Martin Smith wrote:
Can I ask which part of the CDG revealed document you think had the typo?
Hi Martin,It was the paragraph near the beginning, which says "The middle 294 x 204 area is within the TV's 'safe area', and that is where the graphics are displayed." Attached is a brief email exchange I shared with Jim Bumgardner, the original author of the document in question, describing the problem.
I've been working on a Java implementation of this for a bit, and that document can be a bit vague. Also, none of the CDGs I have seem to have scrolling instructions, though I only have one vendor's worth. Perhaps we should start a new & improved document with more information about CDG, or just make some of it more plain -- if there's no weird legal issues with that (in FL, USA here, and I think there's legal issues with the red book spec being described in this country). Either way, I enjoy using PyKaraoke, and appreciate all your hard work.
I agree it is a more than a little confusing in parts, especially in regards to the scrolling. I think we have by now worked out precisely what it means.
I really have no idea what the legal issues with producing a clearer document would be. We haven't referenced or even read the official spec, but nowadays it may be illegal even to reverse-engineer a spec, thanks to that marvelous work of legislature, the DMCA.
David
--- Begin Message ---My guess is that 288 x 192 is the size of the interior area, although I'll need to reexamine my old code to confirm. - Jim On 7/11/06, David Rose <[EMAIL PROTECTED]> wrote:Greetings! Let me express my appreciation for your having written that most excellent document, "CD+G Revealed: Playing back Karaoke tracks in Software." Here it is, eleven years later, and it's still the de facto reference available on the internet for understanding CD+G! I was working on some contributions to the PyKaraoke project at http://www.kibosh.org/pykaraoke/ . Specifically, I'm helping port the project to the handheld GP2X device, making perhaps the world's first karaoke machine that fits in your pocket. (Actually, this effort of mine started on a bet--a friend challenged me to bring a solar-powered karaoke machine on our camping weekend. I got an initial port of PyKaraoke working on my GP2X, and brought it and a solar-powered battery charger, thus winning the bet. And then we all enjoyed a round of karaoke at the campfire.) So, my thanks for writing such a clear and readable document, which made PyKaraoke possible (and which, in turn, made it possible for me to win my bet). I have a second reason to write you today, however. There's a minor point that seems a little bit ambiguous in your document. Near the beginning, you state that "16 color graphics are displayed on a raster field which is 300 x 216 pixels in size. The middle 294 x 204 area is within the TV's 'safe area', and that is where the graphics are displayed." But later on, you say "The border area is the area contained with a rectangle defined by (0,0,300,216) minus the interior pixels which are contained within a rectangle defined by (6,12,294,204)." If by (6,12,294,204), you mean the rectangle from point (6,12) to point (294,204), then it describes a visible area of size 288 x 192, not a rectangle of size 294 x 204, contradicting the earlier paragraph. But that rectangle seems reasonable otherwise, and it means that the border area is 6 pixels on the left and on the right, and 12 pixels on the top and on the bottom. On the other hand, if by (6,12,294,204), you mean the rectangle from point (6,12) and extending for 294 x 204 pixels, then this is consistent with the earlier paragraph, except that the rectangle so described is not actually centered within the entire 300 x 216 region--in fact, it's anchored at the lower-right corner, with a border area of 6 pixels on the left only, and 12 pixels on the top only. So we have two possible interpretations: the middle area is either 288 x 192 and centered in the screen, or it is 294 x 204 and anchored to the lower right. Which interpretation is correct? Thanks for your help, David
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