or Connect
AVS › AVS Forum › Display Devices › Flat Panels General and OLED Technology › TV Signal Compression In The Real World
New Posts  All Forums:Forum Nav:

TV Signal Compression In The Real World

post #1 of 270
Thread Starter 
Is the degree of compression regarding TV signals the same when a show is broadcast at 7PM then re-broadcast at 10PM? What component inside the TV takes a poor (overly compressed) signal and makes it better? Video Processor, or a combination of components? Is the amount of compression dictated by the provider alone (Directv, Dish, Comcast, etc)? MEG4 has replaced MEG2. Is there anything better on the horizon?
post #2 of 270
In my experience rebroadcasts are the same as the original broadcast.

Some sets are more forgiving of overcompression than others. Where I work we have a store feed and one Dish HD box that's about 3 years old. I've seen about 7 or 8 different sets in the 60" range from various mfgs connected to it. The most forgiving have all been plasmas because they have an inherently slightly softer picture than lcds, not because of any video processing.

Compression is done at every step in the chain from network to local station to cable/sat system. Most variable is the compression done by cable/sat companies. For cable the amount of compression can vary from system to system depending on the local market--i.e. Comcast may apply more compression to a given channel in one city vs another. Satellite systems are consistent as far as nationwide channels like ESPN but can vary for locals. DirecTV is better than Dish for nationwide channels in my experience with the store box vs DirecTV boxes I have at home.

Overall compression is much worse now than it was 10 years ago when there were far fewer HD channels crammed on to the cable/sat systems.
post #3 of 270
Thread Starter 
Quote:
Originally Posted by Steve S View Post

In my experience rebroadcasts are the same as the original broadcast.

Some sets are more forgiving of overcompression than others. Where I work we have a store feed and one Dish HD box that's about 3 years old. I've seen about 7 or 8 different sets in the 60" range from various mfgs connected to it. The most forgiving have all been plasmas because they have an inherently slightly softer picture than lcds, not because of any video processing.

Compression is done at every step in the chain from network to local station to cable/sat system. Most variable is the compression done by cable/sat companies. For cable the amount of compression can vary from system to system depending on the local market--i.e. Comcast may apply more compression to a given channel in one city vs another. Satellite systems are consistent as far as nationwide channels like ESPN but can vary for locals. DirecTV is better than Dish for nationwide channels in my experience with the store box vs DirecTV boxes I have at home.

Overall compression is much worse now than it was 10 years ago when there were far fewer HD channels crammed on to the cable/sat systems.
Thanks Steve. Could you compare MEG 2 and MEG 4? What component differences were at play with say the Sharp Elite that allowed it to deliver a higher level of PQ for regular TV broadcasts as well as dvd and blu-ray then most other LED/LCD's?
post #4 of 270
Quote:
Originally Posted by andy sullivan View Post

Thanks Steve. Could you compare MEG 2 and MEG 4? What component differences were at play with say the Sharp Elite that allowed it to deliver a higher level of PQ for regular TV broadcasts as well as dvd and blu-ray then most other LED/LCD's?


Basically, MPEG 2 files can usually offer better quality then MPEG 4 but they require more bandwidth.

http://www.differencebetween.net/technology/difference-between-mpeg2-and-mpeg4/


According to the ISF ( Image Science Foundation) the most important aspect of picture quality, from any TV LCD or Plasma, is contrast ratio, the second most important is color saturation, and the third is color accuracy. Resolution comes in fourth, (despite being the most-cited HDTV specification).


Ian
Edited by mailiang - 7/10/13 at 11:49am
post #5 of 270
Quote:
Originally Posted by mailiang View Post

Basically, MPEG 2 files can usually offer better quality then MPEG 4 but they require more bandwidth.

http://www.differencebetween.net/technology/difference-between-mpeg2-and-mpeg4/
I don't think that link is really accurate. eg. "MPEG4 simply discards more information, which results in poorer picture." - it's not that mpeg4 just discards more information, the broadcaster/encoders will decide what bitrates to use. A better comparison would be - "at a particular bitrate which codec gives the best picture quality?". Since AVC/mpeg4 is currently the codec used on the vast majority of Blu-ray titles, AVC/mpeg4 looks like it's the best, otherwise they'd be using mpeg2.

