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Thread: Mega Man X & Sega Genesis

  1. #361
    Hero of Algol Kamahl's Avatar
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    AMPS should be a big new contender for MD sound. It has different tradeoffs than XGM.

    1. XGM has 4 PCM channels, AMPS has 2 PCM channels.
    2. The quality of the XGM PCM channels is fixed, AMPS's is variable (both are ~14KHz but you can use pitch shifting to play samples at any KHz in AMPS).
    3. AMPS can change the pitch and volume of the PCM channels, i.e., they can be used for all sorts of instruments, not just drums.
    4. XGM runs all on the Z80, while AMPS runs on the 68k, with MarkeyJester's DualPCM FlexEd handling the PCM channels on the Z80.
    5. XGM is designed to have easy conversions from VGM (as exported by Deflemask) while AMPS is designed to have easy conversions from SMPS (the Sonic sound driver).

    Very different beasts, whichever one is best will depend on the game. For music AMPS will be the winner though since it can sound like this:



    Last edited by Kamahl; 04-25-2020 at 07:28 AM.

  2. #362
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    AMPS running off the 68k means tying tempo to 60hz (or 120hz if they use hsync interrupt). I thought some of the z80 drivers were like the PCE and SNES, where tempo is dependent of 'tick', or is XGM not like that?

  3. #363
    Hero of Algol Kamahl's Avatar
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    AMPS's documentation says the following: "In PAL regions, Mega Drives run at 50hz as opposed to 60hz. The driver combats this by running twice every 6th frame. This causes timing issues with things that run for a specific amount of time."

    Here's an overview of the homebrew sound drivers for the MD:

    Compatibility:
    - XGM: VGM (standard for sega music rips)
    - AMPS: SMPS (sonic sound driver)
    - Echo: XM & DMF (tracker formats)
    - TmSE: None (custom tracker)

    PCM:
    - XGM: 4 channels at 14 KHz, fixed pitch.
    - AMPS: 2 channels at 14 KHz with pitch shifting and volume control.
    - Echo: 1 channel, configurable from 4 to 26 KHz.
    - TmSE: 2 channels at 22 KHz, fixed pitch (might have volume control).

    Type:
    - XGM: Z80 + 68k "beat"
    - AMPS: 68k
    - Echo: Z80
    - TmSE: Z80

    Sound effects:
    - XGM: Only PCM sfx supported, all 4 channels.
    - AMPS: FM3, FM4, FM5, PSG1, PSG2, PSG3, and DAC1.
    - Echo: FM, PSG or PCM, but only 1 at a time.
    - TmSE: FM or PCM, up to two?

    License:
    - XGM: MIT
    - AMPS: Apache 2.0 (SMPS compatibility makes it a bit legally grey)
    - Echo: Zlib
    - TmSE: Closed-source, not publicly available.

    It's funny how they're pretty much all better than the ones released back in the day
    Last edited by Kamahl; 04-25-2020 at 09:07 AM.

  4. #364
    Raging in the Streets Sik's Avatar
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    OK, gonna fix some misunderstandings there:

    Quote Originally Posted by Kamahl View Post
    AMPS's documentation says the following: "In PAL regions, Mega Drives run at 50hz as opposed to 60hz. The driver combats this by running twice every 6th frame. This causes timing issues with things that run for a specific amount of time."

    XGM runs 100% on the Z80 and is unaffected by PAL/NTSC differences as far as music playback goes.
    XGM also does the same thing from what I remember (it relies on the 68000 to do the "beat", even if the rest of the driver runs off the Z80), so it's not better than AMPS in this sense. I think you can configure the rate to other values though (acting as a form of tempo).

    I forgot how TMSE timed itself (vblank or YM2612) so no comment but it tries to run at 50Hz, while Echo relies exclusively on the YM2612 for that and runs at 60Hz (unless it's Tanglewood, which reconfigures timer B to run at 50Hz).

    AMPS is probably the only one of these that runs mainly off the 68000 tho (XGM runs off the Z80 aside from the beat, Echo and TMSE are 100% Z80).

    Quote Originally Posted by Kamahl View Post
    Compatibility:
    - XGM: VGM (standard for sega music rips)
    - AMPS: SMPS (sonic sound driver)
    - Echo: XM (standard for old-school trackers)
    - TmSE: None (custom tracker)
    There's a dmf2esf that lets you use Deflemask with Echo now. There's also mml2esf (for MML) and midi2esf (for MIDI) though I haven't touched the latter in ages and I don't trust it with some edge cases (and can be kinda unintuitive at times).

