or Connect
AVS › AVS Forum › HDTV › HDTV Technical › Coupon Eligible Converter Box (CECB) › How many standard def channels can one TV station run?
New Posts  All Forums:Forum Nav:

How many standard def channels can one TV station run?

post #1 of 37
Thread Starter 
I've heard of a TV station somewhere (on the West Coast, I think) that is currently running TWELVE channels (with, apparently, plans to do more).

I thought you couldn't get more than 4 Standard Def channels out of one digital TV channel. Apparently that figure is far too low?

Anyone know what the limit is before the individual sub-channels are nothing but random pixels?
post #2 of 37
I don't know that a theoretical limit of the number exists. But, that's not really important. What is important is that each subchannel in addition to a main HD channel negativity affects HD image quality.
post #3 of 37
Quote:
Originally Posted by Ken H View Post

I don't know that a theoretical limit of the number exists. But, that's not really important. What is important is that each subchannel in addition to a main HD channel negativity affects HD image quality.

I can guarantee that 12 subchanels would effect SD quality too.
post #4 of 37
Quote:
Originally Posted by BCF68 View Post

I can guarantee that 12 subchanels would effect SD quality too.

A few years ago during March Madness, before CBS could do 4 HD feeds at once, the local affiliate ran 4 SD basketball games at one time. It wasn't pretty.
post #5 of 37
Thread Starter 
Quote:
Originally Posted by Ken H View Post

I don't know that a theoretical limit of the number exists. But, that's not really important. What is important is that each subchannel in addition to a main HD channel negativity affects HD image quality.

The one doing 12 isn't even doing any HD, from what I understand. ALL its channels are SD.
post #6 of 37
Quote:
Originally Posted by gastrof View Post

The one doing 12 isn't even doing any HD, from what I understand. ALL its channels are SD.

Which we're not concerned with here, as this is an HD forum.
post #7 of 37
Quote:
Originally Posted by Ken H View Post

Which we're not concerned with here, as this is an HD forum.

So are you saying that we are not allowed to discuss the matter?
post #8 of 37
Quote:
Originally Posted by Ken H View Post

Which we're not concerned with here, as this is an HD forum.

WOW!

Ken, you are a great mod, but that seems uncalled for. Just in the last few weeks there have been threads about non-hd set top boxes, antenna questions, etc. that really have NOTHING to do with HD, although they do have everything to do with DTV, as does this thread. There was even a thread about Dick's Sporting Goods and Winegard antennas.

This thread is very related to DTV, but because you are a proponenet of single channel full bandwidth HD (no subchannels), you cut the post down.

Why? What about sub-channels that are not and will not be HD? Are they to be thrown away? RTN shows classic TV shows, shot in 4/3 SD. Why should this channel not be SD DTV? I would be happy if I could see sub channels carrying old movies in 480p widescreen. DVD quality would be acceptable to me for older movies and the bandwidth of 480p widescreen may allow for 2 very good looking subchannels.

I wish that all TV was single channel HD also, but I am positive that it will never happen in my small DMA (Green Bay, WI). Although I must say that we do quite well...CBS, Fox, NBC, MyN and CW are all single channel HD at this point, with only ABC and PBS being multi-channel broadcasts (each have a pair of SD subchannels to go with their HD signal).

The fact is, in this area, we will not see a lot of new startup stations erecting new towers. The money just will not be there. In my area, the 5 single HD channels will most likely add an SD subchannel or two as new ones come along. We do not yet have NBC Universal Sports, This TV or Untamed Sports in this DMA (although the Wausau, WI DMA does). There will be others that come along in the following years.

Why is this thread not relevant to HDTV Technical, but STB threads are?

Bill
post #9 of 37
The rule as I understand it is that these things are fair game in the Local HDTV forum, but in HDTV Technical it stays focused on HD. Any SD stuff goes in the CECB forum. I assume Ken will correct me if I'm wrong on that.

- Trip
post #10 of 37
Quote:
Originally Posted by TV Trey View Post

So are you saying that we are not allowed to discuss the matter?

?

It should be obvious that we are discussing the matter, right here and now. My point is, HDTV is the focal point of HDTV Technical.

Due to HDTV being part of Digital TV, we allow discussion of all Digital TV reception issues in HDTV Technical.

We also have a forum for non-HD Digital TV issues, the CECB Forum. It contains non-HD box topics and other non-HD related topics including subchannel programming. This topic has been moved there.

