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audioconvert: avoid float calculations when mixing integer-formatted channels

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The patch calculates a second channel mixing matrix from the current one. The
matrix contains the original values * (2^10) as integers. This matrix is used
when integer-formatted channels are mixed.

On a ARM Cortex-A8, single core, 800MHz this improves performance in a
testcase from 29s to 9s for downmixing 6 channels to stereo.

https://bugzilla.gnome.org/show_bug.cgi?id=747005
This commit is contained in:
Bernhard Miller 2015-03-30 11:24:46 +02:00 committed by Sebastian Dröge
parent 84638199e7
commit b2db18cda2
2 changed files with 40 additions and 1 deletions
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5
gst/audioconvert/audioconvert.h
View file

@ -107,6 +107,11 @@ struct _AudioConvertCtx
/* channel conversion matrix, m[in_channels][out_channels].
* If identity matrix, passthrough applies. */
gfloat **matrix;
/* channel conversion matrix with int values, m[in_channels][out_channels].
* this is matrix * (2^10) as integers */
gint **matrix_int;
/* temp storage for channelmix */
gpointer tmp;

36
gst/audioconvert/gstchannelmix.c
View file

@ -29,6 +29,8 @@
#include "gstchannelmix.h"
#define INT_MATRIX_FACTOR_EXPONENT 10
/*
* Channel matrix functions.
*/
@ -48,6 +50,13 @@ gst_channel_mix_unset_matrix (AudioConvertCtx * this)
g_free (this->matrix);
this->matrix = NULL;
for (i = 0; i < this->in.channels; i++)
g_free (this->matrix_int[i]);
g_free (this->matrix_int);
this->matrix_int = NULL;
g_free (this->tmp);
this->tmp = NULL;
}
@ -590,6 +599,26 @@ gst_channel_mix_fill_matrix (AudioConvertCtx * this)
}
}
/* only call this after this->matrix is fully set up and normalized */
static void
gst_channel_mix_setup_matrix_int (AudioConvertCtx * this)
{
gint i, j;
gfloat tmp;
gfloat factor = (1 << INT_MATRIX_FACTOR_EXPONENT);
this->matrix_int = g_new0 (gint32 *, this->in.channels);
for (i = 0; i < this->in.channels; i++) {
this->matrix_int[i] = g_new (gint32, this->out.channels);
for (j = 0; j < this->out.channels; j++) {
tmp = this->matrix[i][j] * factor;
this->matrix_int[i][j] = (gint)tmp;
}
}
}
/* only call after this->out and this->in are filled in */
void
gst_channel_mix_setup_matrix (AudioConvertCtx * this)
@ -618,6 +647,8 @@ gst_channel_mix_setup_matrix (AudioConvertCtx * this)
/* setup the matrix' internal values */
gst_channel_mix_fill_matrix (this);
gst_channel_mix_setup_matrix_int(this);
#ifndef GST_DISABLE_GST_DEBUG
/* debug */
{
@ -694,9 +725,12 @@ gst_channel_mix_mix_int (AudioConvertCtx * this,
/* convert */
res = 0;
for (in = 0; in < inchannels; in++) {
res += in_data[n * inchannels + in] * this->matrix[in][out];
res += in_data[n * inchannels + in] * (gint64)this->matrix_int[in][out];
}
/* remove factor from int matrix */
res = res >> INT_MATRIX_FACTOR_EXPONENT;
/* clip (shouldn't we use doubles instead as intermediate format?) */
if (res < G_MININT32)
res = G_MININT32;