Why HD distribution over DVB-T is not widely adopted - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 9 Old 04-07-2013, 03:12 AM - Thread Starter
Newbie
 
nicko82's Avatar
 
Join Date: Feb 2011
Location: Cyprus
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Im currently designing a large scale digital signage system and I was looking to reduce some costs. So I was thinking why not use HD over coax for live TV feed from satellite. The I thought, why don't we do this for home HD distribution and used expensive HDMI matrices over UTP like Crestron DM, HDbase-T etc?
DVB-T standard uses mpeg2 encoding which is capable of up to 1080p(25 I think, not 60). So why is it not widely adopted? I'm not talking about OTA, but about multi display distribution from sources such as satellite or PC.

One answer to my question is of course DHCP. One could not distribute a Bluray like that due to content protection. But what if you don't care/buy Bluray discs and only want the distribution for other sources?
Is it a marketing matter? Or is it a matter of the hardware being more expensive?
I don't get it...

Thoughts?
nicko82 is offline  
Sponsored Links
Advertisement
 
post #2 of 9 Old 04-07-2013, 03:39 AM
AVS Special Member
 
sneals2000's Avatar
 
Join Date: May 2003
Location: UK
Posts: 7,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Liked: 43
DVB-T is in use for large-scale distribution in some areas. News broadcasters, like the BBC, often have internal DVB-T "ring mains" which allow journalists to watch incoming feeds, news channels etc. at their desk. Previously these would have used conventional analogue composite modulated sources.

The costs of encoding/modulation/distribution are not insignificant, but if you need to install a couple of hundred receivers, the benefits of being able to buy off-the-shelf TVs with DVB-T decoders/demodulators in them offset this.

IPTV is also being used for this purpose - but for large-scale installs, DVB-T has advantages. (Small DVB-T LCD TVs are now very low cost items)

Domestic DVB-T modulators are reasonably widely available - to allow local AV sources to be added to an antenna-fed RF distribution system. However most of them only accept composite analogue SD sources (which they encode to 576/50i MPEG2) However there are 1080/50i models I believe - and some PC-based solutions.

(Though as this is a US-centric forum DVB-T may be of less interest to many here. The question has popped up on multiple occasions wrt to ATSC 8VSB and ATSC QAM encoding though)
sneals2000 is offline  
post #3 of 9 Old 04-07-2013, 07:07 AM
AVS Special Member
 
kenglish's Avatar
 
Join Date: Jan 2000
Location: Salt Lake City, UT, USA
Posts: 5,390
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 31
Right now, we are using a Trans-modulator to take a couple of satellite bouquets and change them to 256-QAM for distribution to our house MATV, for monitoring satellite feeds of LDS (Church) Conference.
It works, but has been a PITA with some older sets, which just don't like the QAM channels.
I'm looking around the facility for some very new sets that might also decode MPEG-4 HD.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
kenglish is offline  
post #4 of 9 Old 04-07-2013, 07:42 AM - Thread Starter
Newbie
 
nicko82's Avatar
 
Join Date: Feb 2011
Location: Cyprus
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Ok so you guys are saying that DVB-T HD modulators are quite popular (at your locations perhaps).
Then why are HDMI-UTP distribution matrices and HDbaseT are becoming more and more popular? Whats the point apart from handling DHCP? With these you even need a different remote or control system to switch between sources.
nicko82 is offline  
post #5 of 9 Old 04-07-2013, 03:31 PM
AVS Special Member
 
sneals2000's Avatar
 
Join Date: May 2003
Location: UK
Posts: 7,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Liked: 43
Quote:
Originally Posted by nicko82 View Post

Ok so you guys are saying that DVB-T HD modulators are quite popular (at your locations perhaps).
No - I didn't mention HD - and stated that they were popular for particular applications. The application I have seen first hand was where >100 channels of SD content needed to be delivered to hundreds of seats in an office (i.e. a large TV and Radio Newsroom). RF ring main with commodity, low-cost, TVs is still the neatest way to do this - and DVB-T (or -C) is better than PAL/NTSC these days.

