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Notes are 1 indexed, not 0 indexed

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Versions of xmrs below 0.4.1 (unreleased, 0.4.2 is on crates.io but
0.4.1 is in the repo) have a bug where they swap linear and amiga
frequencies. This caused all old versions of agb (which were using
version 0.3) to use the amiga frequency table rather than the linear
one. Technically it sounds slightly wrong but it is kinda hard to tell.

Since agb 0.20.0, we are now using xmrs 0.5, which correctly reports the
frequency type for the XM file. That pointed out an error in the
note_to_speed method for linear frequencies (since those are now being
used). It turns out that the formula for calculating the frequency
expects a 0 based index for the note, but we were passing a 1 based
index for the note. Moving this down a note fixes the issue where things
were being played at the wrong frequency.
This commit is contained in:
Gwilym Inzani 2024-05-15 21:35:03 +01:00
parent 737b547343
commit 2ab3fa79e1
1 changed files with 1 additions and 1 deletions
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tracker/agb-xm-core/src/lib.rs
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@ -482,7 +482,7 @@ fn note_to_speed(
}
fn note_to_frequency_linear(note: Note, fine_tune: f64, relative_note: i8) -> f64 {
let real_note = (note as usize as f64) + (relative_note as f64);
let real_note = (note as usize as f64) + (relative_note as f64) - 1.0; // notes are 1 indexed but below is 0 indexed
let period = 10.0 * 12.0 * 16.0 * 4.0 - real_note * 16.0 * 4.0 - fine_tune / 2.0;
8363.0 * 2.0f64.powf((6.0 * 12.0 * 16.0 * 4.0 - period) / (12.0 * 16.0 * 4.0))
}