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How much compression does E* use?

Discussion in 'General DISH™ Discussion' started by JonBlack, Sep 11, 2005.

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  1. JonBlack

    JonBlack Legend

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    Feb 24, 2005
    I've read some stuff on this and I'm not for sure at this point what is true and what isn't true. With these numbers for comparision, DVD video is roughly 6Mbps and that HDTV is roughly 19 Mbps in bitrate, I'm just trying to get some rough estimates on how much or little compession that E* uses.

    1) Does E* use a shifting compression scheme? e.g. high action broadcasts such as sports will get more banwidth, then reduce for less movement such as a news broadcast?

    2) Does E* broadcast SD channels in 480x480 resolution?

    3) What is the bitrate on the premium channels, such as HBO, PPV, etc.?

    4) What is the bitrate on the standard national channels, such as USA, ESPN, etc.?

    5) What is the bitrate on the local channels, SD of course?

    6) What is the bitrate on the HD channels?

    7) Are E*'s HD channels broadcasted in 1024x1280 or 1024x1920?

    Thanks,
    JB
     
  2. ibglowin

    ibglowin Godfather/Supporter DBSTalk Gold Club

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    Not as much as D* thats for sure. I just looked at a friends JVC 60" DILA. That thing should have an awesome PQ. He has D* and the PQ just sucked big time. Was grainey and pixelated at the slightest movement.

    I have E* and a Sony 60" WEGA RPTV. The HD PQ is no comparsison IMHO on E* vs D*
     
  3. dfergie

    dfergie Hall Of Fame

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    I have both... what ibglowin says... :)
     
  4. Slordak

    Slordak Hall Of Fame

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    Dec 17, 2003
    Actually I have a somewhat-related question. Does anyone know how much additional bandwidth Dish Network was using to send its channels using both of its encryption schemes simultaneously? And now that Dish is retiring the original Nagravision stream on most channels, does this free up additional bandwidth for new channels or for improving the quality of existing channels?
     
  5. olgeezer

    olgeezer Guest

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    Dec 5, 2003
    I'll guess:
    1. Yes
    2. Used too, but think they are now 640x480
    3-6. Because one is yes bitrate is variable (ie while sports may run 19.4Mbs, movies may run as little as 6Mbs.)
    7. They are broadcast at 1920X1080 or 1280x720 depending on the original broadcast (ie. ESPN runs 1280X720p, CBS 1920x1080i.)
     
  6. JonBlack

    JonBlack Legend

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    Feb 24, 2005
    Thanks for the answers so far folks. It's a little more clearer to me.

    I guess I should have asked questions 3-6 like this.

    1) How much bandwidth/bitrate is available per transponder?

    2) Then how many of each type of channel is usually squeezed into a transponder (premium, standard nationals, locals, hdtv)?
     
  7. Slordak

    Slordak Hall Of Fame

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    I believe each transponder has 24 Mhz of frequency bandwidth, with something slightly less than this as the "usable bandwidth". The amount of data this translates to depends on the encoding scheme and the amount of error correction. I believe Dish is using a symbol rate of 20000 for standard channels, which is something like 40 Mbps of data in QPSK minus the amount used for error correction.
     
  8. olgeezer

    olgeezer Guest

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    I think they're doing about 10 SD per transponder and 3 HD
     
  9. Roger Tee

    Roger Tee Mentor

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    Feb 22, 2004
    Let me whack in here:

    Last time I checked Standard channels were 544 by 480 and premiums (HBO etc.) were 640 by 480.

    Bitrate is variable and dynamic with the statistical multiplexers, Each transponders channels change bitrate on the fly giving more to fast action and less to things such as slow moving video. Pay channels will always get preference over non-pay channels so that if there isn't enough bandwidth on the transponder the premiums get preference.

    Many channels seem to run around 1 Gigabyte per hour disk space usage. Premiums run higher. I'm basing this on several things including time left on my 501s and percentage left on my Dishplayers... Why the 721 is onlya 90hour machine I do not know as I believe it has a 120Gb drive unless they have reserved a lot of space for dish uses beyond the dual buffers requirement.

    Edit: almost forgot DVDs can run from 1150Kb to approix 10Mb bitrate. The 1150Kb being the standard for the low res 352 by 240 setting.

    DVD specs generally are 352 by 240, or 352 by 480 or 704 by 480 or 720 by 480 here in NTSC land.
     
  10. Mark Holtz

    Mark Holtz Day Sleeper DBSTalk Club

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    It's really hard to compare DVD with DBS because you are talking about two different creatures even though both essentially use the MPEG2 compression format. Both formats have limitations. For DVD, the issue is disc capacity, while, for DBS, the main issues are time and transponder capacity.

    DBS compression is done in real time. For a non-premium channel, you have video plus one or two audio streams. The audio is usually a stereo audio feed. The DBS companies have to compress the signal as it comes down, and do not have the luxury of time.

    In contrast, the folks who make the DVDs have the luxury of time, but not disc space. Often, they do the scanning of the images, then leave the computers "sitting there" for several days crunching down the data in order to come up with a better picture. For a major feature DVD, you can have several audio tracks at once. I'm looking at the technical specs for Toy Story-10th Anniversary Edition, and that features a Dolby 5.1 Audio, DTS 5.1 Audio, Spanish and French Language, and a commentary track. Dolby 5.1 audio takes up more bandwidth than Stereo audio, and DTS even more so.

    I believe that MPEG also employs a lossy compression scheme similar to the JPEG pictures. When you are saving a JPEG image, you can increase the quality and make the picture sharper, but the file size is bigger. Likewise, by decreasing the quality and making the picture softer, the file size is smaller.

    Unfortunately, both DirecTV and Dish Network's main sats are at capacity. A single transponder usually holds about 8-12 stndard definition channels, and they can really push the compression on the local channels. Such is life.
     
  11. peano

    peano Icon

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    Feb 1, 2004
    There is only one video stream being sent with two sets of keys for the N1 and N2 encryption schemes on channels that have not switched over to N2.
     
  12. Slordak

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    Dec 17, 2003
    Oh. So no real bandwidth savings there, huh, other than some extremely small overhead reduction in the commands/encryption keys. Ahh well, thought it was at least worth asking about. Guess Dish is still short on bandwidth at its core orbital locations...
     
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