    Quote Originally Posted by Kamahl View Post
    PCM:
    - XGM: 4 channels at 14 KHz, fixed pitch.
    - AMPS: 2 channels at 14 KHz with pitch shifting and volume control.
    - Echo: 1 channel, configurable from 4 to 26 KHz (slightly different between PAL and NTSC).
    - TmSE: 2 channels at 22 KHz, fixed pitch (might have volume control).
    The "slightly different between PAL and NTSC" part applies to everything, not just Echo (it's because of the difference in master clocks, so something taking the same amount of clock cycles will still take different time because of that). It's so minimal that I'm not sure it's even worth mentioning, I only document it because I know some people are pedantic as fuck lol (e.g. Echo's default rate is documented as "10650Hz", but it's actually either ~10652Hz or ~10649Hz depending on whether it's NTSC or PAL).

    Quote Originally Posted by Kamahl View Post
    Sound effects:
    - XGM: Only PCM sfx supported.
    - AMPS: no restrictions
    - Echo: no restrictions
    - TmSE: no restrictions
    "No restrictions" is kinda misleading :​P

    • XGM only allows PCM sound effects, but all PCM channels can be used (in practice you don't want to stomp on the channels used by music, but you get the idea).
    • AMPS has more or less the same restrictions as SMPS I think, but I need to check carefully.
    • Echo allows any use of FM, PSG or PCM for sound effects, but it's limited to one sound effect at a time (ouch).
    • TMSE doesn't allow PSG in sound effects if I recall correctly. I also forgot how many sound effects it allowed at a time (two?).

    Quote Originally Posted by Kamahl View Post
    License:
    - XGM: MIT
    - AMPS: Apache 2.0 (SMPS compatibility makes it a bit legally grey)
    - Echo: Zlib
    - TmSE: Closed-source, not publicly available.
    Isn't AMPS written from scratch? As far as I'm aware it's compatible with SMPS as a format, but not using any actual SMPS code. That should be legally safe, especially since any patents Sega may have held on SMPS are long dead by now simply due to how old they'd have to be (there's no way in hell that any such patents were filled from 2000 onwards).

    Quote Originally Posted by Kamahl View Post
    It's funny how they're pretty much all better than the ones released back in the day
    Echo is arguably worse than most of those :​P Also to be fair, Z80 SMPS was the big sore. Freaking thing will pause PCM playback like about 1/3 of the frame or so every frame to process FM and PSG. Uneven doesn't even begin to describe it. What the fuck, Sega? Most other sound drivers that do PCM do better than this.

    Incidentally, GEMS can be actually pretty damn good under the right hands. But apparently the tools sucked (they surely looked like a pain to set up at least) and that pretty much limited what composers could do. From what I recall this is what happened with XBAND, the reason why the music is much nicer on SNES than Mega Drive is that in the latter case the composer spent too much time fighting with getting GEMS to work and when they finally did it there was little time left to actually compose, so it was kinda rushed. Whoops.

  5. #365
    Hero of Algol Kamahl's Avatar
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    Thank you for the corrections, I'll apply them to the post for clarity. The AMPS warning comes from the documentation:

    Although AMPS is open source and free to use for commercial purposes, because it is technically based on SMPS, which is property of SEGA, it may not be a good idea to use for commercial purposes.

  6. #366
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    Quote Originally Posted by Kamahl View Post

    It's funny how they're pretty much all better than the ones released back in the day
    Also very believable though (from working and RE sound engines from other systems around that era).


    Interesting. So I take there no Genesis music engines that are not tied to vsync for tick timing (or not multiple if it)? I'd imagine it would be extremely difficult to do on the z80 if there's PCM playback too.

  7. #367
    Hero of Algol Kamahl's Avatar
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    Quote Originally Posted by turboxray View Post
    Interesting. So I take there no Genesis music engines that are not tied to vsync for tick timing (or not multiple if it)? I'd imagine it would be extremely difficult to do on the z80 if there's PCM playback too.
    From what I understand, while they are 60 or 50Hz, they don't necessarily get the timing from vsync, the pure Z80 drivers do something else (e.g. Echo uses the YM2612 timers).
    So they are PAL/NTSC agnostic, but not 50/60Hz agnostic.

    Not being a musician, 60Hz seems pretty reasonable to me. I know some Amiga games add an extra interrupt for the sound driver, making it 100Hz, but that's because of the low channel count and the need to constantly switch instruments to sound a bit fuller.

    Come to think of it, Sik maybe you know, but what does the Titan driver do? It's based on Echo (afaik) and probably plays at 1000Hz which is the bare minimum required by strobe .
    Would be nice if they released it for general use, even though it is very much targeted at just music playback.

  8. #368
    Raging in the Streets Sik's Avatar
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    Echo doesn't use vblank at all, it does its timing based off YM2612's timer B (while PCM is based off timer A). The only reason for sticking to 60Hz is because that's what we're accustomed to (it's easier to think in terms of "frames" after all, even if Echo's ticks aren't strictly tied to frames), and you can change that value by changing the rate of timer B (though that'll affect everything, not just music tempo).

