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HDTV must not be degraded: CRTC

19K views 75 replies 29 participants last post by  studlygoorite 
#1 · (Edited)
This thread is to discuss the current and growing practise by most TV broadcast distributors (cablevision, satellite, telco, etc) to re-compress HDTV channels to use less bandwidth.

In many cases this additional compression results in degradation of the image by causing soft edges (mosquito noise), macroblocking and adding other errors and artifacts.

This additional compression is in violation of CRTC directives that state:
program signals should be of the same quality and in the same format as those received by the BDU, without any degradation.
In fact, not only HD but also SD digital TV stations are covered. For reference I will post the relevant sections of the CRTC notices.

Do you want the distributors (Shaw, Rogers, etc) left to decide how much compression is too much? Or do you want your HDTV channels in the original quality that the broadcaster intended and provided?

You can submit a complaint to the CRTC stating that you object to the image degradation caused by additional compression the distributors are applying to the HD and SD digital TV signals you receive from them, in violation of CRTC notices 2006-74 and 2003-61.
 
#30 ·
Just wanted to suggest that if you file a complaint, the CRTC will likely insist that you give at least 1 specific example. So, find a program (say on Discovery) and specifically mention the day, time, and channel.

(You can additionally mention that it happens with other programs, to add some extra weight to your complaint, but at least the one example is usually a requirement)

And I would like to emphasize as well that the volume of complaints will help things, especially for a subjective matter like this. If the CRTC gets 100 complaints saying the image quality has decreased noticeably, they will likely take it fairly seriously, vs. 5-10 people. In the past convincing the CRTC that one broadcast is of higher quality than another has been not very successful.

It would possibly be useful to pass all the information from the Comcast situation with links to the pictures that compare the quality to demonstrate to the CRTC that, in general, recompressing signals to a lower bitrate will cause noticeable degradation of quality.

P.S. Also, make sure you're certain there is a different in PQ before you complain, otherwise, it'll work against you in the long run.
 
#36 ·
CRTC - give specifics

Just wanted to suggest that if you file a complaint, the CRTC will likely insist that you give at least 1 specific example.
You are dead on with your advice. I just heard back from the CRTC on my complaint:
Thank you for taking the time to contact the CRTC with your concerns.

We do appreciate what you are telling us; however, as noted in our attached fact sheet on the complaints process: http://www.crtc.gc.ca/eng/INFO_SHT/G8.htm , in order to investigate complaints, we require the identification of a particular broadcast, i.e. time and date.

Should you wish to write back with details of broadcasts that typify your concern, we will be pleased to follow up on your behalf. In the meantime, I hope this is helpful.
So include at least one specific date/time/program in your complaint. I'll be sending more details for mine.

From the CRTC link:
  • Identify the radio or television station involved by name or call sign and location.
  • Provide the date, time and name of any program or advertisement that prompted you to write.
  • Identify cable companies involved by name and location.
  • Identify satellite or other wireless distribution services involved by name and your location (i.e. town or city and province).
 
#33 · (Edited)
Article on HDTV and multiplexing

HDTV broadcasting and multiplexing (signal-combining) is a rather technical subject. So if you don't want to know how it works, just skip this post.

I found an article that gives some background on how HDTV signals are carried through the system and how the bitrate can be manipulated to trade off quality for quantity.

But first, here's my explanation of some terms from the article...

"MPEG-2"
I'll assume you are familiar with JPEG (.jpg) compression, which is used to reduce the file size of still pictures. MPEG-2 is the equivalent for compressing motion pictures, and it is used to reduce the bandwidth (bitrate) of HD signals. And just as with JPEG, the more you compress the signal the worse the image looks.

"multicasting" (not multiplexing)
In terrestrial broadcasting (ie. Over The Air) there is 19.4 Mbps of bandwidth available. The original broadcaster (eg. a PBS station) can decide to use all of that for the HD signal or they can do something called "multicasting" which means they use a lower bitrate for the HD signal to leave room to also broadcast an SD signal or other data. That is a decision made at the source.

But a high-quality HD signal will usually be allocated the full 19.4 Mbps of bandwidth so that it can peak up to that rate and still look good during scenes with lots of motion, even though the average bitrate of the signal is going to be lower thanks to scenes with little or no motion.

"multiplexing"
Multiplexing is what the distributor (Shaw, Rogers, etc) does to combine multiple broadcast signals together after they receive them.

The distributor has channels of 38.8 Mbps that they use to send the broadcast signals to the subscriber (you). Doing the math, each 38.8 Mbps channel can hold 2 HD signals with a bitrate of up to 19.4 Mbps each. That means the distributor can multiplex (combine) 2 of those high-quality HD signals together onto the channel without having to further compress them and compromise their quality.

