From f63d8dbf38352b9ca0f1dc5e8eab87242c81b3ee Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Sun, 29 Nov 2009 23:02:21 -0800
Subject: [PATCH] Enable real-time priority for ALSA, OSS, and DirectSound
 mixing loops

---
 Alc/alsa.c                | 16 ++++++++++++----
 Alc/dsound.c              |  5 +++--
 Alc/oss.c                 |  4 ++++
 OpenAL32/Include/alMain.h | 16 ++++++++++++++++
 4 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/Alc/alsa.c b/Alc/alsa.c
index 76f12fdb..cfe80640 100644
--- a/Alc/alsa.c
+++ b/Alc/alsa.c
@@ -271,6 +271,8 @@ static ALuint ALSAProc(ALvoid *ptr)
     char *WritePtr;
     int err;
 
+    EnableRTPrio();
+
     while(!data->killNow)
     {
         int state = verify_state(data->pcmHandle);
@@ -343,6 +345,8 @@ static ALuint ALSANoMMapProc(ALvoid *ptr)
     snd_pcm_sframes_t avail;
     char *WritePtr;
 
+    EnableRTPrio();
+
     while(!data->killNow)
     {
         int state = verify_state(data->pcmHandle);
@@ -396,6 +400,8 @@ static ALuint ALSANoMMapCaptureProc(ALvoid *ptr)
     alsa_data *data = (alsa_data*)pDevice->ExtraData;
     snd_pcm_sframes_t avail;
 
+    EnableRTPrio();
+
     while(!data->killNow)
     {
         int state = verify_state(data->pcmHandle);
@@ -669,6 +675,9 @@ static ALCboolean alsa_reset_playback(ALCdevice *device)
             AL_PRINT("buffer malloc failed\n");
             return ALC_FALSE;
         }
+        device->UpdateSize = periodSizeInFrames;
+        device->NumUpdates = periods;
+        device->Frequency = rate;
         data->thread = StartThread(ALSANoMMapProc, device);
     }
     else
@@ -679,6 +688,9 @@ static ALCboolean alsa_reset_playback(ALCdevice *device)
             AL_PRINT("prepare error: %s\n", psnd_strerror(i));
             return ALC_FALSE;
         }
+        device->UpdateSize = periodSizeInFrames;
+        device->NumUpdates = periods;
+        device->Frequency = rate;
         data->thread = StartThread(ALSAProc, device);
     }
     if(data->thread == NULL)
@@ -689,10 +701,6 @@ static ALCboolean alsa_reset_playback(ALCdevice *device)
         return ALC_FALSE;
     }
 
-    device->UpdateSize = periodSizeInFrames;
-    device->NumUpdates = periods;
-    device->Frequency = rate;
-
     return ALC_TRUE;
 }
 
diff --git a/Alc/dsound.c b/Alc/dsound.c
index 374cb00c..8d7b42b9 100644
--- a/Alc/dsound.c
+++ b/Alc/dsound.c
@@ -134,6 +134,8 @@ static ALuint DSoundProc(ALvoid *ptr)
     DWORD avail;
     HRESULT err;
 
+    EnableRTPrio();
+
     memset(&DSBCaps, 0, sizeof(DSBCaps));
     DSBCaps.dwSize = sizeof(DSBCaps);
     err = IDirectSoundBuffer_GetCaps(pData->DSsbuffer, &DSBCaps);
@@ -413,6 +415,7 @@ static ALCboolean DSoundResetPlayback(ALCdevice *device)
     if(SUCCEEDED(hr))
     {
         device->ExtraData = pData;
+        device->Format = format;
         pData->thread = StartThread(DSoundProc, device);
         if(!pData->thread)
             hr = E_FAIL;
@@ -429,8 +432,6 @@ static ALCboolean DSoundResetPlayback(ALCdevice *device)
         return ALC_FALSE;
     }
 
-    device->Format = format;
-
     return ALC_TRUE;
 }
 
diff --git a/Alc/oss.c b/Alc/oss.c
index c3cd9528..4a7a48be 100644
--- a/Alc/oss.c
+++ b/Alc/oss.c
@@ -82,6 +82,8 @@ static ALuint OSSProc(ALvoid *ptr)
     ALint frameSize;
     ssize_t wrote;
 
+    EnableRTPrio();
+
     frameSize = aluChannelsFromFormat(pDevice->Format) *
                 aluBytesFromFormat(pDevice->Format);
 
@@ -122,6 +124,8 @@ static ALuint OSSCaptureProc(ALvoid *ptr)
     int frameSize;
     int amt;
 
+    EnableRTPrio();
+
     frameSize  = aluBytesFromFormat(pDevice->Format);
     frameSize *= aluChannelsFromFormat(pDevice->Format);
 
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index e235794a..0820b9dc 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -181,6 +181,22 @@ static __inline ALuint NextPowerOf2(ALuint value)
     return powerOf2;
 }
 
+static __inline void EnableRTPrio()
+{
+#ifdef _WIN32
+    SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);
+#elif defined(HAVE_PTHREAD_SETSCHEDPARAM)
+    struct sched_param param;
+
+    /* Use the minimum real-time priority possible for now (on Linux this
+     * should be 1 for SCHED_RR) */
+    param.sched_priority = sched_get_priority_min(SCHED_RR);
+    pthread_setschedparam(pthread_self(), SCHED_RR, &param);
+#else
+    /* Real-time priority not available */
+#endif
+}
+
 
 typedef struct {
     ALCboolean (*OpenPlayback)(ALCdevice*, const ALCchar*);
-- 
2.11.4.GIT