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[WIP] Add audio time-scale and pitch modification functionality #71
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e928c15
Initial plan
Copilot de322b5
Add audio pitch shifting functionality with interpolation
Copilot 4b129a2
Add documentation for pitch shifting feature
Copilot 385cc49
Fix code review issues - correct playback position tracking and reduc…
Copilot f65f161
Changes before error encountered
Copilot 3f01ba9
sl
charneykaye 75e747a
Fix CI build errors - update SetFireWithPitch API to include ADSR par…
Copilot 503b190
Apply PR review feedback - fix bugs and improve API design
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,122 @@ | ||
| # Audio Pitch Shifting | ||
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| Mix now supports pitch shifting audio without manual resampling, allowing you to change the pitch of audio sources dynamically. | ||
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| ## Usage | ||
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| Use `SetFireWithPitch()` instead of `SetFire()` to enable pitch shifting: | ||
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| ```go | ||
| import ( | ||
| "time" | ||
| "github.com/go-mix/mix" | ||
| ) | ||
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| // Normal playback (with ADSR envelope disabled) | ||
| mix.SetFire("sound.wav", time.Duration(0), 0, 1.0, 0, 0, 0, 1.0, 0) | ||
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| // Pitch shifted up one octave (2.0x pitch), ADSR envelope disabled | ||
| mix.SetFireWithPitch("sound.wav", time.Duration(0), 0, 1.0, 0, 2.0, 1.0) | ||
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| // Pitch shifted down one octave (0.5x pitch), ADSR envelope disabled | ||
| mix.SetFireWithPitch("sound.wav", time.Duration(0), 0, 1.0, 0, 0.5, 1.0) | ||
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| // Pitch shifted up a perfect fifth (~1.5x pitch), ADSR envelope disabled | ||
| mix.SetFireWithPitch("sound.wav", time.Duration(0), 0, 1.0, 0, 1.5, 1.0) | ||
| ``` | ||
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| ## API | ||
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| ```go | ||
| func SetFireWithPitch( | ||
| source string, // path to audio file | ||
| begin time.Duration, // start time | ||
| sustain time.Duration, // sustain duration (0 = play full file) | ||
| volume float64, // volume (0 to 1) | ||
| pan float64, // pan (-1 to +1) | ||
| pitch float64, // pitch multiplier (1.0 = no change) | ||
| timeStretch float64 // time stretch multiplier (currently unused) | ||
| ) *fire.Fire | ||
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| func SetFireWithPitchADSR( | ||
| source string, // path to audio file | ||
| begin time.Duration, // start time | ||
| sustain time.Duration, // sustain duration (0 = play full file) | ||
| volume float64, // volume (0 to 1) | ||
| pan float64, // pan (-1 to +1) | ||
| attack time.Duration, // ADSR: Attack time (0 = disabled) | ||
| decay time.Duration, // ADSR: Decay time (0 = disabled) | ||
| sustainLevel float64, // ADSR: Sustain level (0 to 1, use 1.0 to disable) | ||
| release time.Duration, // ADSR: Release time (0 = disabled) | ||
| pitch float64, // pitch multiplier (1.0 = no change) | ||
| timeStretch float64 // time stretch multiplier (currently unused) | ||
| ) *fire.Fire | ||
| ``` | ||
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| **Note:** `SetFireWithPitch()` uses default ADSR settings (no envelope effect). For full control over both pitch shifting and ADSR envelope, use `SetFireWithPitchADSR()`. | ||
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| ## Pitch Multiplier | ||
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| The `pitch` parameter is a multiplier: | ||
| - `1.0` = original pitch (no change) | ||
| - `2.0` = up one octave (twice the frequency) | ||
| - `0.5` = down one octave (half the frequency) | ||
| - `1.5` = up a perfect fifth | ||
| - `0.75` = down a perfect fourth | ||
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| ## How It Works | ||
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| The implementation uses sample-rate modification with linear interpolation: | ||
| - Higher pitch values increase playback speed (shorter duration) | ||
| - Lower pitch values decrease playback speed (longer duration) | ||
| - Linear interpolation between samples ensures smooth playback without artifacts | ||
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| ## Note on Time Stretching | ||
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| Currently, changing pitch also changes playback speed proportionally. True independent time-stretching (changing speed without affecting pitch) would require more advanced algorithms like phase vocoding or time-domain harmonic scaling, which may be added in future versions. | ||
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| ## Examples | ||
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| ### Pitch Shifting a Drum Loop | ||
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| ```go | ||
| // Play a drum loop at different pitches for variation | ||
| mix.SetFireWithPitch("drums.wav", 0*time.Second, 0, 1.0, 0, 1.0, 1.0) // original | ||
| mix.SetFireWithPitch("drums.wav", 4*time.Second, 0, 1.0, 0, 0.9, 1.0) // slightly lower | ||
| mix.SetFireWithPitch("drums.wav", 8*time.Second, 0, 1.0, 0, 1.1, 1.0) // slightly higher | ||
| ``` | ||
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| ### Creating Harmonies | ||
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| ```go | ||
| // Play the same sample at different pitches to create harmony | ||
| baseTime := 2 * time.Second | ||
| mix.SetFireWithPitch("note.wav", baseTime, 0, 0.8, -0.5, 1.0, 1.0) // root (left) | ||
| mix.SetFireWithPitch("note.wav", baseTime, 0, 0.8, 0, 1.25, 1.0) // major third (center) | ||
| mix.SetFireWithPitch("note.wav", baseTime, 0, 0.8, 0.5, 1.5, 1.0) // perfect fifth (right) | ||
| ``` | ||
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| ### Bass Drop Effect | ||
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| ```go | ||
| // Create a bass drop by pitch shifting down over time | ||
| for i := 0; i < 10; i++ { | ||
| pitch := 1.0 - float64(i)*0.1 // gradually lower pitch | ||
| mix.SetFireWithPitch("bass.wav", time.Duration(i)*200*time.Millisecond, | ||
| 200*time.Millisecond, 1.0, 0, pitch, 1.0) | ||
| } | ||
| ``` | ||
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| ### Combining Pitch Shift with ADSR Envelope | ||
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| ```go | ||
| // Use SetFireWithPitchADSR for full control over both pitch and envelope | ||
| attack := 100 * time.Millisecond | ||
| decay := 50 * time.Millisecond | ||
| sustainLevel := 0.7 | ||
| release := 200 * time.Millisecond | ||
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| mix.SetFireWithPitchADSR("synth.wav", 0, 2*time.Second, 1.0, 0, | ||
| attack, decay, sustainLevel, release, 1.5, 1.0) | ||
| ``` | ||
| ``` | ||
|
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