the missing s on profesional degree is not a grammar error it only accounts for the fact that after the concept mistake pointed out by voyager6868 I guess I will have to keep the diploma hidden somewhere and also at least demote myself professionally. Time to go back to school, lol lol.

compression artifacts started to appear and their engineers decided to switch the HD feed to 720p as it is now. so now they have the same PBS HD feed they get at 1080i re-formatted to 720p plus the other 2 standard def 480i PBS channels. But no apparent compression artifacts , and I mean apparent because it all boils down to wether you want to watch the screen only 1 foot away or at least 3 times the height of the screen.

Actually, I remember when PBS Buffalo used to look really good (about 3 years ago). Even though they have switched to 720p to fix some serious face-ghosting and it helped, there just isn't the same detail as other 720p stations (ABC,FOX). Most times it doesn't look too much better than an really good quality upconverted DVD. It's too bad some US stations are sacrificing their PQ to add some extra channels that likely very few people watch. You only have to look at CBS Buffalo to see what a really good compressor with a high bitrate can look like. I think it's the gold standard for OTA channels. A bit off-topic, but just illustrates how important both compression equipment and bitrate are to video quality.

Most times it doesn't look too much better than an really good quality upconverted DVDI assume you're talking about when the programming is HD. A fair bit of their programming is widescreen and is announced as such at the beginning of the programme. They still have some minor ghosting, but the PQ hasn't been bad, but it isn't as good as I remember Spokane 1080i...

Yes, the HD stuff does look better than their widescreen stuff, but the HD stuff still isn't nearly what it used to be. The best examples are some of the 30-second commericals they do where people talk about how PBS changed their lives. These used to look really good, but now there's a definite softness and less detail. Whether this is the fault of PBS or the Buffalo station, I can't say, especially since Rogers doesn't distribute the west coast PBS any more.

I'll be out in Seattle next week with my laptop OTA HD tuner, so I may be able to record PBS out there and make a comparison.

This thread is about Rogers compression, not for comparing sports channels. Several posts deleted.

the uncompressed 663Mbps stream (1280x720x12bppx60fps)

Uncompressed HD (either 1080i or 720p) is 1.485 Gbit/s, not 663Mbps. This is standardized under SMPTE_292M:

http://en.wikipedia.org/wiki/SMPTE_292M

It sounds a lot to have a 77:1 ratio from uncompressed (1.485Gbps) to the MPEG-2 transmitted OTA (19.39Mbps), but it is accomplished through a large variety of means including reducing the horizontal sampling to 3/4 (encoding only 1440x1080 rather than 1920x1080 - see http://en.wikipedia.org/wiki/HDCAM for the compression details of HDCAM which is the predominant tape format used to capture uncompressed HD from the camera), chroma sub-sampling which encodes the color information at half or less the rate of luminance due to the eye's reduced sensitivity to detail in color (see http://en.wikipedia.org/wiki/4:2:0), and MPEG encoding which has various methods including compression within a frame (like JPEG) and between frames ("Long-GOP", where only 1 out of every 15 frames is real and the rest are synthesized based on motion vectors - see http://en.wikipedia.org/wiki/Group_of_pictures).

Incidentally, OTA video should not really be referred to as "uncompressed". I would call it compressed (77:1, as per above)... by comparisson, cable and satellite should be referred to as "re-compressed", bitrate-shifted or stat-muxed.

[...] the uncompressed 663Mbps stream (1280x720x12bppx60fps).

(I tried to post this once but it didn't seem to go through... sorry if it double-posts).

That's not accurate. Uncompressed HD, either 720p or 1080i, is 1.485Gbps as per the SMPTE 292M specification (http://en.wikipedia.org/wiki/SMPTE_292M).

The ~77:1 compression between that signal and the 19.39Mbps (max) HD received in the home is accomplished by a number of methods including:

- when the video is recorded to tape (generally HDCAM) only 3/4 of the horizontal resolution is stored (1440x1080), the high frequencies are removed (low pass filter), the color is reduced to half the resolution as the luminance (chroma subsampling) due to the eye's reduced ability to resolve detail in color (http://en.wikipedia.org/wiki/4:2:0).

- broadcasters either playout directly from tape or encode to then playout from video servers using MPEG-2 at around 35-50Mbps. MPEG-2 uses compression on a frame basis (like JPEG) to discard redundant information, then on a time basis by discarding frames (http://en.wikipedia.org/wiki/Group_of_pictures) so only 1 in 15 frames is actually 'real' and the rest are synthesized on playback using motion vectors as pointers.

