cras/src/server/cras_ramp.c

/* Copyright 2016 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 <syslog.h>

#include "cras_ramp.h"


/*
 * State of cras_ramp:
 *   CRAS_RAMP_STATE_IDLE: No ramping is started, or a ramping is already done.
 *   CRAS_RAMP_STATE_UP: Ramping up from 0 to 1.
 *   CRAS_RAMP_STATE_DOWN: Ramping down from certain scaler to 0.
 */
enum CRAS_RAMP_STATE {
	CRAS_RAMP_STATE_IDLE,
	CRAS_RAMP_STATE_UP,
	CRAS_RAMP_STATE_DOWN,
};

/*
 * Struct to hold ramping information.
 * Members:
 *   state: Current state. One of CRAS_RAMP_STATE.
 *   ramped_frames: Number of frames that have passed after starting ramping.
 *   duration_frames: The targeted number of frames for whole ramping duration.
 *   increment: The scaler increment that should be added to scaler for
 *              every frame.
 *   start_scaler: The initial scaler.
 *   cb: Callback function to call after ramping is done.
 *   cb_data: Data passed to cb.
 */
struct cras_ramp {
	enum CRAS_RAMP_STATE state;
	int ramped_frames;
	int duration_frames;
	float increment;
	float start_scaler;
	void (*cb)(void *data);
	void *cb_data;
};

void cras_ramp_destroy(struct cras_ramp* ramp)
{
	free(ramp);
}

struct cras_ramp* cras_ramp_create()
{
	struct cras_ramp* ramp;
	ramp = (struct cras_ramp*)malloc(sizeof(*ramp));
	if (ramp == NULL) {
		return NULL;
	}
	cras_ramp_reset(ramp);
	return ramp;
}

int cras_ramp_reset(struct cras_ramp *ramp) {
	ramp->state = CRAS_RAMP_STATE_IDLE;
	ramp->ramped_frames = 0;
	ramp->duration_frames = 0;
	ramp->increment = 0;
	ramp->start_scaler = 1.0;
	return 0;
}

int cras_ramp_start(struct cras_ramp *ramp, int is_up, int duration_frames,
		    cras_ramp_cb cb, void *cb_data)
{
	struct cras_ramp_action action;

	/* Get current scaler position so it can serve as new start scaler. */
	action = cras_ramp_get_current_action(ramp);
	if (action.type == CRAS_RAMP_ACTION_INVALID)
		return -EINVAL;

        /* Set initial scaler to current scaler so ramping up/down can be
         * smoothly switched. */
	if (is_up) {
		ramp->state = CRAS_RAMP_STATE_UP;
		if (action.type == CRAS_RAMP_ACTION_NONE)
			ramp->start_scaler = 0;
		else
			ramp->start_scaler = action.scaler;
		ramp->increment = (1 - ramp->start_scaler) / duration_frames;
	} else {
		ramp->state = CRAS_RAMP_STATE_DOWN;
		if (action.type == CRAS_RAMP_ACTION_NONE)
			ramp->start_scaler = 1;
		else
			ramp->start_scaler = action.scaler;

		ramp->increment = -ramp->start_scaler / duration_frames;
	}
	ramp->ramped_frames = 0;
	ramp->duration_frames = duration_frames;
	ramp->cb = cb;
	ramp->cb_data = cb_data;
	return 0;
}

struct cras_ramp_action cras_ramp_get_current_action(const struct cras_ramp *ramp)
{
	struct cras_ramp_action action;

	if (ramp->ramped_frames < 0) {
		action.type = CRAS_RAMP_ACTION_INVALID;
		action.scaler = 1.0;
		action.increment = 0.0;
		return action;
	}

	switch (ramp->state) {
	case CRAS_RAMP_STATE_IDLE:
		action.type = CRAS_RAMP_ACTION_NONE;
		action.scaler = 1.0;
		action.increment = 0.0;
		break;
	case CRAS_RAMP_STATE_DOWN:
		action.type = CRAS_RAMP_ACTION_PARTIAL;
		action.scaler = ramp->start_scaler +
				ramp->ramped_frames * ramp->increment;
		action.increment = ramp->increment;
		break;
	case CRAS_RAMP_STATE_UP:
		action.type = CRAS_RAMP_ACTION_PARTIAL;
		action.scaler = ramp->start_scaler +
				ramp->ramped_frames * ramp->increment;
		action.increment = ramp->increment;
		break;
	}
	return action;
}

int cras_ramp_update_ramped_frames(
		struct cras_ramp *ramp, int num_frames)
{
	if (ramp->state == CRAS_RAMP_STATE_IDLE)
		return -EINVAL;
	ramp->ramped_frames += num_frames;
	if (ramp->ramped_frames >= ramp->duration_frames) {
		ramp->state = CRAS_RAMP_STATE_IDLE;
		if (ramp->cb)
			ramp->cb(ramp->cb_data);
	}
	return 0;
}