daisy::WavPlayer< workspace_bytes > Class Template Reference

Detailed Description

template<size_t workspace_bytes>
class daisy::WavPlayer< workspace_bytes >

WAV file Streaming Playback

At this time, this class only supports streaming of 16-bit WAV Files The output of this class will be in float converted from 16-bit integers and linearly interpolated for non-integer playback speeds.

Due to the implementation, reverse playback is not possible with this class.

The workspace_bytes template parameter is used to set the size in bytes of audio samples within the FIFO.

The bulk of amount of memory used by this class is approximately: (2 * workspace_bytes); This could hypothetically be reduced by half by directly accessing the FIFO's inner array (requires modifications to FIFO class), or making a new type of queue data structure

Whenever the Stream function results in a the samples FIFO being less than 75% full, it will generate a request for new data. So the average disk i/o transaction will be the workspace_bytes / 4. However, There are times, like when restarting playback, or opening a different file, that will trigger the entire buffer to be filled.

#include <WavPlayer.h>

Classes
struct	FileInfo

Public Types
enum class	Result {   Ok , FileNotFoundError , PlaybackUnderrun , PrepareOverrun ,   NewSamplesRequested , DiskError }

Public Member Functions
	WavPlayer ()
	~WavPlayer ()
Result	Init (const char *name)
Result	Open (const char *name)
Result	Close ()
Result	Prepare ()
Result	Stream (float *samples, size_t num_channels)
void	Restart ()
size_t	GetDurationInSamples () const
size_t	GetChannels () const
uint32_t	GetPosition () const
float	GetNormalizedPosition () const
void	SetLooping (bool state)
bool	GetLooping () const
void	SetPlaying (bool state)
bool	GetPlaying () const
void	SetPlaybackSpeedRatio (const float speed)
void	SetPlaybackSpeedSemitones (const float semitones)

Member Enumeration Documentation

Result

template<size_t workspace_bytes>

enum class daisy::WavPlayer::Result

strong

Return values for status, and errors.

Enumerator
Ok
FileNotFoundError
PlaybackUnderrun
PrepareOverrun
NewSamplesRequested
DiskError

Constructor & Destructor Documentation

WavPlayer()

template<size_t workspace_bytes>

daisy::WavPlayer< workspace_bytes >::WavPlayer ( )

inline

~WavPlayer()

template<size_t workspace_bytes>

daisy::WavPlayer< workspace_bytes >::~WavPlayer ( )

inline

Member Function Documentation

Close()

template<size_t workspace_bytes>

Result daisy::WavPlayer< workspace_bytes >::Close ( )

inline

Close a file, and clear the data

GetChannels()

template<size_t workspace_bytes>

size_t daisy::WavPlayer< workspace_bytes >::GetChannels ( ) const

inline

Return the number of audio channels in the open audio file

GetDurationInSamples()

template<size_t workspace_bytes>

size_t daisy::WavPlayer< workspace_bytes >::GetDurationInSamples ( ) const

inline

Return the number of samples in the open audio file

GetLooping()

template<size_t workspace_bytes>

bool daisy::WavPlayer< workspace_bytes >::GetLooping ( ) const

inline

Return whether the player is looping or not.

GetNormalizedPosition()

template<size_t workspace_bytes>

float daisy::WavPlayer< workspace_bytes >::GetNormalizedPosition ( ) const

inline

Returns a 0-1 representation of the playhead position within the file.

GetPlaying()

template<size_t workspace_bytes>

bool daisy::WavPlayer< workspace_bytes >::GetPlaying ( ) const

inline

GetPosition()

template<size_t workspace_bytes>

uint32_t daisy::WavPlayer< workspace_bytes >::GetPosition ( ) const

inline

Returns the position of the playhead in samples from the start of the file

Init()

template<size_t workspace_bytes>

Result daisy::WavPlayer< workspace_bytes >::Init ( const char * name )

inline

Initialize, and open a single file by name for playback

Open the file

Open()

template<size_t workspace_bytes>

Result daisy::WavPlayer< workspace_bytes >::Open ( const char * name )

inline

Open a file, and prepare audio for streaming

Prepare()

template<size_t workspace_bytes>

Result daisy::WavPlayer< workspace_bytes >::Prepare ( )

inline

To be executed in the main while loop, or other interruptable areas of code. This will perform the actual Disk I/O for streaming audio into the buffers used for playback.

Restart()

template<size_t workspace_bytes>

void daisy::WavPlayer< workspace_bytes >::Restart ( )

inline

Clear all playback samples, and return to the beginning of the audio file immediately

SetLooping()

template<size_t workspace_bytes>

void daisy::WavPlayer< workspace_bytes >::SetLooping ( bool state )

inline

Set whether the audio file will automatically continue playing from the beginning after reaching the end of file.

SetPlaybackSpeedRatio()

template<size_t workspace_bytes>

void daisy::WavPlayer< workspace_bytes >::SetPlaybackSpeedRatio ( const float speed )

inline

Direct setter of playback speed as a ratio compared to original speed. For example, 1.0 equals original speed, 0.5 is half-speed, etc.

SetPlaybackSpeedSemitones()

template<size_t workspace_bytes>

void daisy::WavPlayer< workspace_bytes >::SetPlaybackSpeedSemitones ( const float semitones )

inline

Sets playback speed as a number of semitones offset from original pitch For example, +7 a ratio of 1.5, +12 a ratio of 2, -12 a ratio of 0.5, etc.

SetPlaying()

template<size_t workspace_bytes>

void daisy::WavPlayer< workspace_bytes >::SetPlaying ( bool state )

inline

Stream()

template<size_t workspace_bytes>

Result daisy::WavPlayer< workspace_bytes >::Stream ( float * samples, size_t num_channels )

inline

Stream Audio from disk at the current playback speed.

Each call to this will increment the playback position's internal accumulator by the playback speed. Anytime this accumulator exceeds 1.0, it will update it's position tracker, and pop the next sample from the FIFO of audio samples. Whenever the contents of the audio sample FIFO fall below 75% of it's capacity, a request is generated to refill it. The maximum playback speed possible is limited to the following factors:

• SD Card Bus-width
• SD Card Clock Speed
• workspace_bytes setting (consequently, transfer sizes)

It is possible to allow higher playback speeds, and improve bandwidth by using higher workspace sizes, with the trade-offs being memory, and latency with certain transactions.

Parameters

samples	buffer of floats to fill with audio samples from disk
num_channels	number of channels provided to fill. This can be different from the number of channels in the file.

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The documentation for this class was generated from the following file:

• src/util/WavPlayer.h