A Discussion On Poor SD On HDTVs

unkster · 01-10-2005, 07:42 PM

Excellent Article!! I have a 50" RCA DLP with off air antenna for my HD network locals and Dish 811 reciever. The local network stations through the antenna are noticably better in SD than the Dish signal. Since I am recieving a "pure" signal without the compression I would guess that would be the reason. Hope I explained that right. And you are correct about changing the settings for watching SD. I have played around with the settings to where I have a very good to excellent picture on the SD satellite stations,, although some of the channels are better than others. It seems that the older taped shows have the worse PQ.

theCableGuy · 01-11-2005, 03:01 PM

rbnick......I wish I had one hundred thousand customers like you in my system. I've been fighting for the past 2 years to get people to understand why switching inputs is the best thing they can do for picture quality of our analog and digital channels! The biggest fight I get is most subscribers don't like switching inputs. Thank you for educating the few select people that have enough presence of mind to read HD forums, which I cruise looking for information I can use and more importantly, see what issues people are bringing to the table. Most excellent write up and I look forward to seeing what the rest of this HD forum has to offer.

**rbinck** · 01-11-2005, 03:34 PM

Thanks CableGuy,

Hopefully you will find some gems here. Maybe add a few yourself.

sel · 02-25-2005, 04:21 PM

Ok, so HDTVs don"t do SD very well. Would you venture a recommendation of a large screen tv (40-50 inches) for someone who is not technically adept , wants a tv that will no go out of date in a couple of years (CRT??) and is somewhat price sensitive (one can't claim to be too price sensitive if one is purchasing a tv of this category). With up to 15 feet of viewing distance, what type and what model (brand and model) would you recommend. Should it be a Samsung LCD, a Toshiba DLP, a Song CRT -- or what?

fernando_g · 03-09-2005, 07:44 AM

Quote:

Originally Posted by Forge

What does NTSC tuner stand for?

Never Twice the Same Color

of course, the Germans decided to improve NTSC, and came up with the better but costlier PAL system, Pay for the Added Luxury.

and the French, in a typical French fashion came up with a version of their own, and since the logical color encoding schemes had already been done by the Americans and improved upon by the Germans, they came with SECAM, System Essentially Contrary to the American Method.

Now you know..........

fryet · 03-14-2005, 04:05 PM

Are certain screens better than others when switching between resolutions? I would assume that a CRT with flexibile pixel size would do a better job than a LCD would with fixed pixel size. Is the difference significant? Would a HDTV ever play an analog SD signal or DVD signal worse than what you would get on a non-HDTV?

When it comes to my future planned usage of a HDTV, here is how things currently stack:

#1 - DVD
#2 - broadcast SD
#3 - HD DVD
#4 - VHS
#5 - broadcast HD (will vary between 720p and 1080i, I imagine)

I definitely want #3 to be in great quality, so I plan to get a 1080p system, however I want to make sure that #1, #2, and #4 play at least as well as my current TV. As for #5, I certainly expect 720p to be better than anything I would see on SD, but if I am wrong in that assumption, please do let me know!)

**rbinck** · 03-14-2005, 05:00 PM

I don't know about the CRTs being better than LCDs. Rear Projection CRTs that don't have a shadow mask fit your description, but direct view CRTs will have their pixel sizes set somewhat by the shadow masks or vertical masks in the case of Sony.

If you are going to get a 1080p display, you will not be getting a CRT anyway.

The issue with poor SD is one of the sources. Digital sources such as cable and satellite have decompresstion artifacts that are magnified by the HDTVs. Some receivers handle them better than others and is worth trying to get a look at SD if possible before buying the TV or the source box. Here is an example of a decompression artifact:

The example on the left shows what is the most common decompression artifact. The other disappointment will be once you watch much HD it is hard to go back to SD.

fryet · 03-14-2005, 06:00 PM

OK, so if I have a 1080p HDTV, it doesn't matter if it is rear-projection, LCD, plasma, CRT, etc. I won't have problems switching between SD, DVD, 720p, 1080i, and 1080p based on the type of technology. If I do have poor picture quality, it is due to the signal source only.

**rbinck** · 03-14-2005, 07:59 PM

Pretty much the source, yes. They can't make detail out of nothing cheaply enough to allow the TVs of today clean up the pictures that need to be expanded by a factor of x2 each direction. Sort of like blowing up a picture on the computer. There are very expensive pieces of equipment to "fill in" detail, but are way beyond the cost of consumer electronics.

