[opendtv] Re: News; Dish to Expand HD Roster, Offer 1080p Movies

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Sat, 2 Aug 2008 19:06:24 -0400

Bert,
My own station broadcasts one 720p and three 480i streams in our multicast. We chose 720p because at the lower bitrate required to squeeze in three SD multiplexes, there was much more macroblocking using 1080i vs. 720p. This is using Tandberg encoders.
We also use statistical multiplexing to allocate bits to all four services, so there are times when the HD is running at 7 Mbps, and others when it is running at 16 Mbps (for the video).
The only numbers I saw were given for Blu-Ray discs. I will guarantee you that Dish is not using anything close to 24 Mbps for any of their movie channels. I would be willing to wager that the average bit rate is under 10 Mbps per stream, and from some demos I've seen (to be taken with a very large grain of salt,) could even be averaging under 5 Mbps using stat muxing .
Yes, ATSC may be able to broadcast 1080p24, but using MPEG-2 vs. MPEG-4, the latter will look much better at identical bitrates or look the same at lower bitrates. 

John
----- Original Message ----- From: "Albert Manfredi" <albert.e.manfredi@xxxxxxxxxx> 
To: <opendtv@xxxxxxxxxxxxx>
Sent: Saturday, August 02, 2008 5:57 PM
Subject: [opendtv] Re: News; Dish to Expand HD Roster, Offer 1080p Movies
They gave the numbers in the article, John, and there's nothing particularly impressive about any of it.
First of all, while it's true that I can see blocking artifacts when fast motion is in the picture, I'll say again that WETA-DT transmits one 1080i and three 480i streams in their multiplex. So somehow, they HAVE to be using far less than the 16-24 Mb/s these BD H.264 files transmit. I'd estimate conservatively that the avg bit rate can't be more than 12 Mb/s, and that assumes the SD streams use LESS than 2.5 Mb/s average each. 



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