More Compression Being Used?

MarkB

New member
Is it just me, or does it appear that since the Superchannels and new HD have been added, even if not in the guide, that the Expressvu signal is alot more compressed then it was. I was watching the Riders/Stampeders CFL game today on CBCHD and it appeared that any bit of motion with the red jerseys had some type of artifacts in the picture. At times it was harder to see, but at other times easily noticeable. I am assuming that this is caused by compression by Expressvu and not my tv? I am watching on a 6100 receiver and a 2 week old Panasonic 1080P plasma.
 
Last I checked BEV hasn't added anything else to the transponder that carries CBC HD, and since compression artifacts could only affect stations on the same transponder, it's not likely that's what you're seeing. Unfortunately motion artifact is a fact of like with most of the digital compression algorithms such as MPEG2.

-Mike
 
CBC HD seem to have an exclusive transponder for themself. So they can't be affected.
 
I find it hard to believe that a tv is causing artifacts itself, especially when it doesn't on dvd, Blu Ray, or PS3. CBCHD doesn't look all that bad, but I've really noticed these artifacts on the Centre Ice HD channels. I take it this is due to three channels per transponder. Again, I can really see these artifacts on the white ice surface on fast moving plays. Saturday night, CBCHD looked way better than Centre Ice HD.
 
Just because it's all by itself doesn't' when it's running at full bandwidth.

They could still be grooming it down to make room for new additions and to keep it in the same lower quality as the others so as not to cause any alarms as what FULL HD might look like.

I think you'd really need to analyse the transport stream from that TP and see how many null packets and what data rate is actually assigned to it.

Unfortunately my DVB card with TSReader is offline at the moment or I could probably determine that.
Perhaps some who has a 'tester' friend could ask them to have a look.
All I know is last time I looked SD ran about 2.5 M and HD around 8 or so.
 
That's low for HD if you're referring to Mbps. Should be closer to 15.

A proper setup of the TV can help with macroblocking/compression artifacts. Most TVs come from the manufacturer in torch mode and with all the edge enhancements turned on. These can exacerbate the problem. See:

http://www.digitalhome.ca/forum/showthread.php?t=17713

DVDs, et al are rate shaped to minimize compression artifacts (they are not "real time). Broadcast TV is not rate-shaped, therefore the "live" decoding will show all the warts. The colour red often shows these artifacts very well.
 
It would help if someone is able to provide some stats on bandwidth actually delivered for the CBC East HD transponder (as it is only one) and the compressed sports channels where Bell is putting three live signals into the space of two standard HD.

On paper, it sounds dismal: but perhaps Bell is able to deliver "good enough" MPEG-2 that is compressed 50% more than usual and yet still is acceptable to most folks paying for these premium sports channels.
 
Back
Top