Glad to see this finally come! We've been waiting for this. However there are some notes on echoing I'd like to make. After all it's something I written a topic about (which you linked)
Echo Buffer
Originally posted by Wakana- From $80 to $FF you have surround volume
$FF to $80 is not necessarily surround sound. What it does is invert the waveform. If EVOL L= -n R= -n then it will sound identical to MVOL L= +n R= +n, granted no feedback. Because it's not the same phase (180o phase shift) you MAY get surround/panning effects but you also risk having destructive interference.
MVOL $40 $40 EVOL $dC $dC
Originally posted by Wakana$FF being the lowest, $7F being the highest.
$FF is -1, $7F is 127. $80 is -128 making it the lowest. If we're talking volume $FF should be the same as $01. $7F + $01 = $80, and it should continuously get "smaller." Could be wrong and the SPC700 does something different
What generates surround are inverse Volumes, EVOL L= -n R= +n, this would (for example) generate a 45o phase shift. In short the waveform has to be phased a certain way to be matrixed for surround output. This is generally done by using inverse volumes and/or mixing negative and positive FIR coefficients.
MVOL $40 $40 EVOL $dC $24
Feedback Volume
Originally posted by Wakana$7F to $FF you get surround reverb
Basically the same as the above. Negative feedback should phase the waveform 180o. If feedback and echo volumes are negative you should be in-phase with MVOL. 180o + 180o = 360o = 0o
Originally posted by Wakana$0F is max delay (I think?)
Yup! 240ms for 30kb ARAM. Maybe echo buffer writes can change this.
FIR Filter
Originally posted by WakanaThe difference is very thin. To compare them, take a listen to these two spcs: NO FIR WITH FIR
I think the way AMK readme has it is a bit misleading. NO FIR is a "lowpass filter" whereas FIR ON is unaltered sound. Not your fault it's like this but technically it should be the other way around? xD
The filters are explicitly defined in a table so really it doesn't even turn anything off.
Stereo Samples
Originally posted by Wakana- This can be tricky in your .txt, since, in order to play a sample, you need 2 channels and not one.
- This takes double the space.
I believe these reasons alone deter many people from using stereo samples. Effective use of surround sound (and echo) can close the gap between mono/stereo. The main advantage of stereo samples is to realistically capture the acoustics of the given room. A "dry" sound loses very little information mono. Hopefully this example gets the point across.
Stereo,
Mono. The latter uses the echo buffer to help alleviate the deficiency. Unless we had the PSX's 512kb SPU memory then it'd be difficult to properly showcase the power of stereo samples.
Thanks for the guide as it was very much needed here!