NAME
SoVRMLAudioClip -
The SoVRMLAudioClip class is used to load and store audio data.
Audio data is loaded using the simage library, so make sure you have
built the simage library with support for the audio file formats you
intend to use (libogg, libvorbis and libvorbisfile for OggVorbis,
libsndfile for WAV and several other formats).
SYNOPSIS
#include <Inventor/VRMLnodes/SoVRMLAudioClip.h>
Inherits SoNode.
Public Types
typedef void * open_func (const SbStringList &url, SoVRMLAudioClip
*clip, void *userdataptr)
typedef size_t read_func (void *datasource, void *buffer, int
numframes, int &channels, SoVRMLAudioClip *clip, void *userdataptr)
typedef int seek_func (void *datasource, long offset, int whence,
SoVRMLAudioClip *clip, void *userdataptr)
typedef long tell_func (void *datasource, SoVRMLAudioClip *clip, void
*userdataptr)
typedef int close_func (void *datasource, SoVRMLAudioClip *clip, void
*userdataptr)
Public Member Functions
SoVRMLAudioClip (void)
int getSampleRate ()
void * open (const SbStringList &url)
size_t read (void *datasource, void *buffer, int numframes, int
&channels)
int seek (void *datasource, long offset, int whence)
long tell (void *datasource)
int close (void *datasource)
void setCallbacks (open_func *opencb, read_func *readcb, seek_func
*seekcb, tell_func *tellcb, close_func *closecb, void *userdataptr)
Static Public Member Functions
static void initClass (void)
static void setSubdirectories (const SbList< SbString >
&subdirectories)
static const SbStringList & getSubdirectories ()
static void setDefaultPauseBetweenTracks (SbTime pause)
static SbTime getDefaultPauseBetweenTracks ()
static void setDefaultIntroPause (SbTime pause)
static SbTime getDefaultIntroPause ()
static void setDefaultSampleRate (int samplerate)
static int getDefaultSampleRate ()
static void setDefaultTimerInterval (SbTime interval)
static SbTime getDefaultTimerInterval ()
Public Attributes
SoSFString description
SoSFBool loop
SoSFFloat pitch
SoSFTime startTime
SoSFTime stopTime
SoMFString url
Protected Member Functions
virtual ~SoVRMLAudioClip ()
Protected Attributes
SoSFTime duration_changed
SoSFBool isActive
Detailed Description
The SoVRMLAudioClip class is used to load and store audio data.
Audio data is loaded using the simage library, so make sure you have
built the simage library with support for the audio file formats you
intend to use (libogg, libvorbis and libvorbisfile for OggVorbis,
libsndfile for WAV and several other formats).
The detailed class documentation is taken verbatim from the VRML97
standard (ISO/IEC 14772-1:1997). It is copyright The Web3D Consortium,
and is used by permission of the Consortium:
AudioClip {
exposedField SFString description ""
exposedField SFBool loop FALSE
exposedField SFFloat pitch 1.0 # (0, inf)
exposedField SFTime startTime 0 # (-inf, inf)
exposedField SFTime stopTime 0 # (-inf, inf)
exposedField MFString url []
eventOut SFTime duration_changed
eventOut SFBool isActive
}
.fi
An AudioClip node specifies audio data that can be referenced by Sound nodes. The description field specifies a textual description of the audio source. A browser is not required to display the description field but may choose to do so in addition to playing the sound. The url field specifies the URL from which the sound is loaded. Browsers shall support at least the wavefile format in uncompressed PCM format (see http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-VRML97/part1/bibliography.html#[WAV]). It is recommended that browsers also support the MIDI file type 1 sound format (see http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-VRML97/part1/references.html#[MIDI]); MIDI files are presumed to use the General MIDI patch set. Subclause 4.5, VRML and the World Wide Web (<http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-VRML97/part1/concepts.html#4.5>), contains details on the url field. The results are undefined when no URLs refer to supported data types.