At some point the CECB forum title will be changed to something more generic, that will accommodate all non-HD issues, with the exception of Digital TV reception, which will remain here in HDTV Technical.
post #11 of 37
Quote:
Originally Posted by gastrof View Post

The one doing 12 isn't even doing any HD, from what I understand. ALL its channels are SD.

Ok I'll actually answer the question. There is limit to what makes a GOOD picture regardless of how many subchannels you could technically put there. HD, SD doesn't matter. SD just allows for more channels to be put there before you get a crappy picture. With HD it's basically ONE, and preferably with zero subchannels especially with 1080i. With 480i you'd want close to 6 Mbps for a great picture(as SD is concerned ) which means maybe 3 subchannels at most. For a decent looking picure you go say 4 Mbps which means maybe 4 subchannels. You get much below 4 Mbps then things start looking like a show you recorded on a VHS tape or worse. Some of those 12 subchannels aren't even 1 Mbps. Which would make them look close to Youtube quality if you get my drift.

If stations would start using the newly approved MPEG-4 compression for ATSC, which of course would require TV sets and/or converters than have MPEG-4 tuners in them( NONE do right now ) then you could have a 720p/1080i main channel and a few SD subchannels and still have a good HD pciture. Or you could have 2 HD channels and that's it. Or one 1080p channel( with maybe 1 SD subchannel ). Odds are though brocasters would try to overstuff subchannels like they do now.
post #12 of 37
What does this thread have to do with CECBs?

Now, if they could just find another place for the ridiculous fan-chat, rather than on the ostensibly HDTV Programming topic. Nobody minds an occasional programming opinion, but that got out of hand a long time ago.

The HDTV Programming thread is almost useless for discussing HD aspects of shows. Almost all prime-time programs on the networks are HD. Plot and play-by-play chat needs to go someplace else. Fer crissakes, make a Progam/Fan Chat forum and have the amateur directors, writers, and critics go there.

Sorry to sound like a whining, broken record.
post #13 of 37
Quote:
Originally Posted by willscary View Post

Although I must say that we do quite well...CBS, Fox, NBC, MyN and CW are all single channel HD at this point, with only ABC and PBS being multi-channel broadcasts (each have a pair of SD subchannels to go with their HD signal).

Ah, but when Fox network programming is being aired, you really do have a SD sub-channel. Huh? While your station, including my local Fox aflliate, may not be actually putting out a tunable sub-channel, Fox allocates space for one. They limit the HD to a max of 15 Mbps.

So, even if your station doesn't do SD, it is crippled so that it can.
post #14 of 37
Quote:
Originally Posted by hphase View Post

What does this thread have to do with CECBs?

I hope you realize it was the MOD that moved this thread here. So are you questioning his decisions?
post #15 of 37
Variation on the question: let's say that bit allocation and picture quality aren't issues (for example, all the channels are just bulletin boards and the video has slight updates every few seconds, maybe even without audio); how many channels does the ATSC spec permit per station?
post #16 of 37
IIRC 99 DTV and audio-only, up to 999 for other purposes. Hopefully a broadcast engineer who knows for sure will reply.

Interestingly enough, it appears to have nothing to do with the frequency it is transmitted on. Where I am, 19.1 and 64.2 are transmitted on one frequency. And 19.2 and 64.1 are transmitted on another.
post #17 of 37
Quote:
Originally Posted by dattier View Post

Variation on the question: let's say that bit allocation and picture quality aren't issues (for example, all the channels are just bulletin boards and the video has slight updates every few seconds, maybe even without audio); how many channels does the ATSC spec permit per station?

I think the limit is 65535. Why? Because I believe the tables are limited to 0xFFFF. Maybe even one less, since the null packets are one of them.

This is a WAG on my part.
post #18 of 37
Quote:
Originally Posted by Colm View Post

IIRC 99 DTV and audio-only, up to 999 for other purposes. Hopefully a broadcast engineer who knows for sure will reply.

Like I said, mine was a WAG.
post #19 of 37
IIRC the major and minor channel numbers are 10 bits. That would be 1024 possible values. My WAG is that the committee decided on the range of values they wanted, then used the minimum number of bits necessary to represent it.
post #20 of 37
PIDs are 13 bits (max value 0x1fff), for a total of 8192 possible tables or streams inside the TS.


