SergioDanielG Wrote:Ok, thanks very much.
And question... When do you will add blindscan support for linux?
Thanks again
Best regards
There is already blindscan capability in TBS Linux driver,but to make full use it, you need to write a 'shell-script' which consists of several simpler steps.
In Windows primary reason that special tool for blind-scan is needed is because there is no standard way to get-back from the driver the details about
the locked frequency during the blind-scan, but in Linux that's part of the Linux DVB API and the function with which you can get back the signal parameters and details from the driver is called 'get_frontend' and you can call with it many tools (i.e. without need to program in any language) - for example:
# dvbsnoop -adapter 1 -s feinfo
in fact TBS Linux drivers are the only DVB-S2 drivers that implement full support for 'get_frontend' Linux DVB API function. So, if you haveLinux driver that doesn't implement 'get_frontend' Linux DVB API function (i.e. you use no TBS hardware) then like in Windows you will need special tool for blind-scan even if the hardware can do blind-scan, otherwise (when implementation of 'get_frontend' Linux DVB API function is in place like in case of TBS drivers) you can use 'shell-script', because blind-scan consists of few simple steps every one of each can be done with single command line:
0) for any frequency in the range X,Y with step of Z MHz:
1) send tune request to frequency T (for example that can be done with 'szap-s2' tool)
2) check the lock status with calling 'get_frontend' Linux DVB API function and in case of lock that will give you all signal parameters
(for example it can be done with 'dvbsnoop' command line i gave above), i.e. effectively result in what blind-scan is supposed to do for you - then you report with all details for all frequencies on the satellite that exist and can be locked
and since those steps above require only command lines involving ready tools : 'szap-s2' and 'dvbsnoop' they can be automated in 'shell-script'. so, more experienced Linux users already wrote such 'shell-scripts' for themselves and use blind-scan that way.
Since not so experienced linux users will have difficulty in writing this "shell-script" by themselves, we will prepare such 'shell-script' and include it in the next driver release for easy use of every Linux user.
But before you can use blindscan on Linux, you will still need to have one of dvb card which has hardware built-in blindscan feature,eg. TBS6925,TBS6921,TBS6922,TBS6928,TBS8921,TBS8922,TBS5921,TBS5922.
- for blind-scan you always need to do 4 passes: Vertical, 22 kHz off; Horizontal 22 kHz off; Vertical, 22 kHz On; Horizontal 22 kHz On
- PIDs required by 'szap-s2' could be fake like "1:1:1", 'szap-s2' doesn't require the real PIDs to get signal lock
- all other parameters as symbol-rate, code-rate, roll-off, signal inversion, delivery system and mode (or modulation) are ignored, i.e. they are not really used and instead auto-detected - that's exactly the purpose of 'get_frontend':
# dvbsnoop -adapter 1 -s feinfo
it returns the actual parameters of the locked signal and not the parameters used during the tune requests. so, to make it more clear example: you can sent tune requests via 'szap-s2' with symbol-rate of 40000, code-rate of 3/4, roll-off of 0.20, signal inversion On, delivery system S2 and mode QPSK then get lock even those are completely wrong, because blind-scan capable hardware can auto-detect them in hardware and when do:
# dvbsnoop -adapter 1 -s feinfo
get that in reality the signal with symbol-rate of 22000, code-rate of 2/3, roll-off of 0.25, signal inversion Off, delivery system S2 and mode 8PSK, i.e. something completely different than your initial tune request. so, that's the point of blind-scan capable hardware - it only needs polarization (V or H) for proper LNB power, 22 kHz On/Off for proper band and some frequency to try - all other signal parameters could be "fake" and the real one can be obtained after the blind-lock is acquired using 'get_frontend'.
Posted: Tue Aug 23, 2011 11:46 am