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Old 2011-09-25, 11:46 PM   #1
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Default CRTC's "HDTV Must Not be Degraded" policy.

This is in reference to this discussion:

http://www.digitalhome.ca/forum/showthread.php?t=84230

I am wondering what has happened in regards to this since 2008. It seemed like the CRTC was looking toward a policy that wouldn't allow BDU's to recompress or degrade HDTV signals. Now we all know that the various BDU's in Canada recompress their HDTV signals to differing degrees. The satellite companies probably more then the cable companies due to more bandwidth limitations, especially in Shaw Direct's case. It seems most cable companies use 3 HDTV channels per QAM, and Shaw Direct uses 3 channels per transponder using 8PSK modulation, which certainly requires recompression of the original signals since most broadcast HDTV signals are around 19Mbps, and I think each transponder has around 38Mbps capacity. Which would put each channel in the neighbourhood of 12-13Mbps of bandwidth.

But my real question is did this policy just die? Has it been over-ruled? Is it just ignored and the CRTC has no was to enforce it? Did consumers ask for more compression considering we want more and more HDTV channels?

I tried to find more information on the CRTC website but wasn't successful. Does anybody have more information on this?

Thanks
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Old 2011-09-26, 03:08 AM   #2
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most broadcast HDTV signals are around 19Mbps
This includes a fair amount of overhead, in the way of error correction information, and uses the relatively inefficient MPEG2 compression scheme. HDTV signals can be fit into less bandwidth by using better encoding and compression schemes. Shaw Direct's HD signals are actually fairly good. I occasionally notice some picture degradation but that can be from the source since some HDTV stations reduce bandwidth themselves by using sub-channels. Bell TV is by far the worst offender when it comes to picture degradation and reducing bandwidth to add extra channels. They get around the regulation by getting the broadcaster to supply a lower resolution picture using a direct link. For every regulation, there's a loophole.
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Old 2011-09-26, 11:12 AM   #3
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Shaw Direct's HD signals are actually fairly good. I occasionally notice some picture degradation but that can be from the source since some HDTV stations reduce bandwidth themselves by using sub-channels.
Yesterday's NFL games on Shaw Direct looked absolutely horrible - compression artifacts everywhere and on multiple affiliate stations. This continued into the night with the presentation of The Amazing Race.
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Old 2011-09-26, 11:32 AM   #4
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Originally Posted by Raptor256 View Post
since most broadcast HDTV signals are around 19Mbps
Most Canadian services backhaul their signals to the BDUs over fibre - the 19Mbps number is specific to OTA broadcasts. So in reality, the HD signal Shaw, Bell or Rogers gets from the broadcaster could be anything from uncompressed baseband (1.5Gb/s) to something between 30 and 50Mb/s MPEG-2.

You need to review the whole acquisition->broadcast chain to appreciate how much compression is in play throughout.

HDCAM (144 Mb/s) and HDCAM-SR (440 Mb/s) are by far the most popular HD tape delivery formats for television programming in the broadcast world. However, with the recent Japanese Earthquake/Tsunami crisis, a number of key factories were affected causing huge tape shortages. This has made a massive push on the industry towards file-based delivery methods.

But even further up the chain, XDCAM-HD (50Mb/s) is emerging as one of the most popular broadcast production camera formats. This is disc-based recording media but there is now a memory-card based version (XDCAM-EX) at 50Mb/s also.

Uncompressed HD (1.5Gb/s) production exists but is not too common and obviously expensive given all the resources required to manage it.

And depending on the storage servers (Evertz, Omneon, Nexio) used by the broadcaster for ingesting of media (tape or file), an additional level of compression is applied. XDCAM-HD @ 50Mb/s is again emerging as a new common standard for storage of media for broadcast. It also happens to be edit-friendy (Final Cut Pro, Avid).
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Old 2011-09-27, 06:29 PM   #5
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Canadian BDUs get their signals OTA, by satellite or through direct fibre connections to the programming service. The fibre facility cost may be paid by the BDU or the programming service depending on the business deal. The interface for HD is either HD-SDI (1.5 Gbits/sec) using the programming service plant standard (1080i or 720p) or MPEG2 at a data rate less than 19.3 Mbits/sec. As part of the business deal, the programming service may allow the BDU to change the HD standard to meet the BDU's requirements. In this case the BDU will usually install the format convert and HD encoder at the programming service location. If the programming service is satisfied with the quality provided by the BDU then there is no problem and no violation of CRTC policy.