They're using mpeg4/avc because at the same bitrate it can usually give better results, or at a lower bitrate than mpeg2 give an equivalent picture. Though the higher bitrate you go (eg. over 40 mbps?) the less of a difference between the two there will be.
Edited by Joe Bloggs - 7/10/13 at 10:25pm
post #6 of 270
Thread Starter 
So are there internal components designed to compensate for compressions negative effect on PQ? I mentioned the Sharp Elite in an earlier post. Most professional reviewers were impressed with that sets overall PQ which I assume was part of the reason it was so expensive, and no longer produced. If you were going to build the ultimate LED/LCD with no local dimming where would you spend your money? Same scenario with cost being a medium but not bottom line factor?
post #7 of 270
Quote:
Originally Posted by andy sullivan View Post

So are there internal components designed to compensate for compressions negative effect on PQ? I mentioned the Sharp Elite in an earlier post. Most professional reviewers were impressed with that sets overall PQ which I assume was part of the reason it was so expensive, and no longer produced. If you were going to build the ultimate LED/LCD with no local dimming where would you spend your money? Same scenario with cost being a medium but not bottom line factor?
Not unless the time-space continuum has been violated. The only true way to correct for a lossy compression is to put the removed data back. Or are you asking if lossy compression can be successfully hidden? That depends on the content and the viewer.
post #8 of 270
Pro reviewers base their judgements on the best possible signal source, which as far as compression goes is Blu Ray disc for us mortals. The old axiom "garbage in=garbage out" is the rule of thumb. I laugh inwardly when I see debates over whether the Dish Hopper is better than the DirecTV Genie--the plain fact is that in my experience Dish's overcompression with it's resultant macroblocking and clayface effect is a heckuva a lot more important than any advantage one box may have with menu navigation or whatever.

Plasma's slightly softer picture hides compression problems better than lcd, and the compression problems are more visible the larger the screen size. Other than that a tv can't do anything to fix overcompression artifacting. Our dish box at work looks better on a cheap $899 60" plasma than on a $3200 60" Samsung F8000 premium LED/LCD.
post #9 of 270
Quote:
Originally Posted by andy sullivan View Post

MEG4 has replaced MEG2. Is there anything better on the horizon?

Yes, HEVC

http://en.wikipedia.org/wiki/HEVC
post #10 of 270
Quote:
Originally Posted by andy sullivan View Post

So are there internal components designed to compensate for compressions negative effect on PQ?
There could be certain digital filters/algorithms that they use to try to mask any picture problems/improve on the picture. Eg. digital noise reduction. Some could use better algorithms, including for things like scaling, than other TVs. Though digital NR on TVs can usually be turned off. Though it's still possible that different TVs could output the same content differently by using different digital processing.
post #11 of 270
I am quite disappointed with the quality of broadcasts, at least locally. I think a big problem is the local stations, which seem to decode the signal, then add in their advertisements and promo's then re-encode with cheap or old equipment. I've seen reasonable quality of a show on one station, then really poor quality on another station 2 hrs later. Sometimes the problem is a really soft re-encode, other times bad macroblocking (depending on which local we're talking about). I find the quality poor enough and the promo's/ads/logos annoying enough that I'm considering dropping cable and just downloading the web broadcasts instead. I'm also considering just not watching the show until it is released on blu-ray and the price is reasonable, which may force me to wait 2 years after the show actually airs. Obviously some series never seem to release on BD, so I'd have to settle for 1080p web DL's. The only reason I haven't dropped cable yet is some games I can only get via cable because none of the OTA stations carry it.

All of which might seem a bit off topic, but I think a lot of the problem is cheap local stations with substandard equipment. No TV can correct it, and large high quality TV's are more likely to expose the problem, not cover it up. Unless you "dumb down" your expensive TV. In which case, why bother. So you end up buying the TV for blu-ray and settling on the broadcast quality at other times.

As a little aside. I'm kind of a hi-def ho. I just can't watch much SD stuff anymore. I recorded a couple of movies which haven't been release in HD yet (The Replacements comes to mind) and was going to encode and save them to replace my dvd. But the extra detail in the image due to higher resolution just couldn't offset the macro-blocking, blown out contrast etc. and I just wound up trashing the recording. So much for broadcast quality smile.gif
post #12 of 270
It has come to the point where Internet-based streams (even Netflix!) have routinely exceeded the picture quality of common cable/satellite providers.

