Dish (and satellite in general) compression questions

[tsummerall]

Hi Folks,

I have a very specific image quality question I'll be asking in another post, but I realized I am pretty ignorant about how Dish Network transmission works and I'm hoping some kind soul will provide me an explanatory link or help me understand the following questions. This will help me diagnose problems in the future.

I have a pretty good grasp of how digital video compression works. These questions are about how it all happens across the sat-link

1. I know different channels are allotted different amounts of bandwidth by Dish. Is it also more granular than that? Does the amount of bandwidth change during different time-slots? Or even during a show providing more image quality for commercials?

2. Does reception affect quality or is it an on-or-off thing? I know what happens during heavy rain/snow events. I'm talking about general signal strength. If my antenna is poorly positioned is it possible to get a lower bandwidth signal? Or is it that if I can see a channel at all I'm getting everything there is to get in terms of data. If it varies with quality what is the best way to tell what my transmission rate is compared to the ideal for a given channel?

3. Do Dish DVRs (I have a 722k) do additional compression or do they record exactly what is coming in through the antenna? (I assume the latter.)

Any other basic facts about this stuff that every tech-savvy sat user should know?

Thanks!

 

[TheKrell]

1. Dish uses statistical multiplexing of different channels on the same transponder. So, in theory, when one channel is in need of less bandwidth in one second, it gets less bandwidth freeing up the remainder for another channel. I do not know the granularity, but I imagine it's less than a second.
2. Reception of a digital signal is pretty much all or nothing. You can see what happens when you have a marginal signal. When the error rate goes up enough that error correction can't handle it, you can get macroblocking, or frozen blocks, or (in my case) garish green blocks, or a frozen picture, or nothing (loss of signal pop-up message).
3. I believe the transport stream of demultiplexed and decrypted channels get recorded to disk as is without additional compression. The Sling Adapter does additional compression. If you have a HwS, the DishAnywhere transfer function also imposes additional compression. I think.