

I didn't find one on either of these positions, but there is one
on S28.5E:

ManToVa Puntosat:12546:vC34:S28.5E:2893:512:513:0:0:1:0:0:0

I just tried tuning to this one with my FF card and got no picture
or sound. With my budget card I can receive it.

Klaus



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