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Update OpenAL Soft to commit 414b56edec5441211dc924fef365c54267c04f1c

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Alex Szpakowski
2018-04-03 20:46:26 -03:00
parent ac70ec9f6f
commit 5be7c968b8
138 changed files with 18084 additions and 18482 deletions
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libs/openal-soft/docs/hrtf.txt
+35 -25
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@@ -29,22 +29,31 @@ rates, for example.
The file format is specified below. It uses little-endian byte order.
==
ALchar magic[8] = "MinPHR01";
ALchar magic[8] = "MinPHR02";
ALuint sampleRate;
ALubyte sampleType; /* Can be 0 (16-bit) or 1 (24-bit). */
ALubyte channelType; /* Can be 0 (mono) or 1 (stereo). */
ALubyte hrirSize; /* Can be 8 to 128 in steps of 8. */
ALubyte fdCount; /* Can be 1 to 16. */
ALubyte hrirSize; /* Can be 8 to 128 in steps of 8. */
ALubyte evCount; /* Can be 5 to 128. */
struct {
ALushort distance; /* Can be 50mm to 2500mm. */
ALubyte evCount; /* Can be 5 to 128. */
ALubyte azCount[evCount]; /* Each can be 1 to 128. */
} fields[fdCount];
ALubyte azCount[evCount]; /* Each can be 1 to 128. */
/* NOTE: hrirCount is the sum of all azCounts */
ALshort coefficients[hrirCount][hrirSize];
ALubyte delays[hrirCount]; /* Each can be 0 to 63. */
/* NOTE: ALtype can be ALshort (16-bit) or ALbyte[3] (24-bit) depending on
* sampleType,
* hrirCount is the sum of all azCounts.
* channels can be 1 (mono) or 2 (stereo) depending on channelType.
*/
ALtype coefficients[hrirCount][hrirSize][channels];
ALubyte delays[hrirCount][channels]; /* Each can be 0 to 63. */
==
The data is described as thus:
The file first starts with the 8-byte marker, "MinPHR01", to identify it as an
The file first starts with the 8-byte marker, "MinPHR02", to identify it as an
HRTF data set. This is followed by an unsigned 32-bit integer, specifying the
sample rate the data set is designed for (OpenAL Soft will not use it if the
output device's playback rate doesn't match).
@@ -52,23 +61,24 @@ output device's playback rate doesn't match).
Afterward, an unsigned 8-bit integer specifies how many sample points (or
finite impulse response filter coefficients) make up each HRIR.
The following unsigned 8-bit integer specifies the number of elevations used
by the data set. The elevations start at the bottom (-90 degrees), and
increment upwards. Following this is an array of unsigned 8-bit integers, one
for each elevation which specifies the number of azimuths (and thus HRIRs) that
make up each elevation. Azimuths start clockwise from the front, constructing
a full circle for the left ear only. The right ear uses the same HRIRs but in
reverse (ie, left = angle, right = 360-angle).
The following unsigned 8-bit integer specifies the number of fields used by the
data set. Then for each field an unsigned 16-bit short specifies the distance
for that field (in millimeters), followed by an 8-bit integer for the number of
elevations. These elevations start at the bottom (-90 degrees), and increment
upwards. Following this is an array of unsigned 8-bit integers, one for each
elevation which specifies the number of azimuths (and thus HRIRs) that make up
each elevation. Azimuths start clockwise from the front, constructing a full
circle. Mono HRTFs use the same HRIRs for both ears by reversing the azimuth
calculation (ie. left = angle, right = 360-angle).
The actual coefficients follow. Each coefficient is a signed 16-bit sample,
with each HRIR being a consecutive number of sample points. The HRIRs must be
minimum-phase. This allows the use of a smaller filter length, reducing
computation. For reference, the built-in data set uses a 32-point filter while
The actual coefficients follow. Each coefficient is a signed 16-bit or 24-bit
sample. Stereo HRTFs interleave left/right ear coefficients. The HRIRs must
be minimum-phase. This allows the use of a smaller filter length, reducing
computation. For reference, the default data set uses a 32-point filter while
even the smallest data set provided by MIT used a 128-sample filter (a 4x
reduction by applying minimum-phase reconstruction). Theoretically, one could
further reduce the minimum-phase version down to a 16-point filter with only a
small reduction in quality.
reduction by applying minimum-phase reconstruction).
After the coefficients is an array of unsigned 8-bit delay values, one for
each HRIR. This is the propagation delay (in samples) a signal must wait before
being convolved with the corresponding minimum-phase HRIR filter.
each HRIR (with stereo HRTFs interleaving left/right ear delays). This is the
propagation delay (in samples) a signal must wait before being convolved with
the corresponding minimum-phase HRIR filter.