volume: guarantee dB/linear conversion is reversible

diff --git a/src/pulse/volume.c b/src/pulse/volume.c
index 42cde5b9676bd4d0c313854601bfda277be0c908..c23f360b2e2df651e57c4f8f502d240105998ca9 100644 (file)
--- a/src/pulse/volume.c
+++ b/src/pulse/volume.c
@@ -205,9 +205,12 @@ pa_volume_t pa_sw_volume_from_linear(double v) {
      *
      * http://www.robotplanet.dk/audio/audio_gui_design/
      * http://lists.linuxaudio.org/pipermail/linux-audio-dev/2009-May/thread.html#23151
+     *
+     * We make sure that the conversion to linear and back yields the
+     * same volume value! That's why we need the lround() below!
      */
 
-    return (pa_volume_t) (cbrt(v) * PA_VOLUME_NORM);
+    return (pa_volume_t) lround(cbrt(v) * PA_VOLUME_NORM);
 }
 
 double pa_sw_volume_to_linear(pa_volume_t v) {

diff --git a/src/tests/voltest.c b/src/tests/voltest.c
index 2dcfa53cdce2367ba782fa06c4ce6e8a10d5706a..64aec5c6ba957affc6b123349291320aa64421c4 100644 (file)
--- a/src/tests/voltest.c
+++ b/src/tests/voltest.c
@@ -1,8 +1,33 @@
+/***
+  This file is part of PulseAudio.
+
+  PulseAudio is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as published
+  by the Free Software Foundation; either version 2.1 of the License,
+  or (at your option) any later version.
+
+  PulseAudio is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with PulseAudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
 #include <stdio.h>
 
 #include <pulse/volume.h>
 #include <pulse/gccmacro.h>
 
+#include <pulsecore/macro.h>
+
 int main(int argc, char *argv[]) {
     pa_volume_t v;
     pa_cvolume cv;
@@ -60,5 +85,16 @@ int main(int argc, char *argv[]) {
                 printf("After: volume: [%s]; balance: %2.1f (intended: %2.1f) %s\n", pa_cvolume_snprint(s, sizeof(s), &r), k, b, k < b-.05 || k > b+.5 ? "MISMATCH" : "");
             }
 
+    for (v = PA_VOLUME_MUTED; v <= PA_VOLUME_NORM*2; v += 1) {
+
+        double l = pa_sw_volume_to_linear(v);
+        pa_volume_t k = pa_sw_volume_from_linear(l);
+        double db = pa_sw_volume_to_dB(v);
+        pa_volume_t r = pa_sw_volume_from_dB(db);
+
+        pa_assert(k == v);
+        pa_assert(r == v);
+    }
+
     return 0;
 }