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captain jack
06-09-12, 22:02
Hi,

As we all know, the Vu boxes do not provide a SNR value in dB but always in percentage. This is something to do with drivers.

Now, I have checked my friend's Dreambox 800HD receiver and compared the dB value and the percentage value to find a correlation. The correlation seems to be SNR dB = SNR% / 6.21 which gives a more or less accurate conversion.

So, if my SNR% on the Uno is 34%, which is a just about watchable picture, it converts to SNR dB of around 5.47dB which sounds about right. I *know* that this value shouldn't be taken as gospel and it's purely an indication etc. but I was wondering if it's possible for the VIX team to calculate the dB from the percentage SNR?

I have played around with OpenWebIF and edited the signal.py file like the following:

\t<e2snrdb> ''')
_v = VFFSL(SL,"snr_db",True) # u'$snr_db' on line 4, col 12
_v = round(_v/6.21,2)
if _v is not None: write(_filter(_v, rawExpr=u'$snr_db')) # from line 4, col 12.
write(u''' dB </e2snrdb>
\t<e2snr> ''')

After restarting Engima, my http://uno/web/signal changed from:

<e2frontendstatus>
<e2snrdb>42 dB</e2snrdb>
<e2snr>42 %</e2snr>
<e2ber>0</e2ber>
<e2acg>65 %</e2acg>
</e2frontendstatus>

to

<e2frontendstatus>
<e2snrdb>6.76 dB</e2snrdb>
<e2snr>42 %</e2snr>
<e2ber>0</e2ber>
<e2acg>65 %</e2acg>
</e2frontendstatus>

This helps for windows based apps which use this path to get signal levels but skins seem to take this information from somewhere else.... So, er.... where? :) skin.xml seems to look at "FrontendInfo" but I am not sure how I can use skin.xml to change values....

Any advice/ideas/criticisms?

CJ
Rob van der Does
07-09-12, 05:59
STB's are no signal meters. The SNR-read out, whether in % or dB, is always just a value, not calibrated at all. Good for comparison using one and the same box when e.g. aligning a dish, but not for comparing values between boxes.
So what would be the use of using this not-calibrated value of a Dreambox to convert the percentage-read out of a VU-box?
The percentage read-out can be used for the very same purpose as any dB-read out: aligning a dish, comparing the SNR of several transponders and see if a transponder has it's usual value in case of disturbed reception. Nothing more, nothing less.

So percentages are fine; might even call them cows; its the numerical value that counts.
captain jack
07-09-12, 07:51
Rob, it's nothing more than a matter of personal preference of how I want my values represented. Same sort of preference as how you want your skin to look.

All I am asking is where I can change the representation of SNR read-out on the Infobar - that's all.
irishchris
07-09-12, 08:40
As far as i remember this option has already been coded into the image. Setup/system/customise off the top of my head. Will check later when home for correct location of this option for you

Sent from my GT-I9300 using Tapatalk 2
captain jack
07-09-12, 08:48
Yeah, there's an option in System > OSD > Settings but it doesn't change one from the other.
irishchris
07-09-12, 08:50
Correct location is menu/setop/system/osd/settings and change infobar reafout from snr to db. Reboot and should then be displayed in db in infobar

Sent from my GT-I9300 using Tapatalk 2
irishchris
07-09-12, 08:52
Yeah, there's an option in System > OSD > Settings but it doesn't change one from the other.

After changing the setting , did you restart your reciever?

Sent from my GT-I9300 using Tapatalk 2
Rob van der Does
07-09-12, 11:41
Yeah, there's an option in System > OSD > Settings but it doesn't change one from the other.
Correct: most drivers don't support that. so they will always show the same figures, whatever choice has been made.