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Author Topic: HDTV/ DVD/ SDTV Question Larry Myers Master Film Handler Posts: 371 From: Herndon, VA, USA Registered: Jan 2001 posted 03-15-2005 06:45 PM                 Hi Why is it that at least with my system, DVD's plays better (higher resolution and detail) then the standard Comcast cable TV but not as good as Comcast HDTV? It seems to me that DVD's should play about the same as Cable TV but it really plays right in the middle of standard TV and HDTV in resolution. Larry  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 03-15-2005 07:59 PM                        Well since I refuse to pay for television programming that has commercials in it, I obviously don't have something as wallet-sucking as cable so I can only speculate on the answers: #1 - Cable TV quality always sucks ass. If you get a good picture, then something is definitely wrong. Yet another reason not to actually pay for TV. Even digital cable is all compressed to hell. Oh well, it's your money not mine. I am laughing at you, though... paying for TV. HA! Also, SD video tends to look like ass when viewed on an HD set, as HDTV's just can't handle it as it was meant to be handled (they are nowhere near as versatile as computer monitors). #2 - DVDs are higher resolution than your standard broadcast signal. DVDs are typically 720x480 which is waaay above what SD broadcasts are usually at in terms of overall discernable pixels. Also DVDs don't have to go through a crappy coaxial wire for hundreds of feet. Instead it is hooked up right there with component cables. Next, DVDs play back in 480p, which helps it to look a bit nicer as well. You do have your DVD player hooked up for progressive scan, right? #3 - HDTV is either 1280x720 or 1920x1080 (interlaced... for now) for the resolution. This signal gets squashed down to a crappy 19mbps (or less) MPEG2 signal and sent you your home. MPEG2 is also used in DVD at a little less than half that bit rate (usually). MPEG2 is an awful codec, one of the worst ever created with TONS of visable arifacts (all of which are completely unacceptable). That's why whenever anything moves fast on HDTV programs, the entire screen turns into a pixelated mess. Whoever invented MPEG2 should be shot along with their parents and children. Much more efficient and higher quality codecs will be used for the new DVD formats coming up. And there is talk of changing over HDTV broadcasts to the better codecs as well. Of course that will render all current HDTV sets obsolete but you don't mind buying a new "set top box" right?  |  IP: Logged Larry Myers Master Film Handler Posts: 371 From: Herndon, VA, USA Registered: Jan 2001 posted 03-15-2005 09:36 PM                 Hi Comcast standard is included in the rent so I more or less get it for free. The Panasonic TAU HDTV set has only one component hookup so the DVD player is S video and 480I play. The HDTV out of Comcast is componet 720p. The DVD player is also hooked up to a Sony decoder surround sound by coaxial and Comcast is hooked up to an optical cable for surround sound. The Comcast HDTV is, I think, very good. The DVD also looks very good even though it's S video. The standard programing is just so-so. You would think 480i is 480i but the DVD's are playing way better then standard programming. Larry  |  IP: Logged Evans A Criswell Phenomenal Film Handler Posts: 1579 From: Huntsville, AL, USA Registered: Mar 2000 posted 03-22-2005 04:05 PM                        Technical answer: because DVD has better resulution than cable TV, but not nearly as much as HDTV. Take a look at the NTSC broadcast parameters: Luma Bandwidth: 4.2 MHz Color Carrier: 3.57954545 MHz (315 over 88) Frame rate: 29.97 frames/sec Field rate: 59.94 fields/sec Scan lines per frame: 525 Visible Scan lines: 483 (now considered to be 480 in the digital age) Percent of scan line used for picture: 0.8322 percent (52 8/9 over 63 5/9) Bandwidth per scan line: 222.1 Hz Lines of resolution (luma, broadcast) per picture width: 444.3 Lines of resolution (luma, broadcast) per 4:3 picture height: 333.2 Lines of resolution (luma, broadcast) per screen width per MHz bandwidth: 105.8 "TV Lines" per MHz (above figure multiplied by reciprocal of aspect ratio 4:3): 79.34 Lines of resolution (chroma, broadcast) per screen width: 63.5 Pixel resolution needed to capture luma (broadcast): 635 width, 480 height Color bandwidth (1.3 MHz equiband in studio, 600 KHz equiband broadcast for I and Q (1.3MHz wideband-I abandoned long ago)) So, the luminance is 4.2 MHz, although when color was introduced, some of the high frequencies were sacrificed to include the color information. Now much of the high frequency luminance remains after the color information is separated depends on how sophisticated the comb filter is. Many cheap devices simply extract the luminance below 3 MHz and don't bother trying to uninterleave the luma and color frequencies in the upper region. Multiply bandwidth in MHz by 105.8 to get the number of lines of resolution horizontally, so 3 MHz limits you to 317.4 . Luminance resolution above that is corrupted at least partially by the insertion of the color, centered at 3.58 MHz. A lot of it is recoverable if the interleaving is done properly in the composite signal, though. The limiting resolution for luminance per screen width is 444, of course with some corruption between 317.4 and 444 because of the color information. A DVD, if you hook it up with component cables, gets around the frequency interleaving of the luma and chroma. Using the commonly accepted Kell value of 0.7, the 720 pixels of DVD is roughly equivalent to 4.76 MHz luminance (504 lines of resolution across the picture). That's about 13.4 percent better than a full-bandwidth 4.2 MHz broadcast signal as far as luminance goes, but, there's no corruption of the upper luminance frequencies, other than compression artifacts. Where DVD shines is the color bandwidth. Broadcast TV uses equiband 0.6 bandwidth components (although the I component was originally supposed