What about Sega CD?

Discussion in 'General Sega Discussion' started by RamiroR, Sep 13, 2008.

  1. RamiroR

    RamiroR

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    well the first weird thing, it's true that the sega cd escales/rotates the sprite and then it send it to the vdp ram then I'ts displayed like a background?

    why Sonic CD was about to have loop music.. and then.. anything?

    somebody knows for why is usually used the co-68000?

    how can be used a Sine or Cosine function? I mean.. how to program that :P

    I want to talk about these things :P
     
  2. TmEE

    TmEE

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    T-04YBSC-A !
    Do not even think about touching MCD before mastering MD (which you haven't yet).

    One use of SIN/COS, this draws a colorful circle... or should, I don't remember when I last used SIN/COS in QB45... I think these required radians instead of degrees...

    Screen 13
    RingY%=100:RingX%=100:Radius%=50
    For I%=0 to 359
    pset (RingX%+Sin(I%)*Radius%,RingY%+Cos(I%)*Radius%), I% and 255
    next I%
     
  3. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
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    What he said =P

    The VDP is not touched when the Sega CD is used. The Sega CD has an AISC that will rotate/scale/skew (scan-line algorithm) a bitmap into its own RAM, and then you have to blit it into VRAM as you would do with any normal tiles. It's for this very same reason that the Sega CD doesn't improve color, it doesn't touch the VDP.

    Maybe they had trouble with the timing? =P

    Accessing the CD, decompressing FMVs, rendering bitmaps, doing expensive processing (as it's faster than the main 68k). Basically all the job that is Sega CD-only.

    Sine and cosine are normally stored as pre-calculated tables (given an angle, you get a value). Calculating them in real time can be dangerous to your health =P Also, TmEE said they can be used to draw circles, but their most common use in games is to move objects a specified distance at a specified angle.
     
  4. RamiroR

    RamiroR

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    ok ok but I'm just asking! :P

    I was thinking.. it's possible to convert all sonic cd CDA audio to PCM? then try to loop it?.. did somebody do something like this?:O
     
  5. theSTHguy

    theSTHguy

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    The Shadow Odyssey (TSO)
    Sonic CD JPN/PAL Looping Project
     
  6. RamiroR

    RamiroR

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    "Http:/info.sonicretro.org/Sonic CD JPN//PAL Looping Project
    From Sonic Retro
    There is currently no text in this page, you can search for this page title in other pages or edit this page."
     
  7. theSTHguy

    theSTHguy

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    What happened there?! You may want to try that again; works fine for me.
    Wiki -> Music -> Sonic the Hedgehog OSV Project -> Sonic CD JPN/PAL Looping Project
     
  8. muteKi

    muteKi

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  9. RamiroR

    RamiroR

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    now it works.. I don't know why :P.. but.. I mean.. there's no code yet?(for the looping project)
     
  10. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
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    It would, but I'm not sure if there's enough RAM to fit it. You could load the data in run-time while it's playing, but then you could just use the CDA if you're going to do that.
     
  11. RamiroR

    RamiroR

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    yes.. I'm talking about load the data in run-time. BUT, with the diference that with this.. you can loop.. I think..
     
  12. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
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    No, because once the data is over, you have to seek back to the beginning, and that takes time, hence breaking the loop. So in that case it would be the same as using CDA, there'll be a gap anyways. Fading was made to hide that and make it look like done in purpose.
     
  13. RamiroR

    RamiroR

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    Well an image is better than 1000 words...I don't know how to say it in english so:
    [​IMG]

    EDIT: with Music Beginning I'm refering to the loop point (just if it's the second time or higher)
    sorry about the ugly drawing, I was lazy to make it better :P

    EDIT: OMG OMG, Type error: it was RAM not VRAM!.. that's because I just thinking in VRAM this days :P thanks Sik, (I don't want to waste my last post so I edit here:P)
     
  14. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
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    1) I hope that by "Sega CD VRAM" you mean "Sega CD RAM". The Sega CD doesn't have VRAM.

    2) It doesn't look very clear =/
     
  15. TmEE

    TmEE

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    If a rather big RAM buffer is used, you can have looping music (buffer as big that while the drive is seeking, music is still played from the buffer). The quality will be limited to what the PCM chip in MCD can do though. Quite a few games do it.
     
  16. RamiroR

    RamiroR

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    yes.. doing that and this:

    the sega cd pcm channel frequency is limited a 32hz (if I remember well) , so.. if I speed up a bit.. can be 44hz, the cd quality..I think that Sonic CD was about to do that with these loop sample which was never used.. because when I converted the sample to an wav file.. the music sound a bit slower.. so I think it was to speed it up so can reach the 44hz quality :rolleyes:

    I'm sure that there's something that I said that it's wrong because I don't remember exactly this thing on Sega CD