Then the decompression artifacts can only be delt with at the time of decompression, if at all. Once the receiver hands it off to your TV, there is little the TV can do to clean up the picture. That is why in many cases the analog signal from OTA or cable will look better than the output of a satellite receiver or digital cable box. The TV is better equipped to scale an analog signal than it is able to deal with an analog or digital signal that contains decompression artifacts.

RSawdey · 03-19-2005, 02:51 PM

All ATSC formats can be upconverted to 1080p/60 without data loss. All info from the lesser format is retained, but you've only got what comes in the package. No dropped frames or interlacing artifacts inserted, but 480i is still going to look more 'soft' than 1080i when presented, and 1080i will look more 'blurry' than 720p with motion, even after upconversion to 1080p60. I'm sure the upconverter will do a fine job, but it can't invent detail, just preserve what it's got & smooth over the scaling in the spatial or temporal axes.

The time for dealing with compression artifacts is at the time of compression. Compressors use different algorythms for compressing different scenes, depending on which gives the best compression ratio... but a human operator can override this method choice to produce a better looking result even if it means a few more bits in the stream. Problems arise when the compressed stream must fit in a certain bandwidth, so it has a limited bitrate. Now it's a question of what aspect of the image do you compromise to fit into what room you've got in the channel. Color res, spatial res, framerate? Being a good operator isn't an easy job... and the automatic choices used with real-time auto compression aren't that smart. This problem of channel saturation is more of an issue with 1080i than 720p, since 1080i is trying to push about 10% more pixels per second thru the same sized pipe... 720p has a little more 'elbow room' for those scenes that take more than average bits to show well.

**rbinck** · 03-20-2005, 01:32 PM

Actually it will not be long before we begin to see some of the advances in digital video processing showing up in consumer electronics. For example, here is a text on the technology to "fill in" detail:
Temporal resolution enhancement in compressed video sequences

The link requires Acrobat Reader as it is a pdf, but it is a very interesting look at things to come.

In a session with a projector company the other day we were discussing the current level of video processing for consumers compared to what is being developed. In addition to the temporal resolution (quantity of frames/sec) enhancement which will truly allow 24 fps to be converted to 30fps with 6 "developed" frames, or 60 fps they think ultimately, they also are working on simular processing to improve the spatical resolution (quantity of pixels per frame) as well. As soon as these formulas can be placed on chips, the new products can start to emerge. None of this was practicable with analog processing!

Tommorow looks like it could be a great day.

RSawdey · 03-20-2005, 04:39 PM

Very cool stuff, kinda like the 'tweening' Disney uses to smooth the motion of hand drawn animation by calculating the frames 'between' the drawn ones... nice to note the author says it can be implimented with the H.263 codec (MPEG4 part 10). Sure a big improvement on 3:2 pulldown, which just repeats frames unmodified.

cracker · 04-08-2005, 02:55 PM

bear with me, i'm new at this...basically if I have digital cable I should just split the coax behind the TV and run one line straight into the TV for SD viewing and run the other end thru the converter box and down to the TV for HD viewing?

RSawdey · 04-08-2005, 06:05 PM

That will depend on what kind of TV you have, what kind of tuner it has built in, and quality of the SD over the same connection as HDTV.

TucsonJoel · 04-08-2005, 08:55 PM

Just switched from Comcast cable (with HD/DVR receiver via component inputs) to Dish DVR twin tuner 522 - the promise of all digital you know - being as good as my cable's HD; I have a 52" rear projection HDTV - what have I done! I can't stand the picture quality; the Dish SD is much worse than my cable SD; it looks like VCD quaity. Is there any hope here? I can't stand to watch it.

