Date: Tue, 13 Apr 2004 14:17:06 +0300 (EEST) From: Andriy Gapon <avg@icyb.net.ua> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/65485: sb16 mixer: uneven mapping from % volume to absolute volume Message-ID: <200404131117.i3DBH61j048928@oddity.topspin.kiev.ua> Resent-Message-ID: <200404131150.i3DBoElq021517@freefall.freebsd.org>
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>Number: 65485 >Category: kern >Synopsis: sb16 mixer: uneven mapping from % volume to absolute volume >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Tue Apr 13 04:50:13 PDT 2004 >Closed-Date: >Last-Modified: >Originator: Andriy Gapon >Release: FreeBSD 5.2.1-RELEASE-p4 i386 >Organization: >Environment: System: FreeBSD x.x.x.x 5.2.1-RELEASE-p4 FreeBSD 5.2.1-RELEASE-p4 #16: Fri Apr 2 20:05:58 EEST 2004 avg i386 any i386 FreeBSD 4.x, 5.x with SB16 >Description: current function for mapping userland relative volume levels (0-100) to device volume levels looks like this: left = (left * max) / 100; this is probably good enough for main or pcm volume where max=31, but is suboptimal for ogain, where max=3, because 0-100 range is virtually split into only 3 subranges instead of possible 4: 00-33 => 0 34-66 => 1 67-99 => 2 100 => 3 IMHO, something like the following fomula should do better: abs = [(max+1)*rel/max]*max/100 [] stands fo integer part >How-To-Repeat: try to regulate ogain and you will see /hear :-)/ that 0-100 range is actually split into 3 subranges and maximum is reached only when volume==100% >Fix: --- sb16.c.patch begins here --- --- sb16.c.orig Tue Apr 13 14:09:46 2004 +++ sb16.c Tue Apr 13 14:10:03 2004 @@ -326,6 +326,12 @@ } static int +rel2abs_volume(int x, int max) +{ + return ((((max + 1) * x) / max) * max) / 100; +} + +static int sb16mix_set(struct snd_mixer *m, unsigned dev, unsigned left, unsigned right) { struct sb_info *sb = mix_getdevinfo(m); @@ -335,8 +341,8 @@ e = &sb16_mixtab[dev]; max = (1 << e->bits) - 1; - left = (left * max) / 100; - right = (right * max) / 100; + left = rel2abs_volume(left, max); + right = rel2abs_volume(right, max); sb_setmixer(sb, e->reg, left << e->ofs); if (e->stereo) --- sb16.c.patch ends here --- >Release-Note: >Audit-Trail: >Unformatted:
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