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Karaoke player with xor-mode disk anti-glitch logic

Karaoke player that minimizes corrupted on-screen text
 
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On a karaoke CD+G disk, there are four ways of updating the screen:

-1- Scroll the entire screen up, down, left, or right.

-2- Clear the entire screen, filling with a single new background color.

-3- Draw a 6x12 pixel tile with one foreground and one background color.

-4- XOR-plot a 6x12 pixel tile with any single color.

Different CD+G disk vendors use different combinations of these. Unfortunately, some vendors use #4 almost exclusively (Chartbuster and Sweet Georgia Brown among them). Consequently, if there is a glitch during playback which corrupts part of the screen, that portion of the screen will remain corrupted for the remainder of the song.

What I would propose would be for the player to keep track of the last few drawing operations on each 6x12-pixel tile; if they are (xor in one color) (xor the same design in a second color) and (xor in the same design with the xor of the previous two colors), then process the third operation as a request to clear the tile rather than just xor'ing with the same old data.

If a CD+G player incorporated such logic, it would make scratched or damaged disks much less bothersome. As it is, a disk with 0.01% read errors can produce text which is very hard to read; the improved logic descrived above would mitigate that problem substantially.

supercat, Feb 27 2003

Vestigial pelvic structures in snakes. http://taggart.glg....isb200/predarwn.htm
The illustration is about a quarter of the way down the page. [8th of 7, Oct 04 2004, last modified Oct 05 2004]

[link]






       So you want software that will guess when the XOR operation is intended to clear already-drawn graphics and when it's intended to display new graphics? Putting aside the question of how idiotic it is for the disc compilers to implement their graphics in this way, it seems possible.   

       Similar issues exist with video encoding methods which subtract the current frame from the previous frame and encode the difference (e.g. MPEG 4), but these get around the problem by setting blocks to a known value every so often. I don't know if there are any other algorithms used to correct glitches.
pottedstu, Feb 27 2003
  

       Would it not be simpler to take all the karaoke machines, discs, microphones and singers out into the desert, make a huge pile of them, pour accelerant over the pile, and throw on a lighted match ? This would do much to make the world a better place, and would minimise future complaints about track skipping, corrupted video diplays, and people who think that they sing so much better after eight double Bacardi and Cokes.
8th of 7, Feb 27 2003
  

       [8th]: Its vodka and coke, and it generally takes 11 for the vocal chords and snake hips to loosen. Only then can I 'perform'.
Jinbish, Feb 27 2003
  

       <reaches for earplugs>
8th of 7, Feb 27 2003
  

       Curiously, yes. Snakes are evolved from quadrupedal lizards; some snakes ("legless lizards") have vestigial limbs. Apparently, most snakes have a vestigial pelvic structure in their anatomy. But you have to be an expert to spot it; also, you need to unwrap the outer part of the snake first. The snakes themselves normally object strongly to this process.
8th of 7, Feb 27 2003
  

       Haven't you ever seen a Cobra swaying around for a snake charmer ? They're naturals, believe me.
8th of 7, Feb 27 2003
  

       I think we're uncovering a second string to 8th's bow here. Dissecting snakes just to see whether they have a vestigial pelvis. On good days he sews them back up again, before taunting them with cats in his newest moon rocket.
PeterSilly, Feb 27 2003
  

       Ha! a snake could hula-hoop with another snake who is biting its own tail. What a show!!
Zircon, Feb 27 2003
  

       [BinaryCookies]: //Seems like it would be easier to just contain the text and timing data on the discs and have the actual machine put that onscreen.//   

       Perhaps, but there exists a large library of CD+G karaoke material, and the goal would be to design a player which can work optimally with it.
supercat, Feb 27 2003
  

       [pottedstu]: //Putting aside the question of how idiotic it is for the disc compilers to implement their graphics in this way, it seems possible.//   

       Idiotic, certainly. There is no reason to use an xor-mode put any time a tile will not--after the put--contain more than two different colors. Nonetheless, there exist a substantial quantity of disks that use xor for everything. I have no idea why.   

       As for the feasibility of distinguishing draw operations from erasures, I would expect that could be done fairly effectively using the exact procedure I described. Would require a little bit of extra logic, but not a whole lot. Nothing a decent micro couldn't handle.
supercat, Feb 27 2003
  
      
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