Merged r2906:2907 from 1.2 branch to trunk: power of two channels in dsp backend.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%402230

src/audio/dsp/SDL_dspaudio.c

@@ -166,6 +166,15 @@ DSP_OpenDevice(_THIS, const char *devname, int iscapture)
         devname = ((iscapture) ? inputDevices[0] : outputDevices[0]);
     }
 
+    /* Make sure fragment size stays a power of 2, or OSS fails. */
+    /* I don't know which of these are actually legal values, though... */
+    if (this->spec.channels > 8)
+        this->spec.channels = 8;
+    else if (this->spec.channels > 4)
+        this->spec.channels = 4;
+    else if (this->spec.channels > 2)
+        this->spec.channels = 2;
+
     /* Initialize all variables that we clean on shutdown */
     this->hidden = (struct SDL_PrivateAudioData *)
         SDL_malloc((sizeof *this->hidden));