- Transmission MPEG-2 encoding uses the same techniques to compress the signal further to 19.39Mbps at best (for OTA), as per the ATSC spec (http://en.wikipedia.org/wiki/Atsc). Cables and Satellite companies can then further compress this by bitrate-shifting/statistical multiplexing.

Given that, OTA should not really be referred to as 'uncompressed' either. I would refer to Cable/Sat. as re-compressed or bitrate-shifted.

well i lost my long post again. summarized version. Ulyses the SMTP standard refers to the maximum uncompressed bit rate and Voyager668 was refering only to the 720p format 1 of the 18 Digital TV formats in the ATSC standard. therefore 663 Mb/s for uncompressed 720p at 60 Hz and 12 bpp was an accurate statement. You are right about the various techniques used to compress that stream ( contrary to what most people think , TV broadcasters use coaxial cable instead of optical equipment (fiber optic) to transmit this uncompressed stream, check the cable attached to the HD cameras at Rogers center or the Air Canada Center for instance) but for us end users our reference can only be OTA that is why we sometimes refer to it as the "uncompressed" signal which we know it is not. At home there is no way for us to compare the uncompressed data stream from the HD Camera in the studio or stadium because we have no access to it. Nowadays there are professional cameras that are acctually 1920 x 1080 instead of 1440 x 1080 like the HDCAM introduced in 1997. the new HDCAM SR is acctually 1920 x 1080 at 10 bit 4:2:2 or 4:4:4 RGB with a video bitrate of 440 Mbit/s, and a total data rate of approx. 600 Mbit/s see wikipedia for more info. The equipment a network uses to produce the image also relates to the picture quality at home , usually CBS also use high quality cameras and maybe that is why sometimes the same game like the other day (White Sox vs Jays) was slightly different using SN HD or WGN HD (I was comparing side by side using the PIP with the 9242 receiver) but it all boils down to the human eye and your eye sight.

The SMTP standard allows for 3 Gb/s data rates for 1080p video resolution but there is no commercial application yet.

I gave as a present to a friend of mine my UHF yagui-based set up therefore I have no means to keep comparing OTA vs Satellite PQ. Granduncle I guess the Don Quijote in me has died lol lol lol.

Any information whether this additional compression has started? The reason I'm asking is that I'm really seeing a lot of macroblocking lately, on almost every channel. Pretty much any sports event, or a movie has it. As long as the picture is static, it looks okay, but when it comes to motion, problems begin.

I am absolutely certain that this has not been the case a few months ago. I would see it here and there, maybe while watching a hockey, or a basketball game, but now, like I said, almost every show on every channel has it.

Can this degradation of signal be a result of something else, or is it to do with the additional compression?

I am still not seeing any compression of the bit stream on the channels that were reported to be planned for compression.

I would guess that the issue is either with your STB or with the network in your neighborhood.

why aren't they used mpeg4/h.264 for compression? its a much more efficient scheme than the old mpeg-2

Because then you'd need to change out all the existing STBs which cannot do MPEG4 at a huge cost and a huge customer outcry - those with PVRs losing programming, etc..

They will be doing Switched Digital Video and moving analogue channels to digital instead.

Satellite providers have been doing just that, switching out existing set-top boxes for MPEG-4 capable ones. BEV, I believe, is doing that.

Since we're on the topic of HD and OTA, I know the max bitrate of an ATSC signal is 19Mb, but isn't the nominal rate of a single HD channel with no subchannels actually around 12Mb? ... That's the one thing I miss about my hometown, we used to get lots of OTA HD from Detroit. There's nothing like that here in Ottawa.

Still, moving the analogue channels to digital will net a good increase in and be a better use of Rogers' existing available bandwidth.

isn't the nominal rate of a single HD channel with no subchannels actually around 12Mb? No, without multicasting it tends to vary from as little as 15 to about 18+, with quite a lot of them closer to the 18 number.

Satellite providers have been doing just that, switching out existing set-top boxes for MPEG-4 capable ones. BEV, I believe, is doing that.

Bell TV offers two MPEG-4 HD boxes (one a receiver, the other a pvr). They are the same HD boxes they've had in market for 2 or 3 years, updated with MPEG-4 -- they started to issue them last fall.

It's a smart strategy to seed the market with MPEG-4 receivers (however, Bell has no MPEG-4 content). To date, Bell has not announced any "switching out existing set-top" program. At the moment, the boxes have future-proofing benefits only.

Now that Rogers is compressing, please discuss in the following thread:

http://www.digitalhome.ca/forum/showthread.php?t=104501