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wejones

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Reply with quote  #1 
  For the past couple days, I've been experimenting with a few things, such as DSS on PROF and TBS receivers, and had been changing a few parameters in the streamreader.ini in the Crazyscan directory.  Today, I tried to lock a DVB-S2 transponder on my (half broken) TBS 6983. The Crazyscan spectrum looked fine, and I locked a DVB-S2 signal with about 14db signal, however when I'd stream to TSREADER, I got nothing but gibberish.  I looked back at the lock on Crazyscan, and although it was 14 db signal, I was getting a very high BER, which seemed strange. I tried re-booting the computer, but that didn't help.  So I assumed that my 6983 had completely died, and switched to my PROF-7500.  Pretty much the same thing there.  Switched to my 5927, and same thing.  I only had one more modern receiver left, my new TBS 5520, so I crossed my fingers, and tried that.  Worked fine.  Actually all 4 worked on DVB-S QPSK transponders, it was just the DVB-S2 8PSK signals that weren't working.
    But why would 3 of my 4 receivers just stop working on 8PSK all of a sudden.  I tried all sorts of things, but couldn't get the first 3 to work.  I had assumed that Crazyscan and TSREADER were OK, because they worked with the 5520.   But eventually, after a couple hours, I decided to look at Streamreader.ini, and I noticed that I had left a couple of the parameters in the mode I was testing, ie the DSS and the Frame Mode.  So I commented out those two settings, and sure enough, the 6983, 5927, and PROF came back to life.  I assume that it wasn't the DSS setting, since previously, I had left that enabled with no problems, so I'm assuming that it was the Frame mode setting that caused the problem. 
  I have no idea of what enabling Frame mode does, and why does it kill 3 of the receivers but not the 4th? Could it be that the 5520 doesn't have a frame mode to be enabled?
   In any event, I'm really happy that I hadn't killed those 3 receivers, but don't understand what happened.

 
majortom

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Reply with quote  #2 
Something to do with Long Frame / Short Frame?
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Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
DB8E/VHF Yagi rotor FM Bandstop ap-8700 preamp 8way split LG lcd.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html

wejones

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Reply with quote  #3 
Quote:
Originally Posted by majortom
Something to do with Long Frame / Short Frame?

Thanks.
I had to do a bit of googling to respond to this, because I never really had any understanding about this long frame vs short frame thing.  But from what I read, I get the impression that DVB-S frames are 188 vs ~131 for DSS (which is why I experimented with changing this parameter in the streamreader.ini file) vs the capability of having variable frame rates for DVB-S2?  So perhaps enabling this frame mode parameter might filter out frames that aren't 188 bytes, which might work well with a DVB-S signal, but would completely mess up a DVB-S2 signal since it was filtering out the short frames???  I guess that makes sense, however I don't understand why my TBS-5520 still seemed to work OK on the same transponders that didn't work at all on the other three receivers. Only way that makes sense (to me) is if the filtering is done in the receiver, and the 5520 doesn't have the capability of doing the filtering.  I also don't understand why one would want to filter out non-complying frames, except perhaps in ACM/VCM signals where there might be a fixed frame signal mixed with a variable frame signal, and this would help you obtain some reception of at least part of a signal??? 
   Also, I guess I'm assuming that this parameter ( frame mode =1 ) implies enabling the mode vs =0 implies not enabled, but perhaps there are different modes specifying different frame lengths??

Anyway, it's all beyond my understanding.


majortom

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Reply with quote  #4 
Relative to the INI setting in question... Keep in mind may be a difference between parameters/terminology used as presented in the standards
(eg ETSI) vs the parameters/terminology you see in the programs you use. Guessing the author can really answer your question with certainty.

Decent description of some parameters Long/Short Frame as presented in the ETSI standards...Without looking at the standards.
https://github.com/phase4ground/DVB-receiver/wiki/DVB-S2-FRAME-RATES

we don't wanna confuse the DVB TS / DSS TS Packet Size with frame size.

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Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
DB8E/VHF Yagi rotor FM Bandstop ap-8700 preamp 8way split LG lcd.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html

wejones

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Reply with quote  #5 
Quote:
Originally Posted by majortom
Relative to the INI setting in question... Keep in mind may be a difference between parameters/terminology used as presented in the standards
(eg ETSI) vs the parameters/terminology you see in the programs you use. Guessing the author can really answer your question with certainty.

Decent description of some parameters Long/Short Frame as presented in the ETSI standards...Without looking at the standards.
https://github.com/phase4ground/DVB-receiver/wiki/DVB-S2-FRAME-RATES

we don't wanna confuse the DVB TS / DSS TS Packet Size with frame size.


Thanks.  After more googling, I was about to post that I was probably confusing two different definitions for frame.  I found this:
 
Quote:
   "Improved coding: a modern large LDPC code is concatenated with an outer BCH code to achieve quasi-error-free (QEF) reception conditions on an AWGN channel. The outer code is introduced to avoid error floors at low bit-error rates. A single forward error correction or FEC frame may have either 64,800 bits (normal) or 16,200 bits (short). If VCM or ACM is used, the broadcast can be a combination of normal and short frames.  "


which corresponds to your link above.  It's pretty much beyond my understanding, but it seems like the 188 vs 131 ?frames? I mentioned must be relative to the payload, while the frames discussed in your link and the above must be relative to the DVB structure containing that payload, particularly the FEC.  Given the above, perhaps when frame mode is enabled, it only passes the normal long frames, which explains why DVB-QPSK worked but DVB-S2-8PSK didn't work. ?

majortom

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Reply with quote  #6 
Well,  a Transport Stream, consists of demodulated Packets and the demod process has been completed at that point right?
Packets consist of a number of bytes....
the 188 vs 131 thing relates to the size of each packet within a given Transport Stream.
DVB (ETSI) does it one way (the same way as 'MPEG TS'), DSS does it their way. Simple as that.

