Real-time pitch shifting audio effect. More...
#include <PitchShift.h>
Public Member Functions | |
| PitchShiftOutput (Print &out) | |
| Constructor. | |
| virtual void | addNotifyAudioChange (AudioInfoSupport &bi) |
| Adds target to be notified about audio changes. | |
| virtual AudioInfo | audioInfo () override |
| provides the actual input AudioInfo | |
| virtual AudioInfo | audioInfoOut () |
| virtual int | availableForWrite () override |
| bool | begin () |
| Initialize pitch shifting with current configuration. | |
| virtual bool | begin (AudioInfo info) |
| bool | begin (PitchShiftInfo info) |
| Initialize pitch shifting with configuration. | |
| virtual void | clearNotifyAudioChange () |
| Deletes all change notify subscriptions. | |
| PitchShiftInfo | defaultConfig () |
| Get default configuration for pitch shifting. | |
| void | end () |
| Stop pitch shifting and deactivate the effect. | |
| virtual void | flush () |
| virtual bool | isDeletable () |
| If true we need to release the related memory in the destructor. | |
| bool | isNotifyActive () |
| Checks if the automatic AudioInfo update is active. | |
| virtual | operator bool () |
| virtual bool | removeNotifyAudioChange (AudioInfoSupport &bi) |
| Removes a target in order not to be notified about audio changes. | |
| virtual void | setAudioInfo (AudioInfo newInfo) override |
| Defines the input AudioInfo. | |
| void | setNotifyActive (bool flag) |
| Deactivate/Reactivate automatic AudioInfo updates: (default is active) | |
| size_t | write (const uint8_t *data, size_t len) override |
| Process and write audio data with pitch shifting applied. | |
| virtual size_t | write (uint8_t ch) override |
| virtual void | writeSilence (size_t len) |
Protected Member Functions | |
| void | notifyAudioChange (AudioInfo info) |
| T | pitchShift (T value) |
| Execute pitch shift on a single sample. | |
Protected Attributes | |
| int | _timeout = 10 |
| bool | active = false |
| Whether pitch shifting is currently active. | |
| BufferT | buffer |
| Variable speed buffer for pitch shifting. | |
| PitchShiftInfo | cfg |
| Current configuration. | |
| bool | is_active = false |
| bool | is_notify_active = true |
| Vector< AudioInfoSupport * > | notify_vector |
| Print * | p_out = nullptr |
| Output stream for processed audio. | |
| SingleBuffer< uint8_t > | tmp {MAX_SINGLE_CHARS} |
| int | tmpPos = 0 |
Detailed Description
Real-time pitch shifting audio effect.
This class implements real-time pitch shifting that changes the frequency of audio without affecting its duration. It can shift pitch up or down while maintaining the original playback speed. The implementation:
- Reduces multi-channel audio to mono for processing
- Applies pitch shifting using a configurable buffer algorithm
- Outputs the shifted audio in the original channel configuration
The pitch shifting is accomplished using a variable-speed ring buffer that reads at different rates than it writes. Three buffer implementations are available:
- VariableSpeedRingBufferSimple: Basic implementation with potential artifacts
- VariableSpeedRingBuffer180: Uses 180° phase shifting to reduce artifacts
- VariableSpeedRingBuffer: Advanced implementation with interpolation and phase restoration
- Note
- Pitch shifting is a complex DSP operation that requires buffering, which introduces some latency. The buffer size affects both quality and latency.
- Template Parameters
-
T Sample data type (int16_t, int32_t, float, etc.) BufferT Buffer implementation type (one of the VariableSpeedRingBuffer variants)
Constructor & Destructor Documentation
◆ PitchShiftOutput()
Constructor.
- Parameters
-
out Reference to the output stream where processed audio will be written
Member Function Documentation
◆ addNotifyAudioChange()
|
inlinevirtualinherited |
Adds target to be notified about audio changes.
Reimplemented in CodecNOP, EncodedAudioOutput, EncodedAudioStream, AACDecoderFDK, DecoderBasic, CodecChain, MP3DecoderHelix, MP3DecoderMAD, OggContainerDecoder, RTSPClient< TcpClient, UdpSocket >, Pipeline, and Pipeline::ModifyingStreamAdapter.
◆ audioInfo()
provides the actual input AudioInfo
Implements AudioInfoSupport.
Reimplemented in AdapterPrintToAudioOutput, EncodedAudioOutput, and AdapterAudioStreamToAudioOutput.