But if the distributor decides they want to multiplex 3 HD signals (3 x 19.4 = 58.2 Mbps) onto that 38.8 Mbps channel instead of 2, then things get tricky.

They either have to start with signals that don't use the full 19.4 Mbps (eg. lower-quality HD) or they have to compress the high-quality 19.4 Mbps HD signals down so that they use a lower bitrate, with the result that they have lowered the quality of the HD.

A compromise solution is to use "statistical multiplexing", which means rather than compressing everything all the time, you instead compress only as much as needed at each moment to bring the combined 3 signals down to a total of 38.8 Mbps. If you're lucky, 2 of the signals will be very low motion (low bitrate) when the 3rd is high motion (high bitrate) and it will still all fit in 38.8 Mbps. Nice theory, but in reality the signals don't get through so cleanly... they just get compressed a little less than with non-statistical multiplexing.

That, in a nutshell, is the problem with trying to multiplex 3 HD signals together.

Now with that explanation out of the way, have a read of this article and see if it helps you make further sense of what is going on.

HDTV Data Multiplexing

And if you find other articles that help explain the technology of how our HD is being degraded, please link them.
 
#42 ·
...A compromise solution is to use "statistical multiplexing", which means rather than compressing everything all the time, you instead compress only as much as needed at each moment to bring the combined 3 signals down to a total of 38.8 Mbps. If you're lucky, 2 of the signals will be very low motion (low bitrate) when the 3rd is high motion (high bitrate) and it will still all fit in 38.8 Mbps. Nice theory, but in reality the signals don't get through so cleanly... they just get compressed a little less than with non-statistical multiplexing...
Very interesting and is probably why the macroblocking varies from time to time. Thanks for posting.

I have filed my complaint with the CRTC and provided last nights hockey games on both TSN HD and CBC HD as the prime examples.

Hopefully something comes out of this!
 
#34 ·
Any cable company using a QAM for 3 HD channels is not providing quality picture which HD clients deserve to have.

Videotron's Illico digital service limits QAM's for HD to 2 channels. See:

http://illico2.tripod.com/NumMtl200803.html

The single exception here is QAM # 40 which carries 10 SD channels (all SportMax) plus SportMax HD (1280 x 720 ), channel 662. And that is because SportMax puts everything in the same pipe. I believe Videotron can't do anything about that.
 
#37 ·
There in lies the problem
Some people want quantity, while others want quality
I think the providers feel that most people are happy with reduced PQ, as they are new to HD, and it still blows them away
A small minority, who have either have bluray, hd dvd or have had HD for a while from their cable/satellite provider DO notice the difference, but again, it seems most want MORE HD, instead of HD lite
 
#38 ·
Well I think ceratain services will improve like Bell will probally switch to MPEG4 soon which should help a bit, SDV for cable could help... and of course all are problems might be solved when Fiber TV comes to the market :) which i'm guessing might show up slowly in ceratin areas near the end of the year.
 
#43 ·
The following is aimed at cablecos. One of the major causes of "insufficient bandwidth", which is used to justify compression, is unnecessary duplication of channels. there are two major categories...
  1. "Time shifting", which carries the same set of programs multiple times. OF COURSE the BDU runs short of bandwidth. What do you expect? Solution; cut down on timeshift channels, and sell more PVRs.
  2. Multiple-quality-level feeds of the same channel. A of channels are broadcast in 2 or 3 of...
    1. clear analogue (NTSC), which requires 6 mhz of bandwidth
    2. digital SDV, which requires 1 mhz of bandwidth
    3. digital HDTV, which requires 3 mhz (1/2 of a QAM) bandwidth
    Solution; rent/sell boxes with 3 differnet types of outputs. The el-cheapo STB would have analogue output only. The next step up would have analogue and composite outputs. The top-of-the line box would have analogue and composite and component outputs, along withappropriate audio outputs (I'm not an audiophile, so am lost here).
 
#48 ·
I have always believed that the cable cos should just eat it and give out digital SD boxes to everyone that is still on analog SD and then shut it down. That would free up SCADS of BW and allow for a couple hundred HD channels.

As for the obvious question of how many for each household, I would say one each and a discounted rental (12 months) or purchase on any additional that are needed. If your household already has digital STBs, then you would just get the discounted rental or purchase.

I would also have to think that this would be a less expensive route to take so that they (cable cos) can then concentrate on getting out to all of the rural areas that are still under or non serviced.

And the cream on all of this is that the more digital STBs, the more PPV that they can peddle and that is all high profit content.
 