    EDIT: postninja'd lol
    Quote Originally Posted by Kamahl View Post
    Come to think of it, Sik maybe you know, but what does the Titan driver do? It's based on Echo (afaik) and probably plays at 1000Hz which is the bare minimum required by strobe .
    Overdrive 1 is… forgot if timer B was meddled with or not, but I guess it's 50Hz. It wasn't modified that much, and several of the changes got backported to mainstream Echo in 1.3 (you aren't really missing anything by this point, the other changes were mostly removing features that weren't needed like sound effect support).

    Overdrive 2 uses its own whole custom thing instead of something based on Echo.

  9. #369
    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert retronostalgia's Avatar
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    Guys this is great info, I really appreciate you writing up the details.

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    Quote Originally Posted by Sik View Post
    Echo doesn't use vblank at all, it does its timing based off YM2612's timer B (while PCM is based off timer A). The only reason for sticking to 60Hz is because that's what we're accustomed to (it's easier to think in terms of "frames" after all, even if Echo's ticks aren't strictly tied to frames), and you can change that value by changing the rate of timer B (though that'll affect everything, not just music tempo).

    EDIT: postninja'd lolOverdrive 1 is… forgot if timer B was meddled with or not, but I guess it's 50Hz. It wasn't modified that much, and several of the changes got backported to mainstream Echo in 1.3 (you aren't really missing anything by this point, the other changes were mostly removing features that weren't needed like sound effect support).

    Overdrive 2 uses its own whole custom thing instead of something based on Echo.
    Ohh.. so Echo can run at say 72hz for the tick and doesn't have issues running async with vblank (for issues with vdma stalling PCM.. i.e. you detect when vblank happens and jump into ram to avoid bus conflict, which still maintaining a tick system drifting asynchronous to vblank).

  11. #371
    Master of Shinobi Pyron's Avatar
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    Im on favor of XGM because runs on z80 and free the 68k to handle the rest of the game..
    also the extra PCM channels help you bring the all the arcade glory of YM2151 + OKI,
    FM with pcm sampels used with wisdom is far more impressive for me than these massive boring music sample based demos.

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    Quote Originally Posted by Sik View Post
    Incidentally, GEMS can be actually pretty damn good under the right hands. But apparently the tools sucked (they surely looked like a pain to set up at least) and that pretty much limited what composers could do. F
    Wasn't GEMS actually pretty usable for MIDI composers, but the bulk of the work was creating a good set of patches ? Which made nearly everyone use the default patches which were made as examples and not HQ, ready for games.
    Tommy Tallarico used GEMS and it sounds great.

  13. #373
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    Tommy Tallarico
    2 years ago
    Yo! Thanks so much for the trip down memory lane! G.E.M.S. was definitely the best sound driver/editor that was made available to the general public during the first half of the 90's. I absolutely loved it... and this video really captured all of incredible stuff it could to for the time. Before G.E.M.S. (as the video rightly mentions)... we as composers/sound designers had almost nothing. So glad this video was made. It will hopefully be a part of video game history for many years to come. I wish more people documented stuff like this for future generations to learn about the challenges we faced in the early years. THANKS!! Amazing job!!

  14. #374
    Hero of Algol Kamahl's Avatar
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    Quote Originally Posted by Pyron View Post
    Im on favor of XGM because runs on z80 and free the 68k to handle the rest of the game..
    also the extra PCM channels help you bring the all the arcade glory of YM2151 + OKI,
    FM with pcm sampels used with wisdom is far more impressive for me than these massive boring music sample based demos.
    While those arcade covers sound absolutely amazing, they are using ridiculous amounts of ROM space for all the PCM samples, since they need to store a separate sample per note.
    Hyper Duel is actually using PCM for the bass and is over 4 MB, for one song! You are not pulling that off in a game

    With AMPS you could play all those notes with one stored sample, though you wouldn't be able to fully reproduce the song since you only have 2 PCM rather than 4.
    While XGM can better reproduce those songs, with AMPS you might actually be able to do a cut down version that works in a game.

  15. #375
    Death Bringer ESWAT Veteran Black_Tiger's Avatar
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    I prefer pure chip sound (FM + PSG) or chip sound with minimal samples for games and the kind of style Savaged Regime tends to use isn't my favorate, but it would be a shame if that version (sample effects and voice and all) gets tossed altogether.

    I prefer Mega Drive sound that isn't trying to sound "realistic" or like anything else. That's why I love the sound of so many of the earlier games.

    Same with Neo Geo. We didn't get nearly enough FM heavy soundtracks before sampling took over.
    Quote Originally Posted by year2kill06
    everyone knows nintendo is far way cooler than sega just face it nintendo has more better games and originals

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