Major and minor channels in a VCT are 10 bits each. On terrestrial broadcasts, the major channel must be 1-99. The minor channel must be 1-99 on digital TV or audio, but can go up to 999 for data services.

In a CVCT, if the top 6 bits of the major channel are set (decimal 1008 or higher), it is considered a one-part virtual channel, like a cable channel. This is often not implemented correctly in software and firmware dealing with clear QAM. Otherwise, both the major and minor must be below decimal 1000.
post #21 of 37
Quote:
Originally Posted by coyoteaz View Post

PIDs are 13 bits (max value 0x1fff), for a total of 8192 possible tables or streams inside the TS.

I knew something didn't look right about the 0xffff that I posted. I couldn't check because the computer I use for that was undergoing troubleshooting to track down an errant runaway hardware interrupt. Turns out my new graphics card, after being used for a short period of time, just starts interrupting for no reason at
all. It will stop doing it when the program calling it stops (graphics accelleration). Reboot and it is OK, until whatever trips it starts it doing it all again. In any event, I just couldn't remember for sure. Thanks for the update.
post #22 of 37
Thanks to Colm and CoyoteAZ for answering. MrVideo, thanks for contributing, and you know I'm still grateful for help in the past.
post #23 of 37
Quote:
Originally Posted by BCF68 View Post

I hope you realize it was the MOD that moved this thread here. So are you questioning his decisions?

Yup!
post #24 of 37
Quote:
Originally Posted by mrvideo View Post

...So, even if your [fox] station doesn't do SD, it is crippled so that it can.

It is also limited in that only a set amount can be stolen from the HD channel to do subs, which is good.

Commercial stations exist to make money. If doing subs will make them more money, most will eventually do subs.
post #25 of 37
OTA broadcasts allow 19.4 mbps (million bits per second). Lets assume that we are only talking about a transmission with no HD channels. I believe I once read that Dish network broadcasts their satellite SD channels at 2.5 mbps. That would allow about 8 SD channels of the Dish Network quality. If the channels were broadcast in MPEG4 instead of MPEG2 you could maybe double that to 16 SD channels. If you were willing to decrease the channel quality further you might even get 20 SD channels on a OTA digital channel. This would be pushing it to the extreme, but maybe possible.

Rick R
post #26 of 37
Quote:
Originally Posted by Rick_R View Post

OTA broadcasts allow 19.4 mbps (million bits per second). Lets assume that we are only talking about a transmission with no HD channels. I believe I once read that Dish network broadcasts their satellite SD channels at 2.5 mbps. That would allow about 8 SD channels of the Dish Network quality. If the channels were broadcast in MPEG4 instead of MPEG2 you could maybe double that to 16 SD channels. If you were willing to decrease the channel quality further you might even get 20 SD channels on a OTA digital channel. This would be pushing it to the extreme, but maybe possible.

Rick R

You're not accounting for sound. Each channel would be using at minimum 128 kbps for sound. Closer to 192 kbps is more realistic. So really at 2.5 Mbps you could only fit 7 total channels.

Also look at it this was cable uses mpeg-2 just like dvd. Not sure about Dish. DVD first of all is 480p unlike SD cable and satelite which are 480i. DVD has a bitrate of 8 Mbps. Even if one wants to argue that 480i only needs half the bandwidth of 480p then that's still 4 Mbps. So if you want DVD quality via OTA ( or cable/sat for that matter ) station would need to be broadcasting in 480p at 8 Mbps which of course is NOT going to happen. So 8 subchannels would look not much better than VHS quality.

Ideally is a station was broadcasting nothing but SD content I wouldn't want to see more than 4 total channels on it.
post #27 of 37
Looks like the station with 12 channels is KAXT-LD in the San Francisco bay area.
42.1 01-01 CoolTV 480i 3.7Mbps DD1.0 112kbps
42.2 01-02 QH-TV 480i 1.8Mbps DD1.0 96kbps
42.3 01-03 TF-TV 480i 0.9Mbps DD1.0 64kbps
42.4 01-04 BahiaTV 480i 1.65Mbps DD2.0 96kbps
42.5 01-05 DiyaTV 480i 0.95Mbps DD1.0 80kbps
42.6 01-06 Colours 480i 1.2Mbps DD1.0 80kbps
42.7 01-07 Family 480i 1.55Mbps DD1.0 96kbps
42.8 01-08 i2TV 480i 0.7Mbps DD1.0 64kbps
42.9 01-09 Corner 480i 1.1Mbps DD1.0 64kbps
42.10 01-10 Coastal 480i 1.45MbpsDD1.0 96kbps
42.11 01-11 Jewelry 480i 1.35MbpsDD1.0 64kbps
42.12 01-12 Peanut 480i 0.7Mbps DD1.0 64kbps
42.13 01-13 QH Radi DD1.0 64kbps
42.14 01-14 C-Music DD1.0 96kbps
42.15 01-15 La-Voz DD1.0 64kbps

