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ATSC bandwith formula or table

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Old 01-09-2019, 09:49 AM   #1  
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Default ATSC bandwith formula or table

What is the formula or table for determining the allowable number of sub channels on an ATSC carrier? A 1080P and four 480P sub channels isn't uncommon but one DC area station had a 480P main and at least nine additional sub channels. There has to be a hard limit but how does one know what the mix can be? Is it as simple as a bandwidth value assigned to each channel resolution and the total must be less than the carrier allotment?

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George
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Old 01-09-2019, 06:56 PM   #2  
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As far as I know there is not any maximum numbers of sub channels the total bandwidth is just split as needed. These days most stations don't allocate a fixed amount to each sub channel, but rather they will dynamically allocate with usually the HD channel having priority.
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Old 01-09-2019, 09:28 PM   #3  
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This may help, but brew up some coffee it can get quite boring.

Code:
https://www.atsc.org/standard/a902013-atsc-data-broadcast-standard/
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Old 01-10-2019, 06:07 AM   #4  
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Quote:
There has to be a hard limit but how does one know what the mix can be?
There is no "hard" limit on the number of subs a channel can carry.

However, there is a practical limit in that it depends on how bad a broadcaster will allow their content to appear to the viewer. One can only slice up the 19.38 Mbs so many times until the content looks like youtube over dialup might. Out in LA, there are a several stations that carry more than 10 subs. In SF, one station has 16 subs.

Stations with state of the art variable bit rate encoders can set them up to prioritize content on certain subs as they deem desirable. The machine then dynamically analyzes the content (on the fly) of all the subs and encodes them to maximize quality on all of them, according to the prioritization programmed into the setup. Older encoders require the operator to set up a static allocation for each sub and then the machine just compresses the content to fit into the available allocation.
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Old 01-10-2019, 02:52 PM   #5  
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Default The "Big-Screen" Effect

I was trying to help someone who bought a new big screen TV. His wife wasn't happy with the OTA shopping networks. I explained to him that a big screen magnifies any imperfections in a signal, which I call the "Big-Screen Effect." There wasn't anything wrong with his new TV, the fault was with the poor quality transmitted signal.

In my area, WPXV ION has 6 sub channels.

https://www.rabbitears.info/market.p...&callsign=WPXV

OTA QVC, which is compressed 480i, looks pretty bad; not even as good as analog. This is a section of the lower left corner of my 32" Sony:



For comparison, this is 1080i on cable:



CBS sports OTA looks really good:



I was looking for another way to combine the signals from two antennas aimed in different directions. I was happy for many years watching analog TV, so I tried using the CH3 analog output from a converter box. It's not HD, but it is quite acceptable at normal viewing distance, and certainly better than compressed 480i digital.



The signals from both antennas can be combined in one coax for distribution using a HLSJ, which is what I did for the above comparison. All I had to do was switch from 3.1 to 3 with the TV remote control. Details upon request.

For HD from the second antenna with only one TV, use the HDMI output from the tuner and connect it to the TV HDMI input.

If you want HD from the second antenna with more than one TV, it gets complicated.

Last edited by rabbit73; 01-11-2019 at 08:54 AM..
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