01-10-2005, 07:42 PM	#16
unkster You Can Never Go Back Join Date: Aug 2004 Location: Hudson Valley Area,NY Posts: 236	SD on HDTV Excellent Article!! I have a 50" RCA DLP with off air antenna for my HD network locals and Dish 811 reciever. The local network stations through the antenna are noticably better in SD than the Dish signal. Since I am recieving a "pure" signal without the compression I would guess that would be the reason. Hope I explained that right. And you are correct about changing the settings for watching SD. I have played around with the settings to where I have a very good to excellent picture on the SD satellite stations,, although some of the channels are better than others. It seems that the older taped shows have the worse PQ. Last edited by unkster; 01-10-2005 at 07:44 PM. Reason: add

01-11-2005, 03:01 PM	#17
theCableGuy High Definition is the definition of life. Join Date: Jan 2005 Posts: 172	RE: poor SD rbnick......I wish I had one hundred thousand customers like you in my system. I've been fighting for the past 2 years to get people to understand why switching inputs is the best thing they can do for picture quality of our analog and digital channels! The biggest fight I get is most subscribers don't like switching inputs. Thank you for educating the few select people that have enough presence of mind to read HD forums, which I cruise looking for information I can use and more importantly, see what issues people are bringing to the table. Most excellent write up and I look forward to seeing what the rest of this HD forum has to offer.

03-14-2005, 04:05 PM	#21
fryet High Definition is the definition of life. Join Date: Mar 2005 Location: Bay Area, CA Age: 38 Posts: 632	So does the HDTV you choose affect things at all? Are certain screens better than others when switching between resolutions? I would assume that a CRT with flexibile pixel size would do a better job than a LCD would with fixed pixel size. Is the difference significant? Would a HDTV ever play an analog SD signal or DVD signal worse than what you would get on a non-HDTV? When it comes to my future planned usage of a HDTV, here is how things currently stack: #1 - DVD #2 - broadcast SD #3 - HD DVD #4 - VHS #5 - broadcast HD (will vary between 720p and 1080i, I imagine) I definitely want #3 to be in great quality, so I plan to get a 1080p system, however I want to make sure that #1, #2, and #4 play at least as well as my current TV. As for #5, I certainly expect 720p to be better than anything I would see on SD, but if I am wrong in that assumption, please do let me know!)

03-14-2005, 06:00 PM	#23
fryet High Definition is the definition of life. Join Date: Mar 2005 Location: Bay Area, CA Age: 38 Posts: 632	Thanks OK, so if I have a 1080p HDTV, it doesn't matter if it is rear-projection, LCD, plasma, CRT, etc. I won't have problems switching between SD, DVD, 720p, 1080i, and 1080p based on the type of technology. If I do have poor picture quality, it is due to the signal source only.

01-11-2005, 03:34 PM	#18
rbinck Administrator Join Date: Apr 2004 Location: Katy, Texas Posts: 12,301	Thanks CableGuy, Hopefully you will find some gems here. Maybe add a few yourself.

02-25-2005, 04:21 PM	#19
sel A couch and an HDTV to go please. Join Date: Aug 2004 Location: Los Angeles Posts: 12	Ok, so HDTVs don"t do SD very well. Would you venture a recommendation of a large screen tv (40-50 inches) for someone who is not technically adept , wants a tv that will no go out of date in a couple of years (CRT??) and is somewhat price sensitive (one can't claim to be too price sensitive if one is purchasing a tv of this category). With up to 15 feet of viewing distance, what type and what model (brand and model) would you recommend. Should it be a Samsung LCD, a Toshiba DLP, a Song CRT -- or what?

03-14-2005, 05:00 PM	#22
rbinck Administrator Join Date: Apr 2004 Location: Katy, Texas Posts: 12,301	I don't know about the CRTs being better than LCDs. Rear Projection CRTs that don't have a shadow mask fit your description, but direct view CRTs will have their pixel sizes set somewhat by the shadow masks or vertical masks in the case of Sony. If you are going to get a 1080p display, you will not be getting a CRT anyway. The issue with poor SD is one of the sources. Digital sources such as cable and satellite have decompresstion artifacts that are magnified by the HDTVs. Some receivers handle them better than others and is worth trying to get a look at SD if possible before buying the TV or the source box. Here is an example of a decompression artifact: The example on the left shows what is the most common decompression artifact. The other disappointment will be once you watch much HD it is hard to go back to SD.

