| LaserDisc Database https://forum.lddb.com/ |
|
| Technical Information & Specifications https://forum.lddb.com/viewtopic.php?f=14&t=117 |
Page 2 of 2 |
| Author: | Guest [ 12 Jul 2012, 10:22 ] |
| Post subject: | Re: Technical Information & Specifications |
publius wrote: The chroma is time-compressed (4:1, from 6 MHz to 24), & then inserted into each line before the luminance signal (which is time-compressed to a smaller degree, 24:20 or 6:5), in a way similar to MAC or in fact MUSE. Thank you for your explanation and the picture. It is a rather complicated scheme used for encoding, but now I think I have understood the principle. Looking at this method I think that the HD picture quality of such a HDVS disc should be better than the quality of a MUSE Hi-Vision disc, on the other hand on a CLV HDVS you have only 15 minutes in comparison with the 60 minutes of a CLV MUSE HiVision disc. Have you ever heard of the TV lines value describing the horizontal resolution quality of the HDVS video signal ? |
|
| Author: | publius [ 12 Jul 2012, 17:47 ] |
| Post subject: | Re: Technical Information & Specifications |
The nominal bandwidth after decoding is the same for MUSE as for this system, ie, 20 MHz, which as I have calculated it is approximately 640 TVL per picture height. For MUSE, however, this applies only to "static resolution", because the encoding reduces the resolution of moving objects, whereas the HDVS system preserves the same resolution (within the limits of the camera) for all subjects. Also, MUSE encoding reduces by half the diagonal resolution, which in orthogonal scanning is normally root-two (1.414) times the horizontal or vertical resolution, while the HDVS system does not. I can say, in terms of picture quality, that I have a MUSE disc, a fairly early one, which includes title cards with approximately 15 lines of 50 characters each of Japanese text (& a wide border around), which is quite legible. So, in those terms, there is little more to wish for. |
|
| Author: | Guest [ 17 Jul 2012, 00:28 ] |
| Post subject: | Re: Technical Information & Specifications |
publius wrote: The nominal bandwidth after decoding is the same for MUSE as for this system, ie, 20 MHz, which as I have calculated it is approximately 640 TVL per picture height. ... I can say, in terms of picture quality, that I have a MUSE disc, a fairly early one, which includes title cards with approximately 15 lines of 50 characters each of Japanese text (& a wide border around), which is quite legible. I wonder how you calculated the TVL from the 20 MHz? Calculating 20000000 Hz divided by 30 and divided again by 1125 results in about 593 Hz/scan line. Only 52/64 of a scan line is used for the picture, i.e. 482 Hz per picture area of one scan line. And because TVL is measured "per picture height", therefore only 9/16 of the horizontal picture width is considered, resulting in 271 Hz covering the TVL-relevant width of the screen. Thinking of 2 TV lines per Hz would result in 542 TVL ... so how did you find the result 640 TVL? Does one Hz actually correspond to 2.36 TVL ?? Or did I miss something? Also I wonder how these 15 lines of 50 "Japanese characters" look like? Japanese uses the very simple looking Katakana characters (カタカナ), the less simple looking Hiragana characters (ひらがな), and the sometimes very complicated looking Kanji characters (漢字) imported from China, and all three character types are usually mixed together in a single sentence (most Japanese names however are written by Kanji only). If 50 Japanese characters in a single line are still "quite legible" also the most complicated character within has to be clearly recognizable - requiring a rather high horizontal resolution of the screen. |
|
| Author: | publius [ 17 Jul 2012, 02:12 ] |
| Post subject: | Re: Technical Information & Specifications |
The master Y sampling frequency of MUSE is 44.55 MHz, or 0.6 times the master sampling frequency of the studio standard. So, the number of elements per picture height is (1920)*(9/16)*(0.6) or 648. Of course, that assumes ideal filters & various other unrealistic things, allowing all 22.275 MHz of theoretically realizable output bandwidth to contain meaningful information, but it's a limit. Do note that the extreme left & right edges are cut off, equivalent to 25 samples on each side at the 74.25 MHz frequency, so that the number of elements per line is only 1122, not 1152. When I say "Japanese characters" I mean a mixture. I'm accustomed to Japanese NTSC LDs, which often have kanji (especially in the credits) at about the limit for legibility, meaning that not all the elements of all the characters are clearly resolved, but there is enough information there to allow you to recognize & read them. The opening & closing title cards on Hills of the Seasons were at least that clear, with characters much smaller & more closely packed. I don't yet have a way to do a high-definition frame capture, or I'd just show you ; I could capture a frame from the NTSC downconversion output of one of my decoders, & compare it to a frame from an NTSC disc with lots of Japanese text, but I don't know how useful that would be. |
|
| Author: | disclord [ 17 Jul 2012, 03:03 ] |
| Post subject: | Re: Technical Information & Specifications |
As Publius knows, but not many others seem to, NHK routinely gave MUSE-E Hi-Vision an "approximate" horizontal resolution of 29 lines per MHz. The ATSC and Grand Alliance used the same figure for 1080i/P. And if memory serves, 21 lines per MHz for 720P. |
|
| Author: | blam1 [ 20 Sep 2017, 04:15 ] |
| Post subject: | Re: Technical Information & Specifications |
In looking at a my copy of "Basic Instinct", it appears Pioneer returned to true CLV for MUSE Hi-Vision discs. Does anyone have any confirmation of which encoding was used? |
|
| Author: | efishell [ 24 Feb 2024, 20:24 ] |
| Post subject: | Re: Technical Information & Specifications |
publius wrote: Of course, you may have to allow for "lead-in" & "lead-out" tracks which do not contain valid picture information, but allow the player to get synced up & locked in. The chroma is time-compressed (4:1, from 6 MHz to 24), & then inserted into each line before the luminance signal (which is time-compressed to a smaller degree, 24:20 or 6:5), in a way similar to MAC or in fact MUSE. I suppose I was not clear enough before in my description of the encoding ; unfortunately, the forum settings will not allow me to attach the paper to this post ("The extension pdf is not allowed"). So that you can see for yourself how it works, I have captured an image which shows the most important details. I have to say that I am not sure what they did about the fact that there is an odd number of lines per frame. Do you have a photo of Sanyo Baseband discs? |
|
| Page 2 of 2 | All times are UTC [ DST ] |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|