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Dvbstream has inadequate tuning options and misleading help prompt #2

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dikonov opened this issue Oct 14, 2024 · 0 comments
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@dikonov
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dikonov commented Oct 14, 2024

Please, correct me if I am wrong, but it seems that dvbsream cannot tune and record a raw DVB stream with the following parameters (which cannot be changed by me):

  • card 0 [/dev/dvb/adapter0]
  • frontend 2 [/dev/dvb/adapter0/frontend2] = "tuner C" in Еnigma2 GUI terms
  • DISEqC 1.1 input 7 (I still have an option to use an old diseqc 1.0 with extra effort)
  • freq 12226000 (in Hz, as instructed by the help prompt)
  • polarization LeftCircular

Dvbstream has no options to specify:

  1. frontend number 2.
    My box (Sezam Marvel, running OpenATV 7.4) has 4 physical tuners, connected to different antennas with different diseqc switches. Enima2 GUI labels them as ABCD. I need tuner "C". At the system level I have only one dvb adapter #0 [/dev/dvb/adapter0] and 4 frontends [/dev/dvb/adapter0/frontend0-3]. How do I make dvbstream switch to frontend 2 ???

  2. diseqc 1.1 input
    My diseqc switches are 1.1 and have 8 and 16 inputs. Dvbstream has no capability to control diseqc inputs and fails to tune the signal. I can circumvent this by using the 1.0 mode but it is bad.

  3. circular polarization
    Dvbstream does not recognize L and R as valid values for the -p option. I know that they can be substituted with H or V, but it is not clear which is which. The help prompt should give a hint.

  4. frequency value
    The help instructs me to supply the -f option with a value of the freq in Hz. In my case it is 12226000 - the transponder frequency. However, it is wrong, as I get this error:

root@sezammarvel:~# ./dvbstream -f 12226000 -p H -s 27500 -cr 3_4  -n 60 -o:trico.ts
dvbstream v0.5 - (C) Dave Chapman 2001-2004
Released under the GPL.
Latest version available from http://www.linuxstb.org/
Using DVB card "DVB-S2 NIM"
tuning DVB-S to L-Band:0, Pol: Srate=27500000, 22kHz=off
ERROR tuning channel
: Invalid argument

Why does it say "tuning DVB-S to L-Band:0" instead of "tuning DVB-S to12226000 Hz" ?
The path of trial and error leads to this:

root@sezammarvel:~# ./dvbstream -f 12226 -p H -s 27500 -cr 3_4 -c 0 -n 60 -o:trico.ts
dvbstream v0.5 - (C) Dave Chapman 2001-2004
Released under the GPL.
Latest version available from http://www.linuxstb.org/
Using DVB card "DVB-S2 NIM"
tuning DVB-S to L-Band:2141700760, Pol:H Srate=27500000, 22kHz=off
polling....
Getting frontend event
FE_STATUS:
polling....
FE_STATUS:
polling....
^CFE_STATUS:

Since the value in Hz is rejected as too large, I tried the same in Mhz and got an endless loop of "FE_STATUS: polling...." which cannot be interrupted with Ctrl+C.
Then I figured out that the L-band freq is the frequency after LNB. The LNB has LOF 10750, so I tried "-f 1476"

 ./dvbstream -f 1476 -p H -s 27500 -cr 3_4 -c 0 -n 60 -o:trico.ts
dvbstream v0.5 - (C) Dave Chapman 2001-2004
Released under the GPL.
Latest version available from http://www.linuxstb.org/
Using DVB card "DVB-S2 NIM"
tuning DVB-S to L-Band:2145818664, Pol:H Srate=27500000, 22kHz=off
polling....
Getting frontend event
FE_STATUS:
polling....
Getting frontend event
FE_STATUS: FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI FE_HAS_SYNC
Bit error rate: 0
Signal strength: 59636
SNR: 22937
FE_STATUS: FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI FE_HAS_SYNC
Output to stdout
Streaming 0 streams

It tunes to something and locks a signal! But it receives NOTHING. Nothing is written to to the file trico.ts. Meanwhile this transponder works perfectly and I can tune to it and watch the FTA InfoChannels there.

I do not understand the "tuning DVB-S to L-Band:2145818664" part. What is the actual frequency it sets the hardware to? Is it really 12226 Mhz (LNB) | 1476 Hz (tuner) ?

The help and readme must be very clear about frequency specification, but they provide no information.

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