03-14-2005, 07:59 PM	#24
rbinck Administrator Join Date: Apr 2004 Location: Katy, Texas Posts: 12,301	Pretty much the source, yes. They can't make detail out of nothing cheaply enough to allow the TVs of today clean up the pictures that need to be expanded by a factor of x2 each direction. Sort of like blowing up a picture on the computer. There are very expensive pieces of equipment to "fill in" detail, but are way beyond the cost of consumer electronics. Then the decompression artifacts can only be delt with at the time of decompression, if at all. Once the receiver hands it off to your TV, there is little the TV can do to clean up the picture. That is why in many cases the analog signal from OTA or cable will look better than the output of a satellite receiver or digital cable box. The TV is better equipped to scale an analog signal than it is able to deal with an analog or digital signal that contains decompression artifacts.

03-19-2005, 02:51 PM	#25
RSawdey Mr. Wizard Join Date: Feb 2005 Location: Ferndale, Michigan Age: 61 Posts: 5,981	All ATSC formats can be upconverted to 1080p/60 without data loss. All info from the lesser format is retained, but you've only got what comes in the package. No dropped frames or interlacing artifacts inserted, but 480i is still going to look more 'soft' than 1080i when presented, and 1080i will look more 'blurry' than 720p with motion, even after upconversion to 1080p60. I'm sure the upconverter will do a fine job, but it can't invent detail, just preserve what it's got & smooth over the scaling in the spatial or temporal axes. The time for dealing with compression artifacts is at the time of compression. Compressors use different algorythms for compressing different scenes, depending on which gives the best compression ratio... but a human operator can override this method choice to produce a better looking result even if it means a few more bits in the stream. Problems arise when the compressed stream must fit in a certain bandwidth, so it has a limited bitrate. Now it's a question of what aspect of the image do you compromise to fit into what room you've got in the channel. Color res, spatial res, framerate? Being a good operator isn't an easy job... and the automatic choices used with real-time auto compression aren't that smart. This problem of channel saturation is more of an issue with 1080i than 720p, since 1080i is trying to push about 10% more pixels per second thru the same sized pipe... 720p has a little more 'elbow room' for those scenes that take more than average bits to show well.

03-20-2005, 01:32 PM	#26
rbinck Administrator Join Date: Apr 2004 Location: Katy, Texas Posts: 12,301	Actually it will not be long before we begin to see some of the advances in digital video processing showing up in consumer electronics. For example, here is a text on the technology to "fill in" detail: Temporal resolution enhancement in compressed video sequences The link requires Acrobat Reader as it is a pdf, but it is a very interesting look at things to come. In a session with a projector company the other day we were discussing the current level of video processing for consumers compared to what is being developed. In addition to the temporal resolution (quantity of frames/sec) enhancement which will truly allow 24 fps to be converted to 30fps with 6 "developed" frames, or 60 fps they think ultimately, they also are working on simular processing to improve the spatical resolution (quantity of pixels per frame) as well. As soon as these formulas can be placed on chips, the new products can start to emerge. None of this was practicable with analog processing! Tommorow looks like it could be a great day.

03-20-2005, 04:39 PM	#27
RSawdey Mr. Wizard Join Date: Feb 2005 Location: Ferndale, Michigan Age: 61 Posts: 5,981	Very cool stuff, kinda like the 'tweening' Disney uses to smooth the motion of hand drawn animation by calculating the frames 'between' the drawn ones... nice to note the author says it can be implimented with the H.263 codec (MPEG4 part 10). Sure a big improvement on 3:2 pulldown, which just repeats frames unmodified.

04-08-2005, 02:55 PM	#28
cracker HD noob Join Date: Apr 2005 Location: Houston Posts: 1	bear with me, i'm new at this...basically if I have digital cable I should just split the coax behind the TV and run one line straight into the TV for SD viewing and run the other end thru the converter box and down to the TV for HD viewing?

04-08-2005, 06:05 PM	#29
RSawdey Mr. Wizard Join Date: Feb 2005 Location: Ferndale, Michigan Age: 61 Posts: 5,981	That will depend on what kind of TV you have, what kind of tuner it has built in, and quality of the SD over the same connection as HDTV.

04-08-2005, 08:55 PM	#30
TucsonJoel What is HD? Join Date: Apr 2005 Posts: 3	Just switched from Comcast cable (with HD/DVR receiver via component inputs) to Dish DVR twin tuner 522 - the promise of all digital you know - being as good as my cable's HD; I have a 52" rear projection HDTV - what have I done! I can't stand the picture quality; the Dish SD is much worse than my cable SD; it looks like VCD quaity. Is there any hope here? I can't stand to watch it.