to be 1.3 or 1.5 MHz, but was mostly abandoned), which limits the color resolution to 63.5 lines of resolution. The eye is not as sensitive to this limitation as it is to the luminance, which is 4.2 MHz. The color resolution horizontally is one seventh of the luminance. DVD has a color resolution of 360 by 240, which is equivalent to 2.38 MHz compared to the 0.6 of broadcast TV. That's 252.0 color lines of resolution horizontally compared to 63.5 color lines of resolution of broadcast TV. The only bad thing about DVD is it only has half the vertical color resolution of broadcast TV. I can really notice that now when I watch some DVDs. But, even taking this into account, DVD still beats broadcast by a long way, plus the fact that the color and luminance don't interfere with each other with DVD. If you use a composite cable, you are going back to some of the broadcast limitations with mixing of the luminance and color. HDTV has 1280 by 720 or 1920 by 1080 digital resolution, which is way higher than the 720 by 480 of DVD. That's why it looks better, even though I notice compression artifacts when there is a lot of movement.  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 03-22-2005 06:08 PM                        DVD = compression artifacts by nature. HDTV ≠ compression artifacts by nature. Only broadcast HDTV because the people who created the current broadcast method are incompetant, as is the equipment. Hook up HDTV with component from your Xbox or PC and you will not see any artifacts. For some reason Jack Valenti doesn't like the idea of HDTV through component. I bet he fucks himself in his own ass on the weekends. Also, DVDs can run at a true 24 frames per second, and so can HDTV. I am not sure if 480p is capable of running at true 24 though.  |  IP: Logged Larry Myers Master Film Handler Posts: 371 From: Herndon, VA, USA Registered: Jan 2001 posted 03-23-2005 12:12 PM                 I have another question. I can change from 480i to 480 p with a switch on my Sony DVD player. When I go back and forth with the switch I notice the 480p image has way more shadow detail then the 480i. Also, the color balance changes. I see it in the faces of people. Color goes from somewhat yellow faces with 480i to more reddish faces with 480p. Could the reason for this be that there are two different burns on the disc. One for 480i and the other for 480p. Larry  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-23-2005 12:19 PM                     It is more likely that it is due to you getting twice as much information on the 480p setting. If you really want to see what is happing...try getting your hands on a DVD pressing with Color bars like the Digital Video Essentials disc (available at Amazon.com). With that you can set color level. You generally can not set Hue with component and higher grade of outputs (since the color space is set) but you can verify that all is as it should be.  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 03-23-2005 05:21 PM                        There is just one "burn" on the disc. The DVD player decides if it will be output at 480i or p depending on how the DVD player itself is set up. It will only output 480i over composite and S-video, though.  |  IP: Logged Bobby Henderson "Ask me about Trajan." Posts: 10973 From: Lawton, OK, USA Registered: Apr 2001 posted 03-23-2005 05:56 PM                     Does anyone here have any experience and opinions to share about the "H264" MPEG-4 codec? I'm pretty sure that one is going to be used in both Blu-Ray BD-Video discs and HD-DVD. Apple is also using it in Quicktime 7. The H264 codec is supposed to be leaps and bounds better than MPEG-2, but that's according to the sales pitch. I'm sure the mileage varies in reality.  |  IP: Logged Evans A Criswell Phenomenal Film Handler Posts: 1579 From: Huntsville, AL, USA Registered: Mar 2000 posted 03-24-2005 10:26 AM                        Larry, another reason you may see differences in 480i and 480p is some sets may use a totally different processing method for 480p. I have a 17-inch Sony HD set in my bedroom and when I used colorbars, I could tell a big difference in color bandwidth between 480i and 480p, just by switching the DVD player. This could be either due to the DVD player having separate signal construction paths for the two, one of which has more color bandwidth, or the set itself samples the color at a higher rate if the signal is progressive. On that little Sony HDTV, transitions between color bars are "perfect" with 480p input. With 480i, using the same DVD player and the same component cables (just switching the player to interlaced), the transitions are no longer "perfect", making it clear that using the 480i causes a loss in color bandwidth (although not in luminance bandwidth).  |  IP: Logged David Stambaugh Film God Posts: 4021 From: Eugene, Oregon Registered: Jan 2002 posted 03-24-2005 11:02 AM                        The 480i signal from a DVD player can be mucked with quite a bit by a TV equipped with something like Sony's Digital Reality Creation. DRC will line-double the picture and otherwise "enhance" the signal. Whether the DRC'd signal looks "better" is sometimes debatable (though it often does look better). And DRC is not defeatable on some sets, so the 480i image being displayed may not be "pure". Transitions on color bars can be affected by the degree of Scan Velocity Modulation being applied (many newer sets allow SVM to be defeated by the user). There's just a lot of things potentially tampering with the signal. Some of these things help, some of them don't. I had an older Sony bigscreen with their first-generation of DRC and it mostly made analog sources like cable TV look worse to me. I have a newer Sony bigscreen now, with a newer implementation of DRC, and it seems to do *much* better with mediocre-quality cable TV. Sometimes, to my eye anyway, good old 480i on a non-DRC set (like my 27" Sony Wega) looks pretty darned good, even with the scan lines.  |  IP: Logged

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