Author Topic: OPL limitations under MPTM?  (Read 748 times)

Offline jmkz

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OPL limitations under MPTM?
« on: November 14, 2018, 03:00:11 »
Which limitations have the use of OPL under MPTM?

I'm porting a song to use both samples and OPL, but hard to get close to original sound.
I've noticed issues with:
  • Voices hanging in background
  • Played notes muted (like max. voices reached)
  • No availability to apply effects to mapped instruments or through channels

Offline Saga Musix

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Re: OPL limitations under MPTM?
« Reply #1 on: November 14, 2018, 12:02:07 »
OPL voices can use NNA just like sample voices, so maybe one of your OPL instruments just keeps playing forever which would explain hanging notes and other instruments not being able to allocate any more of the 18 possible voices.
But without a file to look at, all I can do is guess.
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Offline jmkz

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Re: OPL limitations under MPTM?
« Reply #2 on: November 16, 2018, 19:22:43 »
I've managed to reach more consistent sound into the edit, listen to attached file.

Offline Saga Musix

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Re: OPL limitations under MPTM?
« Reply #3 on: November 16, 2018, 22:23:08 »
I cannot give you a detailed analysis right now, but from a quick look what I said in my previous post still holds: With all those NNAs, you will exceed the 18 channel limit of the OPL3 chip. You have 16 pattern channels playing OPL voices, and in particular the last 6 of them are written in a way that two notes are intended to be played at the same time - resulting in at least 22 voices, so at least 4 more than the OPL3 chip can handle.

In general, any limitations appliying to a real OPL3 chip also apply to OpenMPT.
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