Class daisy::WavPlayer¶

template <size_t workspace_bytes>

ClassList > daisy > WavPlayer

#include <WavPlayer.h>

Classes¶

Type	Name
struct	FileInfo

Public Types¶

Type	Name
enum	Result

Public Functions¶

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

Detailed Description¶

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.

Public Types Documentation¶

enum Result¶

enum daisy::WavPlayer::Result {
    Ok,
    FileNotFoundError,
    PlaybackUnderrun,
    PrepareOverrun,
    NewSamplesRequested,
    DiskError
};

Return values for status, and errors.

Public Functions Documentation¶

function Close¶

inline Result daisy::WavPlayer::Close ()

Close a file, and clear the data

function GetChannels¶

inline size_t daisy::WavPlayer::GetChannels () const

Return the number of audio channels in the open audio file

function GetDurationInSamples¶

inline size_t daisy::WavPlayer::GetDurationInSamples () const

Return the number of samples in the open audio file

function GetLooping¶

inline bool daisy::WavPlayer::GetLooping () const

Return whether the player is looping or not.

function GetNormalizedPosition¶

inline float daisy::WavPlayer::GetNormalizedPosition () const

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

function GetPlaying¶

inline bool daisy::WavPlayer::GetPlaying () const

function GetPosition¶

inline uint32_t daisy::WavPlayer::GetPosition () const

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

function Init¶

inline Result daisy::WavPlayer::Init (
    const  char * name
)

Initialize, and open a single file by name for playback

function Open¶

inline Result daisy::WavPlayer::Open (
    const  char * name
)

Open a file, and prepare audio for streaming

function Prepare¶

inline Result daisy::WavPlayer::Prepare ()

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.

function Restart¶

inline void daisy::WavPlayer::Restart ()

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

function SetLooping¶

inline void daisy::WavPlayer::SetLooping (
    bool state
)

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

function SetPlaybackSpeedRatio¶

inline void daisy::WavPlayer::SetPlaybackSpeedRatio (
    const  float speed
)

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.

function SetPlaybackSpeedSemitones¶

inline void daisy::WavPlayer::SetPlaybackSpeedSemitones (
    const  float semitones
)

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.

function SetPlaying¶

inline void daisy::WavPlayer::SetPlaying (
    bool state
)

function Stream¶

inline Result daisy::WavPlayer::Stream (
    float * samples,
    size_t num_channels
)

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.

function WavPlayer¶

inline daisy::WavPlayer::WavPlayer ()

function ~WavPlayer¶

inline daisy::WavPlayer::~WavPlayer ()

The documentation for this class was generated from the following file external-docs/libDaisy/src/util/WavPlayer.h