As Internet streams continue to improve in quality, it'll hopefully scare the providers into improving the over-compression situation.

Also, compression has another side problem: It can add additional unwanted motion blur -- it greatly hurts motion clarity in sports, etc.
post #13 of 270
Quote:
Originally Posted by Mark Rejhon 

Also, compression has another side problem: It can add additional unwanted motion blur -- it greatly hurts motion clarity in sports, etc.
TV noise reduction also adds motion blur smile.gif
post #14 of 270
Quote:
Originally Posted by 8mile13 View Post

TV noise reduction also adds motion blur smile.gif
not just blur?
post #15 of 270
Quote:
Originally Posted by Mark Rejhon View Post

It has come to the point where Internet-based streams (even Netflix!) have routinely exceeded the picture quality of common cable/satellite providers.

As Internet streams continue to improve in quality, it'll hopefully scare the providers into improving the over-compression situation.

The main reason Netflix and similar services will look better is because those streams are pre-encoded with non-real-time multi-pass encoders. It's also primarily 24 fps film content vs. the 29.97i or 59.94p used in broadcasting. If Netflix was streaming live network programming, it would look like garbage - even compared to cable/satellite. For evidence, see AT&T Uverse live-tv streaming service.

Most likely, satellite will transition to HEVC as soon as hardware becomes widely available. Cable tends to be slower to adopt new codecs because the larger installed base makes end-user hardware upgrades more difficult and expensive.
Edited by Wizziwig - 7/31/13 at 1:48am
post #16 of 270
Yea when I watch netflix and switch back to uverse its always a disappointment. In fact, I am borderline ready to cancel my cable. I hardly ever watch it now that internet tv has really taken off.
post #17 of 270
Quote:
Originally Posted by Joe Bloggs View Post

Quote:
Originally Posted by 8mile13 View Post

TV noise reduction also adds motion blur smile.gif
not just blur?
When NR is set to high picture is softer and blur in motion is more apparent.
post #18 of 270
Quote:
Originally Posted by 8mile13 View Post

When NR is set to high picture is softer and blur in motion is more apparent.
But since it isn't specific to things in motion, it isn't really motion blur, but instead is just blur, since everything is blurred irrespective of whether it's in motion or not.
post #19 of 270
I have FIOS and on my Panasonic 60ST60 it looks great. Way better than Netflix.

Compression typically doesn't effect the resolution of the image, it typically effects the available color palette. It will replace colors that are within a range with a single color and the result is banding. Most often seen when there are dark backgrounds.
post #20 of 270
It depends whether it's spatial or temporal noise reduction. These days the lower levels are normally spatial noise reduction, and higher levels of noise reduction introduce temporal noise reduction, which adds motion blur.
There are also other kinds of noise reduction such as "MPEG noise reduction" which tries to reduce the appearance of macroblocking.

If it is carefully controlled during the mastering process, noise reduction can be a useful tool. I regularly use noise reduction - and sometimes even add noise after the fact when editing photographs.
But anything built into a television or video processor is generally awful, and really hurts image quality.
post #21 of 270
Quote:
Originally Posted by Joe Bloggs View Post

Quote:
Originally Posted by 8mile13 View Post

When NR is set to high picture is softer and blur in motion is more apparent.
But since it isn't specific to things in motion, it isn't really motion blur, but instead is just blur, since everything is blurred irrespective of whether it's in motion or not.

My XBR8 will lose very little of its sharpness when mpeg NR is set to low though when there is motion there is an increase in blur. When mpeg NR is set to mid picture becomes somewhat softer and blur in motion increases to a degree that it becomes annoying. So on my TV there is mpeg NR related blur when there is motion and NO mpeg NR related blur when there is no motion.
post #22 of 270
Thread Starter 
What does a video processor like the Darbee Darblet ( or somebody else's) do for motion or is it strictly a sharpness device?
post #23 of 270
Quote:
Originally Posted by 8mile13 View Post

Quote:
Originally Posted by Joe Bloggs View Post

Quote:
Originally Posted by 8mile13 View Post

When NR is set to high picture is softer and blur in motion is more apparent.
But since it isn't specific to things in motion, it isn't really motion blur, but instead is just blur, since everything is blurred irrespective of whether it's in motion or not.

