--- mozilla/media/libcubeb/src/cubeb_sndio.c.orig	2018-05-16 23:58:58.000000000 +0200

+++ mozilla/media/libcubeb/src/cubeb_sndio.c

@@ -43,17 +43,33 @@ struct cubeb_stream {

   cubeb_data_callback data_cb;    /* cb to preapare data */

   cubeb_state_callback state_cb;  /* cb to notify about state changes */

   void *arg;			  /* user arg to {data,state}_cb */

+  float volume;                   /* current volume */

 };

 static void

-float_to_s16(void *ptr, long nsamp)

+s16_setvol(void *ptr, long nsamp, float volume)

 {

   int16_t *dst = ptr;

+  int32_t mult = volume * 32768;

+  int32_t s;

+

+  while (nsamp-- > 0) {

+    s = *dst;

+    s = (s * mult) >> 15;

+    *(dst++) = s;

+  }

+}

+

+static void

+float_to_s16(void *ptr, long nsamp, float volume)

+{

+  int16_t *dst = ptr;

   float *src = ptr;

+  float mult = volume * 32768;

   int s;

   while (nsamp-- > 0) {

-    s = lrintf(*(src++) * 32768);

+    s = lrintf(*(src++) * mult);

     if (s < -32768)

       s = -32768;

     else if (s > 32767)

@@ -111,7 +127,9 @@ sndio_mainloop(void *arg)

         break;

       }

       if (s->conv)

-        float_to_s16(s->buf, nfr * s->pchan);

+        float_to_s16(s->buf, nfr * s->pchan, s->volume);

+      else

+        s16_setvol(s->buf, nfr * s->pchan, s->volume);

       start = 0;

       end = nfr * s->bpf;

     }

@@ -260,6 +278,7 @@ sndio_stream_init(cubeb * context,

     free(s);

     return CUBEB_ERROR;

   }

+  s->volume = 1.;

   *stream = s;

   DPR("sndio_stream_init() end, ok\n");

   (void)context;

@@ -346,7 +365,11 @@ sndio_stream_set_volume(cubeb_stream *s, float volume)

 {

   DPR("sndio_stream_set_volume(%f)\n", volume);

   pthread_mutex_lock(&s->mtx);

-  sio_setvol(s->hdl, SIO_MAXVOL * volume);

+  if (volume < 0.) 

+    volume = 0.; 

+  else if (volume > 1.0) 

+    volume = 1.; 

+  s->volume = volume; 

   pthread_mutex_unlock(&s->mtx);

   return CUBEB_OK;

 }