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DIRECTV Satellite Discussion D-14 @99W

Discussion in 'DIRECTV General Discussion' started by Sixto, Jun 17, 2010.

  1. RAD

    RAD Well-Known Member

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    Doesn't Dish using something called 8PSK Turbo to squeeze a bit more bandwidth on the MPEG4 service? http://www.broadcom.com/press/release.php?id=473736
     
  2. HoTat2

    HoTat2 Hall Of Fame

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    I know they use an "FEC Turbo" for the Viterbi convolution coding on their DVB-S/MPEG-2 SD feeds (which are only on the WA).

    But I'm not aware of a Turbo variety for the FEC used on their 8-PSK feeds since those are sent in the DVB-S2 format which use a type of "Low Density Parity Check" (LDPC) inner coding and a "Bose-Chaudhuri-Hocquenghem" (BCH) outer coding for FEC.
     
  3. cypherx

    cypherx Hall Of Fame

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    I thought Dish could put more HD per tp (like 8 to 10) due to a few different things.
    -8QPSK with TURBO FEC
    -Ku band allows higher order modulation and lower FEC = better throughput for data
    -Higher compression (1440x1080i in some cases). Fine for the "talking heads", Shopping, Government and Religious networks. But there have been complaints when used on more popular networks.

    To compare at most DirectTV put 6 HD and 1 MPEG4 SD on a single Ka transponder. I've seen as many as 10 HD or 24 SD on a Dish Network transponder.





    Sent from my iPhone using DBSTalk
     
  4. P Smith

    P Smith Mr. FixAnything

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    NIT posted, so all the parameters well known for all DTV/dish sats/tpns - see Gary Toma's and James Long's threads
     
  5. James Long

    James Long Ready for Uplink! Staff Member Super Moderator DBSTalk Club

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    As a quick comment:
    DISH uses symbol rate 21500 2/3 FEC 8PSK for most of the transponders used for HD. They also have HD on 21500 3/4 FEC 8PSK transponders and 22500 5/6 FEC "TURBO" transponders ("TURBO" is only on the satellite at 77).
    (Data rate of 39.628Mbps to 44.581Mbps on 8PSK and 34.559Mbps on "TURBO" if the math is correct.)

    Most transponders used for SD only (primarily western arc) are symbol rate 20000 7/8 FEC QPSK ... but there are spotbeams using 5/6 FEC or 1/2 FEC (symbol rate 20000 QPSK).
    (Data rate of 32.255Mbps or less if the math is correct.)

    The 10 HD transponder (one per arc) is 10 PPV channels ... I don't believe anyone has complained. "8" for the RSNs (remembering there is a 9th low bandwidth slate channel hidden on those transponders) and 9 for other channels is most common on DISH.

    I have not audited SD but I'd be surprised to see 24 unique feeds on a QPSK transponder ... the last time I checked 13 was max. On 8PSK there could easily be more than 24 unique SD feeds. (Feeds mirrored on multiple channels make counting more interesting - requiring an audit to figure out which channel numbers are sharing the same feed.)
     
  6. harsh

    harsh Beware the Attack Basset

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    I suspect what you refer to as 4PSK modulation is more commonly known as QPSK: Quadrature Phase Shift Keying.

    Gotta keep the jargon consistent.
     
  7. JosephB

    JosephB Icon

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    That sounds significant, but given the way modern video codecs work, it's probably not that big of a difference on bitrate.
     
  8. cypherx

    cypherx Hall Of Fame

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    Well it's even awhile since I looked but I did see 20-22 SD on one dish tp before. The difference was its mpeg4. DirecTV's SD on 101 is so utterly bit starved at mpeg2, that's why I'd be glad even for crap channels to make the move to HD if there's room, just to make it easier on the eyes.

    For dish, I'm in an Eastern Arc market. My tree line blocks some of eastern arc so I went with DirecTV, and I'm happy with them now. I just wish their SD wasn't so bit starved. My cable provider also uses MPEG2 for SD (and everything really), but sometimes I can't tell their SD is less than 720p. They only put 10 feeds in one 38.8mbps QAM channel.
     
  9. studechip

    studechip Godfather

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    What do movie theaters have to do with televisions?
     
  10. slice1900

    slice1900 Well-Known Member

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    Digital projection equipment already crops at the top or sides as needed, because films are produced in multiple aspect ratios, they'll do it the same way for broadcast.
     
  11. harsh

    harsh Beware the Attack Basset

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    Because movie theaters offer 4K content now, they establish what it means to be 4K.
     
  12. HoTat2

    HoTat2 Hall Of Fame

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    Yep;

    "QPSK" is what I meant by "4-PSK;"

    Sorry for any confusion ...
     
  13. HoTat2

    HoTat2 Hall Of Fame

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    So then DISH actually does not use DVB-S2 for their MPEG-4 HD and SD feeds?

    Only the first generation DVB-S or DVB-S with FEC Turbo (on the QuetzSat 1 satellite at 77W)?
     
  14. studechip

    studechip Godfather

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    Do movie theaters claim hd content now? Why do you think they will claim 4k in the future? Meaningless.
     
  15. HoTat2

    HoTat2 Hall Of Fame

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    For DIRECTV USA the numbers appear to be about 20 MegaSymbols/s (or 20 Megabaud) at a code rate of 6/7 for SD Ku channels which all use QPSK modulation. And 30 MS/s (30MB) at a code rate of 2/3 or 3/4 for the MPEG-4 HD and SD channels on Ka band which use QPSK or 8-PSK modulation (used on some spotbeams).

    Note: The Spanish HD feeds on 119 Ku tp. 24 use 20 MS/s with 8-PSK modulation to compensate for the lower SR limitation of the smaller 24 MHz bandwidth transponder.
     
  16. James Long

    James Long Ready for Uplink! Staff Member Super Moderator DBSTalk Club

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    If I read the data correctly, yes on both counts. The bit that normally denotes DVB-S2 is not set in the captured NIT.
     
  17. Mike Bertelson

    Mike Bertelson 6EQUJ5 WOW! Staff Member Super Moderator DBSTalk Club

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    I've moved a bunch of posts to the 4k discussion.

    :backtotop:

    Mike
     
  18. Ed Campbell

    Ed Campbell Hall Of Fame

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    We seem to be


    Cripes. Time for me to show up here to keep up to date, every day.

    Too many interesting topics online. :)


    Sent from my iPad using DBSTalk
     
  19. P Smith

    P Smith Mr. FixAnything

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    checking transponders by some advanced DVB-S2 cards (TBS 6920/5920) and found no DVB-S2 using there
     
  20. HoTat2

    HoTat2 Hall Of Fame

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    I see, but it's somewhat confusing though;

    When the original DVB-S standard was created in 1994, it was only to be used with MPEG-2 and a modulation level no greater than QPSK for DTH satellite services. Professional applications like DSNG could use MPEG-2 with 8-PSK or QAM-16.

    I can't find any official documentation from the ETSI of a modification of the DVB-S standard for MPEG-4 with 8-PSK for professional much less DTH services like DISH is apparently using.
     

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