My XBR8 will lose very little of its sharpness when MPEG NR is set to low though when there is motion there is an increase in blur. When MPEG NR is set to mid picture becomes somewhat softer and blur in motion increases to a degree that it becomes annoying. So on my TV there is MPEG NR related blur when there is motion and NO MPEG NR related blur when there is no motion.

I was describing how Sony MPEG Noise Reduction affects my TV . I use the Noise Reduction LOW option when watching Satellite TV. A reviewer advised to use the HIGH setting but there was to much blur (when there was motion) so i stick with LOW.
post #24 of 270
Does anyone know why the U.S. cable/satellite providers still use MPEG2 and most other countries such as Europe use H.264? Is it a matter of no competition in the U.S. so no pressure to upgrade their systems or did Europe skip MPEG2 and go straight to H.264 from the beginning? I find that the H.264 broadcasts look much better, no macroblocking on 1080i like you get with MPEG2.
post #25 of 270
Quote:
Originally Posted by StinDaWg View Post

Does anyone know why the U.S. cable/satellite providers still use MPEG2 and most other countries such as Europe use H.264? Is it a matter of no competition in the U.S. so no pressure to upgrade their systems or did Europe skip MPEG2 and go straight to H.264 from the beginning? I find that the H.264 broadcasts look much better, no macroblocking on 1080i like you get with MPEG2.
Quite a few providers use H.264. VOD has always used H.264, IPTV providers use it, so do various Satellite providers.
post #26 of 270
Quote:
Originally Posted by gregzoll View Post

Quite a few providers use H.264. VOD has always used H.264, IPTV providers use it, so do various Satellite providers.
That's simply not true. Every major U.S. cable provider I know of does MPEG2 for their standard HDTV broadcasts. VOD for Time Warner uses MPEG2, not H.264.
post #27 of 270
Quote:
Originally Posted by StinDaWg View Post

...or did Europe skip MPEG2 and go straight to H.264 from the beginning?.
Europe still uses mpeg2 for standard definition channels on terrestrial broadcasts. But went more or less straight to H264 for high definition broadcasts. Though internally their connections/some of them may still be using high bitrate mpeg2.
Edited by Joe Bloggs - 8/5/13 at 3:41am
post #28 of 270
Quote:
Originally Posted by Joe Bloggs View Post

Europe still uses mpeg2 for standard definition channels on terrestrial broadcasts. But went more or less straight to H264 for high definition broadcasts. Though internally their connections/some of them may still be using high bitrate mpeg2.

Even this is bit too generalizing. Those who switched late to terrestrial digital in Europe now use H.264 for standard definition TV over terrestrial. In turn those who were first to switch to digital and use MPEG-2 are now in the process of introducing new DVB-T2 terrestrial which has advanced modulation enabling 5 HD programs compressed with H.264 in a single TV channel. But the transition is slowed by consumers tired of those changes.
post #29 of 270
Quote:
Originally Posted by irkuck View Post

Even this is bit too generalizing. Those who switched late to terrestrial digital in Europe now use H.264 for standard definition TV over terrestrial. In turn those who were first to switch to digital and use MPEG-2 are now in the process of introducing new DVB-T2 terrestrial which has advanced modulation enabling 5 HD programs compressed with H.264 in a single TV channel. But the transition is slowed by consumers tired of those changes.
Yes, the UK use DVB-T2 and H264 for terrestrial broadcasting of the high definition channels (with more HD channels coming soon) - but no SD channels are broadcast on it.
The SD channels in the UK still broadcast terrestrially on DVB-T using MPEG2.

A problem with changing is lots of equipment becoming obsolete and people having to spend £ to replace them.

Another change will be to to H265 and UHDTV whenever that will be.
Edited by Joe Bloggs - 8/5/13 at 5:37am
post #30 of 270
Quote:
Originally Posted by StinDaWg View Post

That's simply not true. Every major U.S. cable provider I know of does MPEG2 for their standard HDTV broadcasts. VOD for Time Warner uses MPEG2, not H.264.
When it comes from the servers, it is H.264, then the provider may change it to MPEG, but the stream is still H.264. BTW, isn't Time Warner putting themselves out of business at this point? Not a good example.
New Posts  All Forums:Forum Nav:
  Return Home
AVS › AVS Forum › Display Devices › Flat Panels General and OLED Technology › TV Signal Compression In The Real World