HD picture quality doesn't drive subscription revenue so most programming services will accept something less than the absolute best if it doesn't have any meaningful effect on subscription revenue. If lower quality means three HD services per channel and opens the door to distribute more of the company's programming services in HD then quality will take the hit. Fortunately, HD encoders and statistical multiplexers keep getting better so quality remains acceptable for the vast majority of viewers even with a 3 channel multiplex. There are certainly examples of incompatible services being placed in a multiplex without due consideration of image complexity. High activity, high detail programming tends to heavily stress MPEG systems so HD sports channels should not be put together in the same multiplex.

The CRTC said "program signals should be of the same quality and in the same format as those received by the BDU, without any degradation." The CRTC wanted to protect HD quality and prevent the BDUs from doing whatever they wanted to signals without restraint. The language allows a broadcaster, programmer or viewer to raise a complaint if a BDU reduces signal quality. The key word in the quote is 'should' because it gives some flexibility for interpretation. If a BDU and programmers agree to lower picture quality in order to make more HD services available then the trade-off is acceptable. If thousands of viewers complain about quality then the Commission would probably react while nit picking complaints from a few will probably be ignored. Like most things in life, balance and pragmatism rule.
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Old 2011-09-27, 07:47 PM   #6
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Shaw Direct uses 3 channels per transponder using 8PSK modulation, which certainly requires recompression of the original signals since most broadcast HDTV signals are around 19Mbps
I don't have any way to look since Shaw uses DCII format on their satellite feeds.
But starting with an 8PSK Symbol Rate of 20500, and an FEC of 2/3 (as published on lyngsat) I estimate roughly 40 Mbps of BW available on a typical Anik F2 8PSK Transponder. I would say they have a little bit more BW per Physical channel than cable does.
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Old 2011-09-28, 12:33 AM   #7
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program signals should be of the same quality and in the same format as those received by the BDU
Therein lies the problem. Bell can and has coerced broadcasters into providing lower quality signals for rebroadcast on their service. The result is lots of HD channels with uniformly poor quality. Most customers won't know the difference unless they do a direct comparison with a high quality HD signal. I was impressed with the quality of most HD signals on Shaw, when compared to Bell. However, I don't watch all the channels and Shaw's signals are often far from perfect. They can also suffer from comparison with some OTA signals.
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Old 2011-09-28, 07:08 AM   #8
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Bell can and has coerced broadcasters into providing lower quality signals for rebroadcast on their service. The result is lots of HD channels with uniformly poor quality.
Bell actually strongly urges or demands broadcasters provide the highest quality signal possible, HD-SDI. This is because they themselves will recompress it to such a large degree, they need that initial quality headroom.
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Old 2011-09-28, 10:55 AM   #9
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Originally Posted by majortom View Post
I don't have any way to look since Shaw uses DCII format on their satellite feeds.
But starting with an 8PSK Symbol Rate of 20500, and an FEC of 2/3 (as published on lyngsat) I estimate roughly 40 Mbps of BW available on a typical Anik F2 8PSK Transponder. I would say they have a little bit more BW per Physical channel than cable does.
Shaw provides signal distribution services to Canadian specialty and pay-tv programmers so the 3 HD multiplex is designed to fit within the constraints of a 256 QAM cable channel with a useful data rate of 38.8 Mbits/sec. Some of the capacity of the QAM channel is used by overhead data so the allowable rate for program services will be around 38 Mbits/sec. The average data rate of about 12 Mbits/sec per service will provide acceptable quality if the multiplex is built properly with program services that have complementary statistical properties.

In all the discussion of compression, people need to remember that MPEG 2 broadcast compression is near 100 to 1 and that cable and satellite are similar. The big problems occur when a BDU tries to put 3 HD signals from OTA into a multiplex using an open loop statistical multiplexer. A much better approach is to decode the HD signals and re-encode using 3 HD encoders tied to a closed loop statistical multiplexer. The cost is higher but the results will be better provided that the OTA HD signals are good quality.
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Old 2011-09-28, 12:45 PM   #10
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Alright guys I find all this very interesting.

The thing that made me start this conversation is my own cable to satellite experience.