#52 ·
Shaw second-level TS called me today in response to my CRTC complaint.

They were clearly trying to dodge the issue.... would I like to be switched to the all-digital map (no, my analog is probably better looking than the over-compressed SD I'd get).... what is the refresh rate on my TV... bunch of other nonsense.

I answered his questions, but when I asked my questions... what is the bitrate of your incoming signals vs the bitrate you send to me... I get "Sir, we don't give that type of information to our customers."

He asked me if I'd like to talk to someone else. I said sure, if that person will be honest about what Shaw is doing with their signal compression... otherwise Shaw should just respond to the CRTC complaint.

They have until May 7th (3 weeks after the CRTC notice) to respond. I'll let you know if I hear anything further in the meantime.
 
#55 ·
Heard from Shaw again...

I heard from Shaw again about my CRTC complaint. Got a call at 8am on Friday from Dale Henderson (yes, the guy who didn't get back to Hugh after the Shaw audio dropout testing).

At least he was more willing to talk about compression than the last fellow who called me from Shaw.

That is, after I got him past the idea that I was mistaking signal drops for macroblocking. I said he was welcome to send someone to check my signal, but just a few days ago (for a different purpose) I had posted a page showing the difference, so I sent him the URL and he can judge for himself if I can tell the difference. Nobody has called to check my signal yet.

But I didn't make a lot of progress with Dale. He wasn't sure the CRTC had really said that BDU's can't degrade the signal from its original quality (I have since emailed him the direct links and quoted the text). And he tried to confuse the issue by questioning what that would mean if they move to MPEG-4. But I brought him back to the fact that most (all?) of the signals they use start as MPEG-2 and are distributed as MPEG-2... and if it starts as a certain MPEG-2 bitrate and they reduce that bitrate, how can they claim they are not degrading it?

He also touched on stat muxing, available bandwidth, multicasting, QAM 64 vs QAM 256, and a few other points all meant to make me believe Shaw is delivering the best HD they can. But Rogers delivers as much or more HD and isn't using additional compression (yet).

At the end he said he was going to read my emails and get back to me. Despite asking if I'd be home the rest of the day, he didn't call again. In any case, they have to give a written response to my complaint later this week.

p.s. I couldn't resist mentioning I thought it was a bad PR move to leave Hugh and the audio dropout test group hanging. He said that working with forum groups can be problematic, but they have made a lot of improvements and are happy to address customer issues on an individual basis.
 
#56 ·
I heard from Shaw again about my CRTC complaint. Got a call at 8am on Friday from Dale Henderson (yes, the guy who didn't get back to Hugh after the Shaw audio dropout testing)..............

p.s. I couldn't resist mentioning I thought it was a bad PR move to leave Hugh and the audio dropout test group hanging. He said that working with forum groups can be problematic, but they have made a lot of improvements and are happy to address customer issues on an individual basis.
Problematic? For Shaw maybe but not us. I guess the legal department told him he was digging his own grave so he stopped. Individuals are far more easy to placate.
 
#57 ·
Shaw responds to CRTC complaint

I received my official (.cc to the CRTC) response from Shaw today:
Shaw Response page 1
Shaw Response page 2

It seems to go off on some tangents, addressing issues and questions I never asked. I'd call it bobbing and weaving, trying to duck the central issue... that they degrade the original signal with extra compression.

On the bright side, they confirmed to the CRTC what we already know... it is their standard practice to pack 3 HD channels per QAM (or 10-12 SD).

Unfortunately they didn't get into any specifics about the bitrates of the original signals they receive, so it is not quite as clear (except by inference) that they are in fact downgrading those signals.

I guess my next step is to add more comments to my CRTC complaint explaining that by packing 3 HD per QAM Shaw is degrading the signal of many (perhaps all) of the HD channels they carry. And therefore this is a regulatory issue they need to take up with Shaw.

It's not strictly necessary, but I think it would bolster my argument to be able to say that 3 HD per QAM is not the standard used by some other BDUs.

So as an example of the right way to deliver HD, can someone confirm for me that Rogers and Cogeco are using QAM 256 and only carrying 2 HD per QAM? I'm sure this has been verified before on Rogers, but I'm not so sure about Cogeco.

Thanks!
 
#58 ·
Rogers Ontario still has two channels per QAM, however, there is a thread about Rogers considering compression in the Rogers forum. It has not proceeded yet.

I believe Cogeco operate similar to Shaw. With the smaller HDD in the PVRs (especially many with the 6412, this is an advantage to some people because they can record more... I believe Rogers Atlantic also doesn't compress, having 2 channels per QAM (for now)
 
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