From dc839639620352c5fa9b63db6679126ec5bcfba8 Mon Sep 17 00:00:00 2001 From: Aidan MacDonald Date: Tue, 22 Nov 2022 19:19:01 +0000 Subject: Add helpers for converting to/from normalized (perceptual) volume These routines were taken from alsamixer and converted to fixed point for Rockbox. Change-Id: I64e8bf08da02b1e6e3ef10fdc78254bf8e87ff20 --- apps/misc.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ apps/misc.h | 8 +++++ 2 files changed, 110 insertions(+) (limited to 'apps') diff --git a/apps/misc.c b/apps/misc.c index e17df02bff..d4c7108d28 100644 --- a/apps/misc.c +++ b/apps/misc.c @@ -1664,3 +1664,105 @@ int core_load_bmp(const char * filename, struct bitmap *bm, const int bmformat, return handle; } #endif /* ndef __PCTOOL__ */ + +/* + * Normalized volume routines adapted from alsamixer volume_mapping.c + */ +/* + * Copyright (c) 2010 Clemens Ladisch + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ +/* + * "The mapping is designed so that the position in the interval is proportional + * to the volume as a human ear would perceive it (i.e., the position is the + * cubic root of the linear sample multiplication factor). For controls with + * a small range (24 dB or less), the mapping is linear in the dB values so + * that each step has the same size visually. Only for controls without dB + * information, a linear mapping of the hardware volume register values is used + * (this is the same algorithm as used in the old alsamixer)." + */ + +#define NVOL_FRACBITS 16 +#define NVOL_UNITY (1L << NVOL_FRACBITS) +#define NVOL_FACTOR (600L << NVOL_FRACBITS) + +#define NVOL_MAX_LINEAR_DB_SCALE (240L << NVOL_FRACBITS) + +#define nvol_div(x,y) fp_div((x), (y), NVOL_FRACBITS) +#define nvol_mul(x,y) fp_mul((x), (y), NVOL_FRACBITS) +#define nvol_exp10(x) fp_exp10((x), NVOL_FRACBITS) +#define nvol_log10(x) fp_log10((x), NVOL_FRACBITS) + +static bool use_linear_dB_scale(long min_vol, long max_vol) +{ + /* + * Alsamixer uses a linear scale for small ranges. + * Commented out so perceptual volume works as advertised on all targets. + */ + /* + return max_vol - min_vol <= NVOL_MAX_LINEAR_DB_SCALE; + */ + + (void)min_vol; + (void)max_vol; + return false; +} + +long to_normalized_volume(long vol, long min_vol, long max_vol, long max_norm) +{ + long norm, min_norm; + + vol <<= NVOL_FRACBITS; + min_vol <<= NVOL_FRACBITS; + max_vol <<= NVOL_FRACBITS; + max_norm <<= NVOL_FRACBITS; + + if (use_linear_dB_scale(min_vol, max_vol)) + { + norm = nvol_div(vol - min_vol, max_vol - min_vol); + } + else + { + min_norm = nvol_exp10(nvol_div(min_vol - max_vol, NVOL_FACTOR)); + norm = nvol_exp10(nvol_div(vol - max_vol, NVOL_FACTOR)); + norm = nvol_div(norm - min_norm, NVOL_UNITY - min_norm); + } + + return nvol_mul(norm, max_norm) >> NVOL_FRACBITS; +} + +long from_normalized_volume(long norm, long min_vol, long max_vol, long max_norm) +{ + long vol, min_norm; + + norm <<= NVOL_FRACBITS; + min_vol <<= NVOL_FRACBITS; + max_vol <<= NVOL_FRACBITS; + max_norm <<= NVOL_FRACBITS; + + vol = nvol_div(norm, max_norm); + + if (use_linear_dB_scale(min_vol, max_vol)) + { + vol = nvol_mul(vol, max_vol - min_vol) + min_vol; + } + else + { + min_norm = nvol_exp10(nvol_div(min_vol - max_vol, NVOL_FACTOR)); + vol = nvol_mul(vol, NVOL_UNITY - min_norm) + min_norm; + vol = nvol_mul(nvol_log10(vol), NVOL_FACTOR) + max_vol; + } + + return vol >> NVOL_FRACBITS; +} diff --git a/apps/misc.h b/apps/misc.h index 403a8c53ac..72b8735c8a 100644 --- a/apps/misc.h +++ b/apps/misc.h @@ -238,4 +238,12 @@ int core_load_bmp(const char *filename, struct bitmap *bm, const int bmformat, ssize_t *buf_reqd, struct buflib_callbacks *ops); #endif +/* Convert a volume (in tenth dB) in the range [min_vol, max_vol] + * to a normalized linear value in the range [0, max_norm]. */ +long to_normalized_volume(long vol, long min_vol, long max_vol, long max_norm); + +/* Inverse of to_normalized_volume(), returns the volume in tenth dB + * for the given normalized volume. */ +long from_normalized_volume(long norm, long min_vol, long max_vol, long max_norm); + #endif /* MISC_H */ -- cgit v1.2.3