◆ audioInfoOut()
provides the actual output AudioInfo: this is usually the same as audioInfo() unless we use a transforming stream
Reimplemented in PureDataStream, PWMAudioOutput, ChannelFormatConverterStreamT< T >, ChannelFormatConverterStream, NumberFormatConverterStreamT< TFrom, TTo >, NumberFormatConverterStream, FormatConverterStream, Pipeline, ResampleStream, and ResampleStreamT< TInterpolator >.
◆ availableForWrite()
Reimplemented from Print.
Reimplemented in AudioESP32ULP, RTSPOutput< Platform >, EncodedAudioOutput, AudioServerEx, AudioSyncWriter, AdapterAudioStreamToAudioOutput, CsvOutput< T >, MemoryOutput, and PWMAudioOutput.
◆ begin() [1/3]
Initialize pitch shifting with current configuration.
- Returns
- true if initialization successful
Reimplemented from AudioOutput.
◆ begin() [2/3]
Reimplemented in AudioESP32ULP, RTSPOutput< Platform >, RTTTLOutput< T >, ChannelsSelectOutput, CsvOutput< T >, and EncodedAudioOutput.
◆ begin() [3/3]
Initialize pitch shifting with configuration.
- Parameters
-
info Configuration containing pitch_shift factor, buffer_size, and audio format
- Returns
- true if initialization successful
◆ clearNotifyAudioChange()
Deletes all change notify subscriptions.
Reimplemented in RTSPClient< TcpClient, UdpSocket >.
◆ defaultConfig()
|
inline |
Get default configuration for pitch shifting.
- Returns
- PitchShiftInfo with default values appropriate for type T
◆ end()
Stop pitch shifting and deactivate the effect.
Reimplemented from AudioOutput.
◆ flush()
Reimplemented from Print.
Reimplemented in MultiOutput, and HexDumpOutput.
◆ isDeletable()
If true we need to release the related memory in the destructor.
Reimplemented in AdapterPrintToAudioOutput, and AdapterAudioStreamToAudioOutput.
◆ isNotifyActive()
◆ notifyAudioChange()
◆ operator bool()
Reimplemented in RTSPOutput< Platform >, EncodedAudioOutput, and AdapterAudioStreamToAudioOutput.
◆ pitchShift()
Execute pitch shift on a single sample.
This method performs the core pitch shifting operation by writing the input sample to the buffer and reading back the pitch-shifted result. The time difference between write and read operations, controlled by the buffer's increment factor, creates the pitch shift effect.
- Parameters
-
value Input sample value
- Returns
- Pitch-shifted sample value
◆ removeNotifyAudioChange()
|
inlinevirtualinherited |
Removes a target in order not to be notified about audio changes.
Reimplemented in RTSPClient< TcpClient, UdpSocket >.
◆ setAudioInfo()
Defines the input AudioInfo.
Implements AudioInfoSupport.
Reimplemented in ChannelsSelectOutput, AdapterPrintToAudioOutput, MultiOutput, AdapterAudioStreamToAudioOutput, CsvOutput< T >, PWMAudioOutput, and EncodedAudioOutput.
◆ setNotifyActive()
Deactivate/Reactivate automatic AudioInfo updates: (default is active)
◆ write() [1/2]
Process and write audio data with pitch shifting applied.
This method processes the input audio by:
- Converting multi-channel samples to mono by averaging
- Applying pitch shifting to the mono signal
- Duplicating the processed signal to all output channels
- Parameters
-
data Pointer to input audio data len Number of bytes to process
- Returns
- Number of bytes written to output
Implements AudioOutput.
◆ write() [2/2]
Reimplemented in MetaDataOutput, and MultiOutput.
◆ writeSilence()
Writes n 0 values (= silence)
- Parameters
-
len
Member Data Documentation
◆ _timeout
|
protectedinherited |
◆ active
Whether pitch shifting is currently active.
◆ buffer
Variable speed buffer for pitch shifting.
◆ cfg
|
protected |
Current configuration.
◆ is_active
◆ is_notify_active
◆ notify_vector
|
protectedinherited |
◆ p_out
Output stream for processed audio.
◆ tmp
|
protectedinherited |
◆ tmpPos
|
protectedinherited |
The documentation for this class was generated from the following file:
- src/AudioTools/CoreAudio/AudioEffects/PitchShift.h