(In the UK DVB-T is SD-only, albeit 16:9 SD. HD uses DVB-T2)
Quote:
Then why are HDMI-UTP distribution matrices and HDbaseT are becoming more and more popular? Whats the point apart from handling DHCP? With these you even need a different remote or control system to switch between sources.
If you only need to route a smaller number of sources / destinations then the economics of modulation may not make sense?
sneals2000 is offline  
post #6 of 9 Old 04-08-2013, 07:09 AM
AVS Special Member
 
kenglish's Avatar
 
Join Date: Jan 2000
Location: Salt Lake City, UT, USA
Posts: 5,390
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 31
That's the same thing I was talking about....
We take a bouquet of channels (basically, a "group" of channels in a single, wide digital group), and use the trans-modulator to "compact" the very-wide QPSK signal in to a 6 MHz (in the USA) QAM signal. It only moves the entire RF channel in to a new mode (QAM), where standard Cable QAM TV sets can use it.
The individual channels have to be MPEG-2 SDTV or HDTV (for most currently available sets) and non-encrypted (or, the sets would need their own, individual descramblers).

You might look at something like that, if you wanted to produce and encode everything at one location, and then transmit it via satellite (or, whatever) to many locations around the region or country. You'd need modulators for each channel, but you could trans-modulate the l-band from a dish, and distribute it via a typical RF MATV or cable system.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
kenglish is offline  
post #7 of 9 Old 04-08-2013, 02:18 PM
AVS Special Member
 
sneals2000's Avatar
 
Join Date: May 2003
Location: UK
Posts: 7,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Liked: 43
Quote:
Originally Posted by kenglish View Post

That's the same thing I was talking about....
We take a bouquet of channels (basically, a "group" of channels in a single, wide digital group), and use the trans-modulator to "compact" the very-wide QPSK signal in to a 6 MHz (in the USA) QAM signal. It only moves the entire RF channel in to a new mode (QAM), where standard Cable QAM TV sets can use it.
The individual channels have to be MPEG-2 SDTV or HDTV (for most currently available sets) and non-encrypted (or, the sets would need their own, individual descramblers).

You might look at something like that, if you wanted to produce and encode everything at one location, and then transmit it via satellite (or, whatever) to many locations around the region or country. You'd need modulators for each channel, but you could trans-modulate the l-band from a dish, and distribute it via a typical RF MATV or cable system.

Yes - receiving a DVB-S/S2 transponder demodulating to a transport stream and then remodulating as a DVB-T stream (with possibly a bit of processing of the relevant housekeeping bits) is not uncommon in Europe. It's used as a way of distributing satellite services in mountainous regions where direct terrestrial AND direct satellite reception are impossible (DVB-S/S2 dishes on high ground re-broadcasting in DVB-T) or CATV where DVB-S/S2 services are rebroadcast as DVB-T within apartment buildings without re-encoding.

However I think the OP is suggesting using DVB-T as a distribution system for content that may not be sourced from an existing broadcast source and instead sourcing from baseband HDMI/Component/SDI etc. (i.e. DVD, Blu-ray, Digital signage generators etc.)
sneals2000 is offline  
post #8 of 9 Old 04-09-2013, 07:32 AM
AVS Special Member
 
kenglish's Avatar
 
Join Date: Jan 2000
Location: Salt Lake City, UT, USA
Posts: 5,390
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 31
Yeah, I think it would be an ideal method to use for distributing his content over a wide area (like Cyprus), and just setting the TV sets to the appropriate channels where needed. Here in the US, we even had something called ITFS, which was a microwave service (2 GHz band), which used standard 6-MHz channels for Instructional TV. Something similar could carry quite a few TV channels, especially at low bit-rates per channel. Places like bars, transportation stations and airports, convention centers and hotels, could just use a downconverter, antenna, and standard TV sets for their display needs.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
kenglish is offline  
post #9 of 9 Old 04-09-2013, 05:45 PM
AVS Special Member
 
sneals2000's Avatar
 
Join Date: May 2003
Location: UK
Posts: 7,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Liked: 43
Quote:
Originally Posted by kenglish View Post

Here in the US, we even had something called ITFS, which was a microwave service (2 GHz band), which used standard 6-MHz channels for Instructional TV.

There's an equivalent in Europe called MMDS - which is kind of like microwave cable. http://en.wikipedia.org/wiki/Multichannel_Multipoint_Distribution_Service It's in use in Ireland, Iceland and quite a few other locations. Originally analogue, now increasingly DVB (both DVB-T and DVB-C can apparently be used) Used in the 2.5-2.7GHz bands mainly. Doesn't have the bandwith of cable or satellite, but has more useful bandwith than OTA.
sneals2000 is offline  
Reply HDTV Technical

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off