Satellite Buffer
- Thread starter nkeeper
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When you use E* you are not watching "live" tv. Due to the nature of the service there is a delay of several seconds. This is caused by the fact that the programming E* receives (with the exception of HDTV channels) is analog video. The video has to be converted to digital video, then compressed and multiplexed with up to a dozen other channels per transponder frequency before it can be up-linked to the satellites.
This is not unique to E* the same process applies to D* and to digital cable.
There is also a delay due to the fact that the satellites are in a geosynchronous orbit 22,00 miles up. The 44,000 mile round trip takes ~0.24 seconds at the speed of light.
So is the programming "live"? No. But it is not delayed more than is required by the processes and technologies needed to make DBS TV work.
If you use a DVR/PVR receiver there is an additional second or two delay imposed in order to allow the DVR functions to work.
This is not unique to E* the same process applies to D* and to digital cable.
There is also a delay due to the fact that the satellites are in a geosynchronous orbit 22,00 miles up. The 44,000 mile round trip takes ~0.24 seconds at the speed of light.
So is the programming "live"? No. But it is not delayed more than is required by the processes and technologies needed to make DBS TV work.
If you use a DVR/PVR receiver there is an additional second or two delay imposed in order to allow the DVR functions to work.
If you have locals via Dish and can get them OTA, you'll see how much of a delay there is.
I've seen the delay between the two..somewhere aroubnd 5-6 seconds. Cable is about 2 seconds behind.
I've seen the delay between the two..somewhere aroubnd 5-6 seconds. Cable is about 2 seconds behind.
Thanks for the info guys.
Follow up question:
I am being told that the receiver actually buffers 1-5 seconds of video before it displays it. They are talking about all regular DBS receivers (not dvr, pvr, tivo) that sit on top of our TVs. Just wanting to know if this is true and how it is being done. They said for example; the Dish 322, 111 and 301 do this.
Thanks.
Richard
Follow up question:
I am being told that the receiver actually buffers 1-5 seconds of video before it displays it. They are talking about all regular DBS receivers (not dvr, pvr, tivo) that sit on top of our TVs. Just wanting to know if this is true and how it is being done. They said for example; the Dish 322, 111 and 301 do this.
Thanks.
Richard
It just depends on how you define buffer. A buffer usually just a FIFO queue that two different devices have access to. In the case of our receivers, there would be a buffer inbetween the tuner and the decoder. As soon as the tuner tunes into the data, it has to put it somewhere. The decoder might not be immediately available to receive that data. In order for the tuner not to be blocked from tuning in additional data, it just shoves it into the buffer for the decoder to pick up a fraction of a moment later. I have no idea how big the buffer is, but I wouldn't say it's more then just a fraction of a second's worth...definitely not a 5 second buffer. I beleive stadard def channels are 6-8 mbits/sec. That means about a megabyte per second. A 5 second buffer would require 8 megs. Not a huge amount of memory these days, but none-the-less an additional cost that can be eliminated.
