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diff --git a/indra/media_plugins/winmmshim/winmm_shim.cpp b/indra/media_plugins/winmmshim/winmm_shim.cpp
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+/**
+ * @file winmmshim.cpp
+ * @brief controls volume level of process by intercepting calls to winmm.dll
+ *
+ * $LicenseInfo:firstyear=2010&license=viewergpl$
+ *
+ * Copyright (c) 2010, Linden Research, Inc.
+ *
+ * Second Life Viewer Source Code
+ * The source code in this file ("Source Code") is provided by Linden Lab
+ * to you under the terms of the GNU General Public License, version 2.0
+ * ("GPL"), unless you have obtained a separate licensing agreement
+ * ("Other License"), formally executed by you and Linden Lab. Terms of
+ * the GPL can be found in doc/GPL-license.txt in this distribution, or
+ * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
+ *
+ * There are special exceptions to the terms and conditions of the GPL as
+ * it is applied to this Source Code. View the full text of the exception
+ * in the file doc/FLOSS-exception.txt in this software distribution, or
+ * online at
+ * http://secondlifegrid.net/programs/open_source/licensing/flossexception
+ *
+ * By copying, modifying or distributing this software, you acknowledge
+ * that you have read and understood your obligations described above,
+ * and agree to abide by those obligations.
+ *
+ * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
+ * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
+ * COMPLETENESS OR PERFORMANCE.
+ * $/LicenseInfo$
+ */
+#include "forwarding_api.h"
+#include <xmmintrin.h>
+#include <map>
+#include <math.h>
+
+using std::wstring;
+
+static float sVolumeLevel = 1.f;
+static bool sMute = false;
+
+BOOL APIENTRY DllMain( HMODULE hModule,
+ DWORD ul_reason_for_call,
+ LPVOID lpReserved
+ )
+{
+ static bool initialized = false;
+ // do this only once
+ if (!initialized)
+ { // bind to original winmm.dll
+ TCHAR system_path[MAX_PATH];
+ TCHAR dll_path[MAX_PATH];
+ ::GetSystemDirectory(system_path, MAX_PATH);
+
+ // grab winmm.dll from system path, where it should live
+ wsprintf(dll_path, "%s\\winmm.dll", system_path);
+ HMODULE winmm_handle = ::LoadLibrary(dll_path);
+
+ if (winmm_handle != NULL)
+ { // we have a dll, let's get out pointers!
+ initialized = true;
+ init_function_pointers(winmm_handle);
+ return true;
+ }
+
+ // failed to initialize real winmm.dll
+ return false;
+ }
+ return true;
+}
+
+
+extern "C"
+{
+ // tracks the requested format for a given waveout buffer
+ struct WaveOutFormat
+ {
+ WaveOutFormat(int bits_per_sample)
+ : mBitsPerSample(bits_per_sample)
+ {}
+ int mBitsPerSample;
+ };
+ typedef std::map<HWAVEOUT, WaveOutFormat*> wave_out_map_t;
+ static wave_out_map_t sWaveOuts;
+
+ MMRESULT WINAPI waveOutOpen( LPHWAVEOUT phwo, UINT uDeviceID, LPCWAVEFORMATEX pwfx, DWORD_PTR dwCallback, DWORD_PTR dwInstance, DWORD fdwOpen)
+ {
+ if (pwfx->wFormatTag != WAVE_FORMAT_PCM
+ || (pwfx->wBitsPerSample != 8 && pwfx->wBitsPerSample != 16))
+ { // uncompressed 8 and 16 bit sound are the only types we support
+ return WAVERR_BADFORMAT;
+ }
+
+ MMRESULT result = waveOutOpen_orig(phwo, uDeviceID, pwfx, dwCallback, dwInstance, fdwOpen);
+ if (result == MMSYSERR_NOERROR
+ && ((fdwOpen & WAVE_FORMAT_QUERY) == 0)) // not just querying for format support
+ { // remember the requested bits per sample, and associate with the given handle
+ WaveOutFormat* wave_outp = new WaveOutFormat(pwfx->wBitsPerSample);
+ sWaveOuts.insert(std::make_pair(*phwo, wave_outp));
+ }
+ return result;
+ }
+
+ MMRESULT WINAPI waveOutClose( HWAVEOUT hwo)
+ {
+ wave_out_map_t::iterator found_it = sWaveOuts.find(hwo);
+ if (found_it != sWaveOuts.end())
+ { // forget what we know about this handle
+ delete found_it->second;
+ sWaveOuts.erase(found_it);
+ }
+ return waveOutClose_orig( hwo);
+ }
+
+ MMRESULT WINAPI waveOutWrite( HWAVEOUT hwo, LPWAVEHDR pwh, UINT cbwh)
+ {
+ MMRESULT result = MMSYSERR_NOERROR;
+
+ if (sMute)
+ { // zero out the audio buffer when muted
+ memset(pwh->lpData, 0, pwh->dwBufferLength);
+ }
+ else
+ {
+ wave_out_map_t::iterator found_it = sWaveOuts.find(hwo);
+ if (found_it != sWaveOuts.end())
+ {
+ WaveOutFormat* formatp = found_it->second;
+ switch (formatp->mBitsPerSample){
+ case 8:
+ {
+ char volume = (char)(sVolumeLevel * 127.f);
+ for (unsigned int i = 0; i < pwh->dwBufferLength; i++)
+ {
+ // unsigned multiply doesn't use most significant bit, so shift by 7 bits
+ // to get resulting value back into 8 bits
+ pwh->lpData[i] = (pwh->lpData[i] * volume) >> 7;
+ }
+ break;
+ }
+ case 16:
+ {
+ short volume_16 = (short)(sVolumeLevel * 32767.f);
+
+ // copy volume level 4 times into 64 bit MMX register
+ __m64 volume_64 = _mm_set_pi16(volume_16, volume_16, volume_16, volume_16);
+ __m64 *sample_64;
+ // for everything that can be addressed in 64 bit multiples...
+ for (sample_64 = (__m64*)pwh->lpData;
+ sample_64 < (__m64*)(pwh->lpData + pwh->dwBufferLength);
+ ++sample_64)
+ {
+ //...multiply the samples by the volume...
+ __m64 scaled_sample = _mm_mulhi_pi16(*sample_64, volume_64);
+ // ...and shift left 1 bit since an unsigned multiple loses the most significant bit
+ // 0x7FFF * 0x7FFF = 0x3fff0001
+ // 0x3fff0001 << 1 = 0x7ffe0002
+ // notice that the LSB is always 0...should consider dithering
+ *sample_64 = _mm_slli_pi16(scaled_sample, 1);
+ }
+
+ // the captain has turned off the MMX sign, you are now free to use floating point registers
+ _mm_empty();
+
+ for (short* sample_16 = (short*)sample_64;
+ sample_16 < (short*)(pwh->lpData + pwh->dwBufferLength);
+ ++sample_16)
+ { // finish remaining samples that didn't fit into 64 bit register
+ *sample_16 = (*sample_16 * volume_16) >> 15;
+ }
+
+ break;
+ }
+ default:
+ // don't do anything
+ break;
+ }
+ }
+ }
+ return waveOutWrite_orig( hwo, pwh, cbwh);
+ }
+
+ void WINAPI setPluginVolume(float volume)
+ {
+ sVolumeLevel = volume;
+ }
+
+ void WINAPI setPluginMute(bool mute)
+ {
+ sMute = mute;
+ }
+}