DTV Subchannels in Canada's Future? - Page 4 - Canadian TV, Computing and Home Theatre Forums

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post #46 of 81 (permalink) Old 2010-10-28, 09:13 AM
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Originally Posted by byebye_cable View Post
How would, for example, french CBC stream english audio track? How many times have I seen something cool on french CBC I wish had an english track...
Transmitting it is easy. The hard part would be producing it (paying for voice actors and engineers to add the tracks), and adding circuits in the audio chain to support another audio track.
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post #47 of 81 (permalink) Old 2010-10-28, 10:25 AM
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^^^^
As mentioned, SAP has already been around for years. Supporting additional audio channels is a lot easier with digital than analog. It's simply additional audio streams added to the existing signal. With SAP, it required additional equipment and separate audio channels from the source, to carry a second language.
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post #48 of 81 (permalink) Old 2010-10-28, 11:26 AM
 
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So with digital it's now easier to add a secondary audio track, and no subchannel required.

I wonder if (for programs that have two audio tracks already available) if CBC would consider making the program available in both languages? I'll bet many of the programs they have are English first & dubbed into French & therefore would indeed have two audio tracks available.
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post #49 of 81 (permalink) Old 2010-10-28, 12:44 PM
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You're still stuck in technical mode. There is the question of the rights issue, too. I doubt that CBC English Television buys Franch rights for the programs it broadcasts, and, AFAIK, English and French televison operate separately, so even coordinating the rights to programs both units happened to have bought might not be too easy.

And, just a f'rinstance, I don't think the NHL or RDS would be too happy if the CBC added french audio to HNIC!
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post #50 of 81 (permalink) Old 2010-10-28, 02:27 PM
 
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We might want to go for the 7 second delay on the live Don Cherry translation to french
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post #51 of 81 (permalink) Old 2010-10-29, 07:43 AM
 
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1080i plus 720p sub channel

My vote would be 1080i @ 14mbps main channel and 720p @ 5mbps sub. Even more so, if it were possible to have variable bitrate, to bump the 1080i channel to 16mbps for events such as HNIC. If the 720p MPEG2 channel was at 3mbs only periodically, it should be fine.

1. Most US networks seem to broadcast 1080i at 11-13 mbps and with the exception of fast moving sports etc, they look good.
2. Canadian networks get most of their HD programming from US networks anyway, and if the same program is shown on both channels, to my eyes they look equal regardless of the Canadian channel higher bitrate.
3. KCPQ from Seattle broadcasts on RF13 at 14mbps and also on the RF25 subchannel at 5mpbs. Doing quick A/B testing, my own "perceived" difference in video quality was not huge. The 5mbps bitrate 720p channel "looked" perhaps 15% lower quality. Slightly noticeable, but not drastic.
4. KCPQ 720p channel @ only 5mbps is still a big improvement over any of my 480i SD channels (even if 7-8mbps).
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post #52 of 81 (permalink) Old 2010-10-30, 10:12 PM
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My vote would be 1080i @ 14mbps main channel and 720p @ 5mbps sub. Even more so, if it were possible to have variable bitrate, to bump the 1080i channel to 16mbps for events such as HNIC. If the 720p MPEG2 channel was at 3mbs only periodically, it should be fine.
The problem is that you have to differentiate between real-time encoding and offline encoding. This is what did in Global's sim-subs when they took HD signals, decoded them, slapped on the Global logo, and re-encoded with a an el-cheap encoder. The result was garbage. In the case of a movie or "taped" production (who uses tape anymore?) you can use the same cheap encoder in a slower mode, and get better quality compression. Have you timed compressing a 3-gigabyte text file with zip versus bzip2? Same principle here.

For live (i.e. real-time) stuff, don't expect better than 2 720p channels at approximately 9 megabits each.

OTA brings you crystal-clear, uncompressed HDTV, no simsubbing, and the real SuperBowl commercials. You can't get all that on satellite... OR CABLE.
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post #53 of 81 (permalink) Old 2010-10-31, 10:56 PM
 
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The problem is that you have to differentiate between real-time encoding and offline encoding. This is what did in Global's sim-subs when they took HD signals, decoded them, slapped on the Global logo, and re-encoded with a an el-cheap encoder. The result was garbage. In the case of a movie or "taped" production (who uses tape anymore?) you can use the same cheap encoder in a slower mode, and get better quality compression. Have you timed compressing a 3-gigabyte text file with zip versus bzip2? Same principle here.

For live (i.e. real-time) stuff, don't expect better than 2 720p channels at approximately 9 megabits each.
I have yet to hear of a DTV broadcaster that does not use real time encoding exclusively to feed the ATSC transmitter. Most programming comes off digital servers which operate at a much higher data rate (50 to 100 Mbps) than ATSC broadcast so the content is decoded to HD-SDI, routed through the master control and encoded live at ATSC rates.