The loop, startTime, and stopTime exposedFields and the isActive eventOut, and their effects on the AudioClip node, are discussed in detail in 4.6.9, Time-dependent nodes (<http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-VRML97/part1/concepts.html#4.6.9>). The ’cycle’ of an AudioClip is the length of time in seconds for one playing of the audio at the specified pitch. The pitch field specifies a multiplier for the rate at which sampled sound is played. Values for the pitch field shall be greater than zero. Changing the pitch field affects both the pitch and playback speed of a sound. A set_pitch event to an active AudioClip is ignored and no pitch_changed eventOut is generated. If pitch is set to 2.0, the sound shall be played one octave higher than normal and played twice as fast. For a sampled sound, the pitch field alters the sampling rate at which the sound is played. The proper implementation of pitch control for MIDI (or other note sequence sound clips) is to multiply the tempo of the playback by the pitch value and adjust the MIDI Coarse Tune and Fine Tune controls to achieve the proper pitch change. A duration_changed event is sent whenever there is a new value for the ’normal’ duration of the clip. Typically, this will only occur when the current url in use changes and the sound data has been loaded, indicating that the clip is playing a different sound source. The duration is the length of time in seconds for one cycle of the audio for a pitch set to 1.0. Changing the pitch field will not trigger a duration_changed event. A duration value of ’-1’ implies that the sound data has not yet loaded or the value is unavailable for some reason. A duration_changed event shall be generated if the AudioClip node is loaded when the VRML file is read or the AudioClip node is added to the scene graph. The isActive eventOut may be used by other nodes to determine if the clip is currently active. If an AudioClip is active, it shall be playing the sound corresponding to the sound time (i.e., in the sound’s local time system with sample 0 at time 0):
t = (now - startTime) modulo (duration / pitch)
Constructor & Destructor Documentation
SoVRMLAudioClip::SoVRMLAudioClip (void) Constructor.
SoVRMLAudioClip::~SoVRMLAudioClip () [protected, virtual] Destructor.
Member Function Documentation
void SoVRMLAudioClip::initClass (void) [static] Sets up initialization for
data common to all instances of this class, like submitting necessary
information to the Coin type system.
Reimplemented from SoNode.
void * SoVRMLAudioClip::open (const SbStringList & urlref) Opens an audio
source with the given url. Returns a handle to the datasource.
size_t SoVRMLAudioClip::read (void * datasource, void * buffer, int
numframes, int & channels) Reads numframes frames of audio with
channels channels from datasource into buffer. Buffer must be allocated
by the caller, and must be able to hold all the audio data (size =
numframes * channels * sizeof(int16_t)). The function must always fill
the buffer completely unless buffer == NULL.
When an error occurs, or when end-of-file has been reached, this
function returns 0. Otherwise, the function should return numframes.
When the caller receives a return value of 0, it will queue the
returned buffer for playing. When this buffer is finished playing, the
caller will call read() one final time, with buffer == NULL. The read()
function can then set the isActive field to FALSE, free any resources
allocated, etc.
int SoVRMLAudioClip::seek (void * datasource, long offset, int whence)
Moves the ’filepointer’ in the datasource, returns -1L on error.
long SoVRMLAudioClip::tell (void * datasource) Returns the current position
of the ’filepointer’ in the datasource, or -1L on error.
int SoVRMLAudioClip::close (void * datasource) Closes datasource.
void SoVRMLAudioClip::setCallbacks (open_func * opencb, read_func * readcb,
seek_func * seekcb, tell_func * tellcb, close_func * closecb, void *
userdataptr) Sets callbacks for opening, reading, seeking, telling and
closing an audio source. Specifying NULL for a function is OK, except
for the read function. If a function set to NULL is later called, a
default implementation doing nothing is called in it’s place.
Member Data Documentation
SoSFString SoVRMLAudioClip::description Description of the audio clip.
Default value is an empty string.
SoSFBool SoVRMLAudioClip::loop Specifies whether sound should be looped. Is
FALSE by default.
SoSFFloat SoVRMLAudioClip::pitch Specifies the pitch. The default value is
1.0.
Alters the sampling rate at which the sound is played. A pitch of 2.0
means that the sound should be played twice as fast and one octave
higher than normal.
SoSFTime SoVRMLAudioClip::startTime Specifies the start time. Default value
is 0.
SoSFTime SoVRMLAudioClip::stopTime Specifies the stop time. Default value
is 0.
SoMFString SoVRMLAudioClip::url The audio data URL.
SoVRMLAudioClip::duration_changed [protected] An eventOut sent when a new
sound starts playing.
SoVRMLAudioClip::isActive [protected] This eventOut is sent when the sound
starts/stops playing.
Author
Generated automatically by Doxygen for Coin from the source code.