cras/src/server/softvol_curve.c

/* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include <stddef.h>
#include <stdlib.h>

#include "cras_volume_curve.h"
#include "softvol_curve.h"

/* This is a ramp that increases 0.5dB per step, for a total range of 50dB. */
const float softvol_scalers[101] = {
	0.003162, /* volume 0 */
	0.003350, 0.003548, 0.003758, 0.003981, 0.004217, 0.004467, 0.004732,
	0.005012, 0.005309, 0.005623, 0.005957, 0.006310, 0.006683, 0.007079,
	0.007499, 0.007943, 0.008414, 0.008913, 0.009441, 0.010000, 0.010593,
	0.011220, 0.011885, 0.012589, 0.013335, 0.014125, 0.014962, 0.015849,
	0.016788, 0.017783, 0.018836, 0.019953, 0.021135, 0.022387, 0.023714,
	0.025119, 0.026607, 0.028184, 0.029854, 0.031623, 0.033497, 0.035481,
	0.037584, 0.039811, 0.042170, 0.044668, 0.047315, 0.050119, 0.053088,
	0.056234, 0.059566, 0.063096, 0.066834, 0.070795, 0.074989, 0.079433,
	0.084140, 0.089125, 0.094406, 0.100000, 0.105925, 0.112202, 0.118850,
	0.125893, 0.133352, 0.141254, 0.149624, 0.158489, 0.167880, 0.177828,
	0.188365, 0.199526, 0.211349, 0.223872, 0.237137, 0.251189, 0.266073,
	0.281838, 0.298538, 0.316228, 0.334965, 0.354813, 0.375837, 0.398107,
	0.421697, 0.446684, 0.473151, 0.501187, 0.530884, 0.562341, 0.595662,
	0.630957, 0.668344, 0.707946, 0.749894, 0.794328, 0.841395, 0.891251,
	0.944061, 1.000000, /* volume 100 */
};

float *softvol_build_from_curve(const struct cras_volume_curve *curve)
{
	float *scalers;
	unsigned int volume;

	if (!curve)
		return NULL;

	scalers = (float *)malloc(NUM_VOLUME_STEPS * sizeof(float));
	if (!scalers)
		return NULL;

	/* When software volume is used, it is assumed all volume curve values
	 * are relative to 0 dBFS when converting to scale. If a positive dBFS
	 * value is specified in curve config, it will be treated as invalid
	 * and clip to 1.0 in scale.
	 */
	for (volume = 0; volume <= MAX_VOLUME; volume++) {
		scalers[volume] = convert_softvol_scaler_from_dB(
			curve->get_dBFS(curve, volume));
		if (scalers[volume] > 1.0)
			scalers[volume] = 1.0;
		/* Clip scalers so that all values are non-zero to make volume
		 * ramping simpler. Because of how mix_ops treats small values,
		 * this should be effectively the same as a 0 value. */
		else if (scalers[volume] < 1e-7)
			scalers[volume] = 1e-7;
	}

	return scalers;
}