PitchShift.h File Reference

Real-time pitch shifting audio effect implementation. More...

#include <math.h>
#include <stdio.h>
#include <string.h>
#include "AudioTools/CoreAudio/AudioOutput.h"
#include "AudioTools/CoreAudio/AudioTypes.h"
#include "AudioToolsConfig.h"

Go to the source code of this file.

Classes
struct	PitchShiftInfo
	Configuration for PitchShiftOutput. More...
class	PitchShiftOutput< T, BufferT >
	Real-time pitch shifting audio effect. More...
class	VariableSpeedRingBuffer< T >
	Optimized buffer implementation for pitch shifting with interpolation. More...
class	VariableSpeedRingBuffer180< T >
	Variable speed ring buffer with 180-degree phase shifting. More...
class	VariableSpeedRingBufferSimple< T >
	Very Simple Buffer implementation for Pitch Shift. More...

Namespaces
namespace	audio_tools
	Generic Implementation of sound input and output for desktop environments using portaudio.

Detailed Description

Real-time pitch shifting audio effect implementation.

This file contains classes for performing real-time pitch shifting on audio streams. Pitch shifting changes the frequency (pitch) of audio without affecting its duration, allowing for creative audio effects like chipmunk voices, deeper bass tones, or musical pitch correction.

The implementation provides three different buffer algorithms with varying quality and computational complexity:

1. VariableSpeedRingBufferSimple: Basic implementation with potential artifacts
   • Fastest processing
   • Suitable for simple applications where quality is not critical
   • May produce audible artifacts during buffer overruns
2. VariableSpeedRingBuffer180: Advanced implementation with 180° phase offset
   • Good quality with moderate complexity
   • Uses dual read pointers with cross-fading to reduce artifacts
   • Based on STM32 DSP techniques
3. VariableSpeedRingBuffer: Premium implementation with interpolation
   • Highest quality with advanced features
   • Linear interpolation for smooth sample transitions
   • Automatic phase alignment during pointer collisions
   • Best for professional audio applications

Note

Pitch shifting introduces some latency due to buffering. Buffer size affects both quality and latency - larger buffers provide better quality but more delay.

Author

Phil Schatzmann

Copyright

GPLv3