From 739a4b3d2318f05eb7101c2baa861e5c636125a5 Mon Sep 17 00:00:00 2001 From: Ian Ray Date: Wed, 30 Aug 2017 11:09:48 +0300 Subject: [PATCH 15/48] alsa-mixer: round, not truncate, in to_alsa_dB to_alsa_dB() returns a result rounded to two decimal places (instead of using integer truncation) to avoid small errors when converting between dB and volume. Consider playback at -22 dB (which is supported by ALSA) but results in the higher level of -21 dB plus software attenuation. pa_sw_volume_from_dB(-22) = 28172 pa_sw_volume_to_dB(28172) = -21.9997351 to_alsa_dB(-21.9997351) = -2199 ALSA value 106 = -2200 ALSA value 107 = -2100 ... rounding = +1 /* "accurate or first above" */ snd_mixer_selem_ask_playback_dB_vol(me, -2199, rounding, &alsa_val) alsa_val = -2100 Signed-off-by: Ian Ray --- src/modules/alsa/alsa-mixer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c index f59cad39..aeaf12c4 100644 --- a/src/modules/alsa/alsa-mixer.c +++ b/src/modules/alsa/alsa-mixer.c @@ -700,7 +700,7 @@ void pa_alsa_path_set_free(pa_alsa_path_set *ps) { } static long to_alsa_dB(pa_volume_t v) { - return (long) (pa_sw_volume_to_dB(v) * 100.0); + return lround(pa_sw_volume_to_dB(v) * 100.0); } static pa_volume_t from_alsa_dB(long v) { -- 2.13.6