They could fit about 25 channels with 0.7Mbps video and 64kbps audio.
post #28 of 37
Quote:
Originally Posted by jeff2631 View Post

Looks like the station with 12 channels is KAXT-LD in the San Francisco bay area.
42.1 01-01 CoolTV 480i 3.7Mbps DD1.0 112kbps
42.2 01-02 QH-TV 480i 1.8Mbps DD1.0 96kbps
42.3 01-03 TF-TV 480i 0.9Mbps DD1.0 64kbps
42.4 01-04 BahiaTV 480i 1.65Mbps DD2.0 96kbps
42.5 01-05 DiyaTV 480i 0.95Mbps DD1.0 80kbps
42.6 01-06 Colours 480i 1.2Mbps DD1.0 80kbps
42.7 01-07 Family 480i 1.55Mbps DD1.0 96kbps
42.8 01-08 i2TV 480i 0.7Mbps DD1.0 64kbps
42.9 01-09 Corner 480i 1.1Mbps DD1.0 64kbps
42.10 01-10 Coastal 480i 1.45MbpsDD1.0 96kbps
42.11 01-11 Jewelry 480i 1.35MbpsDD1.0 64kbps
42.12 01-12 Peanut 480i 0.7Mbps DD1.0 64kbps
42.13 01-13 QH Radi DD1.0 64kbps
42.14 01-14 C-Music DD1.0 96kbps
42.15 01-15 La-Voz DD1.0 64kbps

They could fit about 25 channels with 0.7Mbps video and 64kbps audio.

See this thread.

http://www.avsforum.com/avs-vb/showthread.php?t=1175674

http://www.w6rz.net/kaxt.htm

http://www.w6rz.net/kaxt_090309.ts

Ron
post #29 of 37
Quote:
Originally Posted by gastrof View Post

The one doing 12 isn't even doing any HD, from what I understand. ALL its channels are SD.

They shouldn't even be called SD unless that S stands for an expletive rather than Standard.
post #30 of 37
Quote:
Originally Posted by jeff2631 View Post

Looks like the station with 12 channels is KAXT-LD in the San Francisco bay area.
42.1 01-01 CoolTV 480i 3.7Mbps DD1.0 112kbps
42.2 01-02 QH-TV 480i 1.8Mbps DD1.0 96kbps
42.3 01-03 TF-TV 480i 0.9Mbps DD1.0 64kbps
42.4 01-04 BahiaTV 480i 1.65Mbps DD2.0 96kbps
42.5 01-05 DiyaTV 480i 0.95Mbps DD1.0 80kbps
42.6 01-06 Colours 480i 1.2Mbps DD1.0 80kbps
42.7 01-07 Family 480i 1.55Mbps DD1.0 96kbps
42.8 01-08 i2TV 480i 0.7Mbps DD1.0 64kbps
42.9 01-09 Corner 480i 1.1Mbps DD1.0 64kbps
42.10 01-10 Coastal 480i 1.45MbpsDD1.0 96kbps
42.11 01-11 Jewelry 480i 1.35MbpsDD1.0 64kbps
42.12 01-12 Peanut 480i 0.7Mbps DD1.0 64kbps
42.13 01-13 QH Radi DD1.0 64kbps
42.14 01-14 C-Music DD1.0 96kbps
42.15 01-15 La-Voz DD1.0 64kbps

They could fit about 25 channels with 0.7Mbps video and 64kbps audio.

Great and now you can watch the equivilent of youtube "quality" video on your 50 inch HDTV. Even on an old 13" tube Tv those stations would look like crap.
New Posts  All Forums:Forum Nav:
  Return Home
AVS › AVS Forum › HDTV › HDTV Technical › Coupon Eligible Converter Box (CECB) › How many standard def channels can one TV station run?