Frame Length relates more to the bits and timing... The Transport stream isn't put back together at this point yet, as we are still inside the demod, demodulating the signal, correcting errors when we talk about Frame Length is my interpretation..

There are Short Frames and Long Frames in the DVB-S2 standard.
The devices we use for viewing FTA signals are only capable of Long Frame which is more suitable for video traffic.
The more expensive professional devices are capable of either/or.
Why? Because with video you wanna optimize the transmission for throughput, for the requirements of say HD Video. So shove as many bits as you can at once in there to reduce the amount of error correction overhead required to get the data there successfully.

With IP based solutions/data traffic however we start to be more concerned with other things such as latency, eg the amount of time it takes a packet to get from point A to Point B successfully, as it starts to be annoying for the end user if this is too long. So by slicing the frames in to smaller # of bits (short frame), we can make the transmission more granular... allowing for better control of the latency.

For example, if we are on a Voice over IP phone call, and it takes 6 seconds for my first 'hello wejones' to get to you, your probably just gonna hang up on me before the conversation even gets started. Unrealistic extreme example, but u get the point.


__________________
Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
DB8E/VHF Yagi rotor FM Bandstop ap-8700 preamp 8way split LG lcd.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html

majortom

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Reply with quote  #7 
Another way to demonstrate how latency is affected by size, compare ping...
granted with ping -s we are specifying the number of  bytes in a ping packet, not the # of bits in a demod being error corrected, but same principle applies.

as an experiment compare:
for linux:
-s <size>          use <size> as number of data bytes to be sent

ping -s 64 some_ip_addr
to
ping -s 65507 some_ip_addr

I think this would be the right syntax
/l <Size> Specifies the length, in bytes, of the Data field in the echo Request messages sent. The default is 32. The maximum Size is 65,527.
for windows:
 
ping /l 64 some_ip_addr
to
ping /l 65507 some_ip_addr

and show the results in ur next post...



__________________
Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
DB8E/VHF Yagi rotor FM Bandstop ap-8700 preamp 8way split LG lcd.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html

sat45

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Reply with quote  #8 
Some details on FrameMode option:
  • http://www.sat-digest.com/forum/viewtopic.php?t=36609
  • https://rickcaylor.websitetoolbox.com/post/tbs6983-available-7139104

  • It was an option useful only for TBS 6925 V2, with combination with NoPidFilter it could be possible to get all traffic from card, probably no matter how packetized, which could be useful for data transmissions ACM/VCM, BBFRAMES etc. However it did not worked fine, because of HW limitations of TBS 6925.

    I think it is not related to long/short FEC frames, but baseband frames (BBFRAMEs).

    Maybe crazycat can add something here.
    crazycat

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    Reply with quote  #9 
    This option only for STV09xx based devices. FrameMode=1 disable DVB-S2 packet delineator (so force raw bb frames output instead ts). Generic continous stream alway output as raw frames.
    TBS USB drivers support only TS streaming, so this option usable only with TBS PCI-E like 6925, 6983, 6903/5/8.

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    wejones

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    Reply with quote  #10 
    Thanks SAT45 and Crazycat


    Quote:
    Originally Posted by crazycat
    This option only for STV09xx based devices. FrameMode=1 disable DVB-S2 packet delineator (so force raw bb frames output instead ts).


    This explains most of my symptoms, ie:



        TBS 6983 \
        TBS 5927    STV091X based, so frame mode=1 gives bb frames instead of transport.
        Prof 7500 /


        TBS 5520SE   Si2183 based, so not affected by frame mode=1.


    However I'm still not understanding why the 3 STV091X were still able to receive DVB-S QPSK??



    wejones

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    Reply with quote  #11 
    Thanks SAT45 and Crazycat


    Quote:
    Originally Posted by crazycat
    This option only for STV09xx based devices. FrameMode=1 disable DVB-S2 packet delineator (so force raw bb frames output instead ts).


    This explains my symptoms, ie:



        TBS 6983 \
        TBS 5927    STV091X based, so frame mode=1 gives bb frames instead of transport.
        Prof 7500 /


        TBS 5520SE   Si2183 based, so not affected by frame mode=1.

    EDIT:
    I assume that the 3 STV091X were still able to receive DVB-S QPSK because this parameter only affects DVB-S2?




    crazycat

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    Reply with quote  #12 
    DVB-S, DSS transmit only TS packets.
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    Strong offset dish 0.95m on Powertech DG240 motor + ALPS BSTE8-751B Ku-Universal LNB. Variant CA-902 0.95 offset dish with 3xDreamSat DS-8 Ku-Universal LNBs (13E+4.8E+4W) + Variant CA-600 Ku-Circular LNB 36E + DiseqC 1.0. STB: GI8120 Lite. PC DVB: Omicom S2 PCI; TBS 6983 PCI; TBS QBox-CI USB(5980), 5927.
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