PCM on the Genesis

Discussion in 'General Sega Discussion' started by Rusty, Jan 6, 2009.

  1. Rusty

    Rusty

    pixelated panda pal (previously BMF54123) Oldbie
    47
    4
    8
    Henderson, NV
    existing
    I used to open ROMs in GoldWave all the time, looking for raw samples. They're far more common than you think. (Unless you guys are looking for actual WAV/VOC/etc. file headers and such, in which case I'm slightly more intrigued.)

    Games I know of with raw samples, off the top of my head:

    - Ristar
    - Tempo (32X)
    - Aladdin (probably most games by this team, like Cool Spot, Earthworm Jim, etc.)
    - Crüe Ball
    - Dr. Robotnik's Mean Bean Machine
    - Game Gear Sonic games (at least one of them had a raw SEGA sample)

    I'm curious, though—why do so many games have full-quality samples inside when the hardware is incapable of playing them? Or am I just not understanding exactly how the Genesis handles sample playback?
     
  2. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
    6,719
    0
    0
    being an asshole =P
    The reason the MD didn't have good PCM playback was because it simply wasn't worth it back then. Decompressing samples in real-time would be too slow in that hardware, and uncompressed samples simply take up too much memory. Hence nobody wanted to use them, and things like PSG and FM were made.

    So yup, it's pretty much a memory constraint issue mainly.
     
  3. TmEE

    TmEE

    Master of OPL3-SA2/3 Tech Member
    1,726
    0
    16
    Estonia, Rapla City
    T-04YBSC-A !
    Sample playback on MD is totally software driven, the better your code, the better things sound. You can do up to 60KHz sample playback on MD, if you go over it, then the YM2612 starts to think its a good time to stop functioning until a reset has been issued. Only pity is you cannot play stereo samples... this works beautifully in Fusion :(

    Most games tend to have ineffective or otherwise poor coding done in their sound engines so the playback is a bit jerky. There are plenty of examples of where things are done right... one such is Atomic Runner / Chelnov. Listen that and never tell me MD cannot do decent sample playback. When things go mutichannel... you will be creative thanks to one teeny weeny decision Sega made in the banker that Z80 uses to look into the ROM :)

    All games are full of raw samples... finding something which your average media player can understand is another story though :)
     
  4. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
    6,719
    0
    0
    being an asshole =P
    Or even worse, they can't play PCM and non-PCM at the same time (completely stopping the BGM to play the waveform through the DAC). For no reason, as it still sounds horrible. That annoys me to hell.
     
  5. Overlord

    Overlord

    Now playable in Smash Bros Ultimate Moderator
    18,028
    262
    63
    Berkshire, England
    Learning Cymraeg
    I'd imagine almost every game with speech in uses PCM - of your list, I know Aladdin, Ristar and Mean Bean Machine do, while confirming your "probable" stat for EWJ on the same grounds. Sonic 2 also uses PCM for the Sega sound at the start.

    That's an easy way of finding them, look for games that speak to you! =P
     
  6. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
    6,719
    0
    0
    being an asshole =P
    Also most games have drums as PCM samples. Basically, log the game. If it uses the DAC, it has PCM, because no game generates waveforms on the fly as far as I know =P
     
  7. Nemesis

    Nemesis

    Tech Member
    Derailing a bit, but I never quite got what you meant by that when you mentioned it on SpritesMind. Do you mean that DAC data is always sent to both the left and right channels, regardless of the state of the L/R enable flags for channel 6?
     
  8. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
    6,719
    0
    0
    being an asshole =P
    From what I understood when he told me about it when he had just tried, the sound was screwed up. Basically: a channel gets immediately mute when switched when the DAC is set to only the other one, which is what he was doing. Making it useless. I find it strange that Fusion retains the waveform though - common sense would have told that channels would mute =/

    Then again, I repeat: stereo is only useful if speakers are separate enough in proportion to the distance to the listener. If you use headphones, it works. If you use the speakers that are on each side of the TV that is two meters in front of you, it won't, because speakers are pretty much in the same place, losing the effect.
     
  9. TmEE

    TmEE

    Master of OPL3-SA2/3 Tech Member
    1,726
    0
    16
    Estonia, Rapla City
    T-04YBSC-A !
    You only have one sample "accumulator", and the sample is always being played... now if you write a sample, the output state of a channel is held at the level the sample "says"... now you switch the LR setting, and that same sample will continue playing in the other channel. I had an idea that before writing next sample, I'll turn off the output, but it still did not give any positive effect... playing more than one sample in one channel and then the other, will still not yeld any good effects. You're just panning a single channel... if you'd have 2 DACs, like Fusion seems to emulate (one per LR) things would be sweet.