Add config options for the sound buffer cache size

The cache size is specified with a min/max range, intended to avoid constant
unloading once the limit is reached. This way, buffers can be unloaded down to
a reasonable mimimum, allowing some more buffers to be subsequently loaded
without causing more unloading.

apps/openmw/mwsound/soundmanagerimp.cpp

@@ -66,6 +66,11 @@ namespace MWSound
         mFootstepsVolume = Settings::Manager::getFloat("footsteps volume", "Sound");
         mFootstepsVolume = std::min(std::max(mFootstepsVolume, 0.0f), 1.0f);
 
+        mBufferCacheMin = std::max(Settings::Manager::getInt("buffer cache min", "Sound"), 1);
+        mBufferCacheMax = std::max(Settings::Manager::getInt("buffer cache max", "Sound"), 1);
+        mBufferCacheMax *= 1024*1024;
+        mBufferCacheMin = std::min(mBufferCacheMin*1024*1024, mBufferCacheMax);
+
         std::cout << "Sound output: " << SOUND_OUT << std::endl;
         std::cout << "Sound decoder: " << SOUND_IN << std::endl;
 
@@ -184,9 +189,9 @@ namespace MWSound
             sfx->mHandle = mOutput->loadSound(sfx->mResourceName);
             mBufferCacheSize += mOutput->getSoundDataSize(sfx->mHandle);
 
-            // NOTE: Max sound buffer cache size is 15MB. Make configurable?
-            while(mBufferCacheSize > 15*1024*1024)
+            if(mBufferCacheSize > mBufferCacheMax)
             {
+                do {
                     if(mUnusedBuffers.empty())
                     {
                         std::cerr<< "No unused sound buffers to free, using "<<mBufferCacheSize<<" bytes!" <<std::endl;
@@ -199,6 +204,7 @@ namespace MWSound
                     unused->mHandle = 0;
 
                     mUnusedBuffers.pop_back();
+                } while(mBufferCacheSize > mBufferCacheMin);
             }
             mUnusedBuffers.push_front(sfx);
         }

apps/openmw/mwsound/soundmanagerimp.hpp

@@ -56,6 +56,8 @@ namespace MWSound
         // back, allowing existing Sound_Buffer references/pointers to remain
         // valid.
         SoundBufferList mSoundBuffers;
+        size_t mBufferCacheMin;
+        size_t mBufferCacheMax;
         size_t mBufferCacheSize;
 
         typedef std::map<std::string,Sound_Buffer*> NameBufferMap;

files/settings-default.cfg

@@ -165,6 +165,15 @@ sfx volume = 1.0
 # Voice dialog volume.
 voice volume = 0.8
 
+# Minimum size to use for the sound buffer cache, in MB. When the cache is
+# filled, old buffers will be unloaded until it's using no more than this much
+# memory. Must be less than or equal to 'buffer cache max'.
+buffer cache min = 14
+
+# Maximum size to use for the sound buffer cache, in MB. The cache can use up
+# to this much memory until old buffers get purged.
+buffer cache max = 16
+
 [Video]
 
 # Resolution of the OpenMW window or screen.