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Author Topic: Question about Volume Slide (Axy)  (Read 1262 times)

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DZ-Jay

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Question about Volume Slide (Axy)
« on: February 27, 2024, 20:00:05 »

Hello,

Yes, I am still working on my project.  I had some major set-backs (more than before), and have to come up with a brand now way to encode the data.  That lead to a re-writing of the music player, instrument synthesizer, and the effect handlers.

The good news is that I've been looking at a C port of the FT2 source code to guide my understanding of the effects in the original XM implementation.  This has been very helpful indeed, and I have managed to implement (correctly) Portamento Up/Down, Note Portamento, Arpeggio, Vibrato, and I'm in the process of completing Volume Slide.

I do have one question on the Volume Slide (Axy) effect.  Suppose I have an instrument volume envelope enabled, does the Volume Slide effect respect it, or does it actually adjust the absolute volume of the note?

Let me give you an example.  If someone sets a volume slide to go up, and lets it go up all the way to maximum volume, does the note continue playing at maximum volume even if the envelope is in decay?

If I am reading the source code of FT2 correctly, it seems that the Volume Slide effect ignores any modulation on the volume of the note, and produces an output based on the "real" volume of the note (the one in the pattern data) modified by the slide.

I hope this question makes sense.

     -dZ.
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looper231

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Re: Question about Volume Slide (Axy)
« Reply #1 on: February 28, 2024, 08:34:19 »

The volume slide effect ignores the envelope and slides the sample volume value when triggered
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DZ-Jay

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Re: Question about Volume Slide (Axy)
« Reply #2 on: February 28, 2024, 13:23:11 »

The volume slide effect ignores the envelope and slides the sample volume value when triggered

Hi, looper231,

Thank you for your helpful answer, as always.  That seems to jive with what I see in the source code of the FT2 port.

I have another question on the Volume Slide:  Does the updated volume after the slide remain when the effect is stopped?  I believe it does.

For example, consider the following pattern:
Code: [Select]
00 C-4 -3 0 A30     <- Start slide upwards from volume zero (fade-in)
01 --- -- - A30
02 --- -- - A30
03 --- -- - A30
04 --- -- - A30
05 --- -- - A30
06 --- -- - A30
07 --- -- - A30     <- End slide
08 --- -- - ---
09 --- -- - ---
10 --- -- - ---
11 --- -- - ---
12 --- -- - ---
13 --- -- - ---
14 --- -- - ---
15 --- -- - ---

In row #7, the effect ends.  I imagine that the note continues playing at the last volume the slide left it in.  Is this correct?

Also, at that point, would the envelope kick in again, or is it now lost until the note is re-triggered or replayed?

    -dZ.
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looper231

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Re: Question about Volume Slide (Axy)
« Reply #3 on: February 29, 2024, 06:26:56 »

The volume slide effects persist even after the commands, meaning that you'd have to initialize the note again to get the volume back.
The envelopes are still in effect by the way, so your note might fade out with the envelope faster than it would do with effect commands. You'll most likely never see volslide used on instruments that have the fade out. the command doesn't fully ignore the envelope however, it it still keeps track of it, so you can have a tremolo with envelopes and fade out with volume slide at the same time.
Note that the command has a 00 value, which just continues the value that was specified in the earlier row.
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DZ-Jay

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Re: Question about Volume Slide (Axy)
« Reply #4 on: February 29, 2024, 13:26:33 »

The volume slide effects persist even after the commands, meaning that you'd have to initialize the note again to get the volume back.
The envelopes are still in effect by the way, so your note might fade out with the envelope faster than it would do with effect commands. You'll most likely never see volslide used on instruments that have the fade out. the command doesn't fully ignore the envelope however, it it still keeps track of it, so you can have a tremolo with envelopes and fade out with volume slide at the same time.
Note that the command has a 00 value, which just continues the value that was specified in the earlier row.

Hi, looper231,

This is very helpful indeed.  Thank you so much for the detailed response.  It sort of fits with how I would expect it to work.

I have now implemented it just like you described above.  So, if the envelope fades-out to zero before the slide, it just stays at zero.


The reason that I ask about the envelopes is that for my case, my target CPU is too slow (and the platform too limited) to play digital samples, so the only "instruments" we can use are modulated tones generated by the AY-3-8914 sound processor.  Hence, in my player, all "samples" are just square waves modulated by software-controlled envelopes.   So, it is very likely (actually, I would say practically required) for all "instruments" to have an envelope to shape its sound.

Ultimately, it is more of a "chip-tune" player than a "module player" -- but one that I hope will function close to typical XM players, at least in its effects capabilities.

   -dZ.
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DZ-Jay

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Re: Question about Volume Slide (Axy)
« Reply #5 on: February 29, 2024, 14:15:11 »

I have a related question about the Tremolo (7xy) effect:  The MilkyTracker documentation says that the "volume is not reset when the command is discontinued."

https://milkytracker.org/docs/MilkyTracker.html#fx7xy

However, the ported FT2 source code I am looking at (which aims to have bit-perfect parity with the output of FT2) suggests that only the output volume of the channel is modulated, but the note volume is not altered.  (This is similar to the Vibrato effect, which returns the note to normal after it is discontinued.)

This is in contrast to the Volume Slide effect, which (as we have discussed) does affect both the output volume and the note volume -- resulting in the volume being left in its final state when the effect is discontinued (and envelopes continuing).

I would expect that when I stop the tremolo, the normal volume of the note would return.

Any insights on this one?  Perhaps MilkyTracker docs are inaccurate ...

    -dZ.
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looper231

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Re: Question about Volume Slide (Axy)
« Reply #6 on: March 01, 2024, 17:42:31 »

Any insights on this one?  Perhaps MilkyTracker docs are inaccurate ...

Can't give any, since I haven't used Milkytracker at all... You'd have to check in practice
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DZ-Jay

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Re: Question about Volume Slide (Axy)
« Reply #7 on: March 01, 2024, 21:31:34 »

Any insights on this one?  Perhaps MilkyTracker docs are inaccurate ...

Can't give any, since I haven't used Milkytracker at all... You'd have to check in practice

No worries.  The reason I asked is that MilkyTracker purports to reproduce the module replay experience of DOS FastTracker II and Amiga ProtTracker 2/3.  I figured those two were the model for modern trackers.

Anyway, I hope you do not mind if I ask you a follow up question.  In your experience with other trackers, would you say that the Tremolo effect should work like the Vibrato effect, except on volume instead of period (i.e., the note volume is restore at the end of the effect)?

     -dZ.
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looper231

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Re: Question about Volume Slide (Axy)
« Reply #8 on: March 02, 2024, 13:31:06 »

Anyway, I hope you do not mind if I ask you a follow up question.  In your experience with other trackers, would you say that the Tremolo effect should work like the Vibrato effect, except on volume instead of period (i.e., the note volume is restore at the end of the effect)?
     -dZ.
For consistency, I'd prefer tremolo to reset to sample's volume value once it's done
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DZ-Jay

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Re: Question about Volume Slide (Axy)
« Reply #9 on: March 02, 2024, 13:51:07 »

Anyway, I hope you do not mind if I ask you a follow up question.  In your experience with other trackers, would you say that the Tremolo effect should work like the Vibrato effect, except on volume instead of period (i.e., the note volume is restore at the end of the effect)?
     -dZ.
For consistency, I'd prefer tremolo to reset to sample's volume value once it's done

Thank you, I feel the same way.  So it shall be. :)

     -dZ.
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