OpenAL Data

2-Apr-1999

   This is the page is dedicated to expose OpenAL's data types, values and such.


Basic Types

2-Apr-1999

   This is a definition of all the basic types that will be used in the library. This is, so far, just my initiative. Please, comment on it.

typedef signed int ALint;     /* machine-dependent signed integer value */
typedef signed char ALint8;   /* 8-bit signed integer value */
typedef signed short ALint16; /* 16-bit signed integer value */
typedef signed long ALint32;  /* 32-bit signed integer value */

typedef unsigned int ALuint;     /* machine-dependent unsigned integer value */
typedef unsigned char ALuint8;   /* 8-bit unsigned integer value */
typedef unsigned short ALuint16; /* 16-bit unsigned integer value */
typedef unsigned long ALuint32;  /* 32-bit unsigned integer value */

typedef float ALfloat32; /* 32-bit floating point value */

typedef enum { ALfalse, ALtrue } ALbool; /* Used to specify a boolean value */

typedef ALuint32 ALbitfield; /* Used to specify a bit field or a bit mask value */


Volume values

2-Apr-1999

   This is a definition of the values that will be used to specify sound volumes. This is, so far, just my initiative. Please, comment on it.

   Linear volume values are defined as 10000 for full volume, and 0 for silence. Values above 10000 are allowed, and represent volume overloading. Linear volumes can be integer or floating point.

   DB volume values are defined as 0 for full volume, -600 for half volume, -1200 for quarter volume and -10000 for silence. Positive values are legal, and represent overloading. DB volumes can be integer or floating point.

   Volume overloading consists in specifying a volume that's higher than the full volume. This allows for an extra 'punch' and, sometimes, for extra output quality, at the cost of possible distortion.

#define AL_DOUBLEVOLUME_LINEAR 20000
#define AL_FULLVOLUME_LINEAR   10000
#define AL_HALFVOLUME_LINEAR    5000
#define AL_SILENCE_LINEAR          0

#define AL_DOUBLEVOLUME_DB    600
#define AL_FULLVOLUME_DB        0
#define AL_HALFVOLUME_DB     -600
#define AL_SILENCE_DB      -10000


Frequency values

2-Apr-1999

   This is a definition of the values that will be used to specify sound frequencies, sample rates, notes, pitch, etc... This is, so far, just my initiative. Please, comment on it.

   Sample rate frequency values are defined as samples per second. They can be integer or floating point.

   Note frequency values are defined as integers composed of an octave value and a halftone value. They can only be integer. For example:

AL_HALFTONE_C_SHARP + AL_OCTAVE_3

   Relative frequency values are defined as multipliers for an existing frequency value, 10000 for unchanged frequency. They can be integer or floating point. For example, 20000 is double frequency (double sample rate), and 5000 is half the frequency.

#define AL_OCTAVE_0 (12*0)
#define AL_OCTAVE_1 (12*1)
#define AL_OCTAVE_2 (12*2)
#define AL_OCTAVE_3 (12*3)
#define AL_OCTAVE_4 (12*4)
#define AL_OCTAVE_5 (12*5)
#define AL_OCTAVE_6 (12*6)
#define AL_OCTAVE_7 (12*7)

#define AL_HALFTONE_C        0
#define AL_HALFTONE_C_SHARP  1
#define AL_HALFTONE_D_FLAT   1
#define AL_HALFTONE_D        2
#define AL_HALFTONE_D_SHARP  3
#define AL_HALFTONE_E_FLAT   3
#define AL_HALFTONE_E        4
#define AL_HALFTONE_F        5
#define AL_HALFTONE_F_SHARP  6
#define AL_HALFTONE_G_FLAT   6
#define AL_HALFTONE_G        7
#define AL_HALFTONE_G_SHARP  8
#define AL_HALFTONE_A_FLAT   8
#define AL_HALFTONE_A        9
#define AL_HALFTONE_A_SHARP 10
#define AL_HALFTONE_B_FLAT  10
#define AL_HALFTONE_B       11

#define AL_MIDDLE_C (AL_OCTAVE_3 + AL_HALFTONE_C)

#define AL_FREQUENCY_DOUBLE 20000
#define AL_FREQUENCY_IDENT  10000
#define AL_FREQUENCY_HALF    5000


Panning values

2-Apr-1999

   This is a definition of the values that will be used to specify stereo sound panning. This is, so far, just my initiative. Please, comment on it.

   Panning is defined as a position in a 360-degree circumference around the listener. Values are defined as unsigned, 16-bit integers, with values:

  • 0 defines a centered sound in front of the listener
  • 8192 defines full-right
  • 16384 defines full-behind
  • 24576 defines full-left
  • 32768 defines an inverted centered sound in front of the listener
  • 40960 defines inverted full-right
  • 49152 defines inverted full-behind
  • 57344 defines inverted full-left

   Inverted values are used in case simple surround is actually used. Because of the wave-inversion nature of its implementation, there are two possible solutions for each position around the listener. Reserving different values for both solutions allows for smooth surround panning-shift. Using 32-bit values to represent panning allows for specification of full turns around the listener, good for some dizzying panning-shift effects.

#define AL_PANNING_CENTER         0
#define AL_PANNING_RIGHT       8192
#define AL_PANNING_BEHIND     16384
#define AL_PANNING_LEFT       24576
#define AL_PANNING_CENTER_INV 32768
#define AL_PANNING_RIGHT_INV  40960
#define AL_PANNING_BEHIND_INV 49152
#define AL_PANNING_LEFT_INV   57344


Time values

2-Apr-1999

   This is a definition of the values that will be used to specify a time interval. This is, so far, just my initiative. Please, comment on it.

   Millisecond time values define a time interval as an elapsed number of milliseconds. They can be integer or floating point. Infinite time can be specified as -1.

#define AL_MILLISEC_INFINITE   -1


Position values

2-Apr-1999

   This is a definition of the values that will be used to specify a position within a sound. This is, so far, just my initiative. Please, comment on it.

   Sample position values are defined as the index of a sample within a wave sound. They can be integer or floating point. A value of 0 is the beginning of the sound, and a value of -1 is used to mean the end of the sound. They are usually specified as unsigned integers, so AL_SAMPLE_POSITION_END needs to be cast to the appropriate type.

   Time position values are defined as a time value elapsed from the beginning of the sound. They can be specified as any type of time value.

#define AL_SAMPLE_POSITION_BEGINNING              0
#define AL_SAMPLE_POSITION_END_INT    ((ALuint32)-1)
#define AL_SAMPLE_POSITION_END_FLOAT ((ALfloat32)-1)


Priority values

2-Apr-1999

   This is a definition of the values that will be used to specify sound priorities. This is, so far, just my initiative. Please, comment on it.

   Priorities are defined as 8-bit integers between 0 and 255. A value of 0 is the highest priority, and a value of 255 is the lowest priority. The meaning of each value, apart for its position in the 0-255 range, is completely application-dependent.

#define AL_PRIORITY_HIGHEST   0
#define AL_PRIORITY_NORMAL  128
#define AL_PRIORITY_LOWEST  255



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Last updated: 04 Apr 1999