I had been a Shaw Cable customer in Winnipeg, but recently became a Shaw Direct customer because of a move. One thing I noticed was that the satellite signal wasn't quite as good as the cable signal when it came to HD quality. What I really notice is more macroblocking on the HD channels, especially with fast movement, then I ever saw on Shaw cable, and I am curious about why that might be.

Could some of these quality issues be fixed if Shaw Direct went 100% MPEG4 and used the extra bandwidth to increase quality instead of putting another channel on any 1 transponder?
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Old 2011-09-28, 02:27 PM   #11
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MPEG 4 would certainly increase capacity and might be configured for higher quality. The obstacle to any standards change is the number of existing receivers that don't have the MPEG 4 decoder. A new decoder is not a software download as hardware decoders (chips) are used in digital set top boxes. The BDU will have to run an upgrade program to provide customers with replacement receivers or PVRs before making a wholesale change.
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Old 2011-09-28, 06:32 PM   #12
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Ya I realize that. And I'm sure Shaw has a huge amount of non-MPEG4 hardware out there, and would be very hesitant to have to take any monetary hit to make it happen. Maybe when Anik F3 is in position the new channels will be MPEG4 only and they will use that as incentive. Honestly, considering Shaw has basically tapped out all their current satellite capacity I wish they would just go "Apple" and cast off their old hardware for the good of the system at large, and free up some capacity for some of the newer HD channels that have come out. Or even better, lets ditch the plethora of PPV, and Big 10 Sports while we're at it, and create some capacity for real channels.
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Old 2011-09-28, 06:45 PM   #13
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macro blocking doesn't necessarily mean there is a lack of bandwidth on the channel carrying the program. Could also be caused by transmission errors. How confident are you in the installation of the dish? It's a relatively new install right? 8PSK signals are more touchy, more sensitive to antenna misalignment than legacy QPSK signals are carrying SD programs. Have you asked around in the Shaw Direct forum to see what other Shaw Direct Users are experiencing? Does every Shaw Direct user report the same issue?
Again, I don't have any way to look myself, but just thought I'd throw that out there.
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Old 2011-09-29, 10:30 AM   #14
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Originally Posted by Raptor256 View Post
... Maybe when Anik F3 is in position the new channels will be MPEG4 only and they will use that as incentive. Honestly, considering Shaw has basically tapped out all their current satellite capacity I wish they would just go "Apple" and cast off their old hardware for the good of the system at large, and free up some capacity for some of the newer HD channels that have come out. ...
Conversions are hugely expensive and disruptive to the customer base. In addition to the cost of the new customer hardware, there is promotion and advertising, customer service, technical support and shipping. Some customers have zero technical skill and will want an installer to do the work, for free. Some compensation is required because customers will feel the changeout is a hassle so incentives like free programming are required.

As a theoretical example not related to any real company, assume $100 per receiver replaced which would be a bargain basement price. If a BDU has a couple hundred thousand HD recceivers to replace then the cost will be around $20 million.

New compression equipment must be installed which will obsolete the displaced gear. There is also a compatibility issue for channels used by cable companies that will require MPEG 4 to MPEG 2 conversion and multiplexing to rebuild the 3 channel multiplexes. Lots of engineering, coordination and project management costs. The cost of this work is hard to estimate as it depends on the number of channels and locations involved but $5 to $10 million is a useful assumption so conversion to MPEG 4 would be a $25 to $30 million project in this example.

The best approach to introduce new technology is often to incorporate it into receivers and let the base build up over time. Additional features in the new equipment may incent existing customers to voluntarily upgrade. New customers will get new equipment and some existing customers will leave. Eventually the point will be reached where targeted upgrade programs for customers of specific program packages, say pay tv or sports, becomes economically attractive. High revenue services like NFL Sunday Ticket require lots of capacity on Sunday afternoon but have relatively small customer bases which could make them a priority conversion.
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Old 2011-09-29, 04:37 PM   #15
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The macro blocking I'm seeing is definitely intrinsic to the signal. I have a well aligned dish, and though it's near the 60th parallel, we haven't had any digital video breakup or audio glitching, which is very apparent. While my signal isn't as strong as other people in this forum has, it certainly seems to be well within what Shaw Directs implementation of FEC allows for. If I was losing any statistically significant number of bits it would be pretty apparent. Especially on an MPEG2 stream.
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