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