Global ran into problems when they tried to use heavily compressed Fox affiliate feeds during sports events. Fox has a unique distribution system which feeds MPEG signals to affiliates at ATSC data rates (less than 19 megabits per second) while the other 3 big US networks feed signals at about 40 megabits per second for decoding at the local affiliate. In the Fox distribution system an MPEG switch connects either the Fox network feed or the local affiliate's encoder to the transmitter.

The issue had nothing to do with Global's encoders rather it came from recompressing Fox feeds that had already been heavily compressed for ATSC transmission. The problem got really bad when all Fox regional feeds were carrying the same live NFL game which resulted in the Fox statistical multiplex processing getting squeezed to the limit at the satellite uplink.

That said, I agree that 2 programs at 720P are the most HD feeds any broadcaster can expect on an ATSC channel. The two encoders have to operate in a statistical multiplex mode and employ detail reduction pre-filtering to minimize macroblocking. The quality will be best when both services are carrying programming produced at 24 frames per second (dramatic TV series and movies) and worst with live sports.
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post #54 of 81 (permalink) Old 2011-01-24, 09:21 AM
 
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TVOntario intends on digital transmitters in a number of markets where CBC will be eliminating OTA service. TVO should consider broadcasting CBC on digital subchannels in London, Kitchener, and Thunder Bay (which will no longer have a private CBC affiliate) until such time CBC can have its own stations in those cities. I would have no problem with provincial funding going towards this, although CBC should foot some of the bill.

Doesn't help areas like Moncton though.
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post #55 of 81 (permalink) Old 2011-01-24, 10:56 AM Thread Starter
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CBC is a national broadcaster largely funded by the public purse. I'm not so sure that very many areas that have CBC OTA now will lose CBC's OTA coverage post transition, however, in some areas where CBC will no longer reach via OTA, the TVO subchannel idea would be a great idea as long as TVO does provide such remote area coverage. The downside is that CBC on a subchannel would only be SD, but still CBC-SD would be better than no CBC at all.

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post #56 of 81 (permalink) Old 2011-02-02, 10:21 PM
 
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I still like the idea I suggested a few years ago - minority language SD subchannels, e.g., SRC in SD with CBC in HD in Anglophone markets, CBC in SD with SRC in HD where French is dominant, saving the expense of building out two whole transmitters.

Windsor is one example where this could work very well. Either a single transmitter on 35 could carry both networks with superior coverage (compared to the highly directional CBET 9 facility), or a really cheap conversion of channel 9 for both networks.

Of course, some communities (Montréal, Ottawa, Sudbury, Winnipeg, and others) really call for separate HD facilities for each.

It could also have been used to provide TFO in SD over the greater TVO gird, though now TFO is no longer connected to TVO.
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post #57 of 81 (permalink) Old 2011-02-14, 02:45 PM
 
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Exclamation Subchannels in Canada

No plans to utilise subchannels is not a surprise.

Public broadcasters need to lead the way in leveraging the increased capacity of digital TV. Additional channels already exist and should be freely broadcast - at least in the major metroplitan areas. Surely a boon to their own advertisers! It is quite bizarre that the switch to digital TV in Canada is basically being done as a one for one mapping of old analogue broadcasts and catching up with 1964 by migrating from VHF to UHF.

It all seems to coincide with the oligopolistic structure of the industry.

If US channels can routinely carry two additional TV subchannels, and if Freeview in the UK can offer "up to 50 digital TV channels and 24 radio stations with no subscription" it is time for Canada to do more than simply do one for one remapping of half a dozen channels for a lucky few.
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post #58 of 81 (permalink) Old 2011-02-14, 03:05 PM
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Additional channels already exist and should be freely broadcast
The CRTC has made it clear that they can't use existing channels nor can they broadcast anything that would compete with existing channels.
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post #59 of 81 (permalink) Old 2011-02-14, 03:07 PM
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Actually, there doesn't appear to be a transition from VHF to UHF in Canada.

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post #60 of 81 (permalink) Old 2011-02-14, 03:46 PM
 
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The CRTC has made it clear that they can't use existing channels nor can they broadcast anything that would compete with existing channels.
Roger 1818 - Thanks for the info (do you have the source please for us rookies?), but I think that is my point. The CRTC should NOT be in the business of restricting free-to-air transmissions beyond the technical limitations of the medium and preventing co-channel interference. Could it possibly be regulatory capture by the Cable/Satellite industry?

Jase88 - okay, ty, I happily stand corrected.
Out of interest, seeing all the original Buffalo US channels 2, 4 and 7 are broadcasting now high up in the UHF spectrum, any idea why Canada is continuing with VHF?
Would it not be better to sell off the capacity and make some $ to invest in an extensive digital transmitter network?
It just seems bizarre that /A\ Channel Barrie is widely distributed on cable (and presumably satellite) throughout the GTA but no subchannel is to be used for it under CTV in Toronto or Kitchener. Such a lost opportunity for genuine commercial TV to stand alone.
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