Jump to content


Welcome to DBSTalk


Sign In 

Create Account
Welcome to DBSTalk, like most online communities you must register to view or post in our community, but don't worry this is a simple free process that requires minimal information for you to signup. Be a part of DBSTalk by signing in or creating an account.
  • Start new topics and reply to others
  • Subscribe to topics and forums to get email updates
  • Get your own profile page and make new friends
  • Send personal messages to other members.
 
Guest Message by DevFuse

Photo

How much compression does E* use?


  • This topic is locked This topic is locked
11 replies to this topic

#1 OFFLINE   JonBlack

JonBlack

    Legend

  • Registered
  • 190 posts
Joined: Feb 24, 2005

Posted 11 September 2005 - 08:44 PM

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

...Ads Help To Support This SIte...

#2 OFFLINE   ibglowin

ibglowin

    Godfather/Supporter

  • Gold Members
  • 1,424 posts
Joined: Sep 10, 2002

Posted 12 September 2005 - 07:23 AM

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*
Mike

"I always wanted to be a scientist, and now I are one."

#3 OFFLINE   dfergie

dfergie

    Hall Of Fame

  • Registered
  • 1,166 posts
Joined: Feb 27, 2003

Posted 12 September 2005 - 08:48 AM

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*

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

#4 OFFLINE   Slordak

Slordak

    Hall Of Fame

  • Registered
  • 1,476 posts
Joined: Dec 17, 2003

Posted 12 September 2005 - 12:16 PM

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 OFFLINE   olgeezer

olgeezer

    Guest

  • Registered
  • 1,833 posts
Joined: Dec 05, 2003

Posted 12 September 2005 - 12:25 PM

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 OFFLINE   JonBlack

JonBlack

    Legend

  • Topic Starter
  • Registered
  • 190 posts
Joined: Feb 24, 2005

Posted 12 September 2005 - 01:02 PM

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.)

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 OFFLINE   Slordak

Slordak

    Hall Of Fame

  • Registered
  • 1,476 posts
Joined: Dec 17, 2003

Posted 12 September 2005 - 01:30 PM

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 OFFLINE   olgeezer

olgeezer

    Guest

  • Registered
  • 1,833 posts
Joined: Dec 05, 2003

Posted 12 September 2005 - 01:39 PM

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)?


I think they're doing about 10 SD per transponder and 3 HD

#9 OFFLINE   Roger Tee

Roger Tee

    Mentor

  • Registered
  • 49 posts
Joined: Feb 22, 2004

Posted 12 September 2005 - 04:40 PM

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 OFFLINE   Mark Holtz

Mark Holtz

    Day Sleeper

  • DBSTalk Club
  • 9,747 posts
  • LocationSacramento, CA
Joined: Mar 23, 2002

Posted 12 September 2005 - 05:32 PM

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.
:sleeping:  I am a day sleeper. I follow a European schedule.
Check out my list of links.

#11 OFFLINE   peano

peano

    Icon

  • Registered
  • 747 posts
Joined: Feb 01, 2004

Posted 12 September 2005 - 06:04 PM

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?


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 OFFLINE   Slordak

Slordak

    Hall Of Fame

  • Registered
  • 1,476 posts
Joined: Dec 17, 2003

Posted 13 September 2005 - 07:28 AM

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...




spam firewall