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PostPosted: Sun Dec 10, 2017 11:35 am 
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A couple years ago when I wrote a GBA game, I did exactly what tepples described above. Used the two channels directly, one for music and one for sfx. I didn't want to write a mixer, the free-for-commercial-use ones didn't compile or straight crashed at runtime, and the ones that worked required payment.


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PostPosted: Sun Dec 10, 2017 11:43 am 
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Bregalad wrote:
in all cases the screen would drag more power than the CPU

That might be the case on backlit models like the GBA SP. But you'd be surprised.

The original Game Boy Advance had a non-backlit reflective LCD. Its battery light was normally green and turned red when it was low. At certain levels of remaining charge, the light would turn red and green to the beat of the music: mixing more channels (or perhaps driving the audio circuit with more sound) would draw more power. In any case, back when I was homebrewing on the GBA, I could switch the vblank wait between spin-waiting and using the halt SWI and cause the light to change between red and green.


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PostPosted: Mon Dec 11, 2017 1:40 am 
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The saddest part about the GBA is that even though you have the flexibility to push resources for better audio, in the end regardless it's going to be bottlenecked by the piss poor final output mixing.

I wish there was an emulator that could rectify that somehow. It's unbelievable how much better the Megaman Zero DS Collection sounds than the GBA originals. They didn't even remaster the assets or anything, the cleaner output of the DS just brings out the true quality. Wish all GBA games could get that treatment.


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PostPosted: Mon Dec 11, 2017 2:15 am 
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Yeah, I remember reading documentation on how properly using the halts affected battery life. It was substantial.


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PostPosted: Mon Dec 11, 2017 7:07 am 
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If I had to guess it's because the SNES samples probably are compressed to hell. SNES games ranged from 4kbit to I think 32kbit in size (512kbyte to 4mbyte) which encompassed the game code, graphics and any digital audio samples. With finite space they probably had no choice but to compress.
With CD-ROM however, even a graphically intense Genesis game could have hundreds of megabytes of space left over that you could use on music and audio samples. Again this is my best guess but I don't think I'm too far off.

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PostPosted: Mon Dec 11, 2017 7:55 am 
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Sega CD accessory could have only a small amount of data loaded at once: about 6 Mbit. Anything more than that

LOADING

usually required gameplay to freeze for a couple seconds. The FDS had the same problem.


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PostPosted: Mon Dec 11, 2017 8:31 am 
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Do any GBA game use DSP effects like reverb chorus phasing and flanging? Because it's software based, it should make sense to do it.

I wish I had fine control over the SPC700's echo delay, because there are so many DSP effects that involve delay manipulation.
I can do some fine control with the FIR filter, but with only a range of 8 samples.


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PostPosted: Tue Dec 12, 2017 12:21 pm 
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This is my personal opinion, but I think a lot of Genesis games rely too much on overly gritty bass. Just too much high frequency content for bass.


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PostPosted: Tue Dec 12, 2017 4:01 pm 
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Over half the games should have their instruments TL values increased a little (less modulation, less twang and noise sounds etc.), much less abrasive experience... SNES equivalent I suppose is just poor samples, over half the soundtracks had really tiny, terribly looped samples with poor attack parts so that each new note causes a noticable "hiccup".

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PostPosted: Tue Dec 12, 2017 4:23 pm 
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TmEE wrote:
over half the soundtracks had really tiny, terribly looped samples with poor attack parts so that each new note causes a noticable "hiccup".


I think the "hiccups" you're talking about is more of a side effect from the DC resets, which is unavoidable regardless of attack values. The best you can do is mitgate it using the reverb.

I actually have a problem with a recurring bass sample (or several ones that are similar) used in SNES music that sounds too bright. Like, it's meant to be a standard soft guitar bass, but there's a problem with the loop that adds this extra clicky oscillation to it that sounds like it's really not meant to be there.


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PostPosted: Tue Dec 12, 2017 4:59 pm 
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Is it the bass guitar in SMW's boss fights where the loop is slightly out of tune?

With the YM2612, how wide can the frequency sweeps go? When I look at the waveform monitor on TFM tracker, if I put the modulation all the way up, I can see the wave reversing.


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PostPosted: Tue Dec 12, 2017 8:25 pm 
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Highest freq is 53203424Hz / 7 / 144 / 2 ~26390.587Hz on PAL and 53693175Hz / 7 / 144 / 2 ~26633.519Hz on NTSC machines. Going beyond will just alias down, and that's how all the noise type sounds work, overflow into semi-random part in the freq range every sample.
The waveform view in the tracker is subject to its own artifacts that are determined by the refresh rate and what part of the waveform gets shown. It only shows some amount of the output every once in a while. It is like how car wheels appear to rotate backwards in TV and movies at certain speeds.

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PostPosted: Tue Dec 12, 2017 9:19 pm 
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I drew a picture to explain what I mean. FM synth, there should be just a top and bottom of the wave, but sometimes you get these minor peaks and troughs where it appears the wave is going backwards.

Attachment:
FM wave.png
FM wave.png [ 1.99 KiB | Viewed 931 times ]


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PostPosted: Tue Dec 12, 2017 9:22 pm 
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If the amplitude of the modulator is large enough, FM can cause the resulting modulated carrier to visually appear to go "backwards" and not transition all the way from positive to negative extreme.


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PostPosted: Sat Dec 16, 2017 3:44 am 
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Can someone care to explain how the audio in the SNES Lost Vikings port works? Apparently it bypasses the SPC's memory bank entirely. Isn't that very taxing on resources?


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