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Add helpers for converting to/from normalized (perceptual) volume

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These routines were taken from alsamixer and converted to fixed
point for Rockbox.

Change-Id: I64e8bf08da02b1e6e3ef10fdc78254bf8e87ff20
This commit is contained in:
Aidan MacDonald 2022-11-22 19:19:01 +00:00
parent 66519000f4
commit dc83963962
3 changed files with 132 additions and 0 deletions
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8
apps/misc.h
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@ -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 */