Add a method to get the sound stream delay

This helps avoid a lock during the movie player's read method, since it needs
to sync with the current playback position which would otherwise need to get
the movie decoder's current position.

apps/openmw/mwsound/movieaudiofactory.cpp

@@ -60,7 +60,8 @@ namespace MWSound
 
         virtual double getAudioClock()
         {
-            return mAudioTrack->getTimeOffset();
+            return (double)getSampleOffset()/(double)mAVStream->codec->sample_rate -
+                   mAudioTrack->getStreamDelay();
         }
 
         virtual void adjustAudioSettings(AVSampleFormat& sampleFormat, uint64_t& channelLayout, int& sampleRate)

apps/openmw/mwsound/openal_output.cpp

@@ -188,6 +188,7 @@ public:
     virtual void stop();
     virtual bool isPlaying();
     virtual double getTimeOffset();
+    virtual double getStreamDelay() const;
     virtual void applyUpdates();
 
     void play();
@@ -395,6 +396,26 @@ double OpenAL_SoundStream::getTimeOffset()
     return t;
 }
 
+double OpenAL_SoundStream::getStreamDelay() const
+{
+    ALint state = AL_STOPPED;
+    double d = 0.0;
+    ALint offset;
+
+    alGetSourcei(mSource, AL_SAMPLE_OFFSET, &offset);
+    alGetSourcei(mSource, AL_SOURCE_STATE, &state);
+    if(state == AL_PLAYING || state == AL_PAUSED)
+    {
+        ALint queued;
+        alGetSourcei(mSource, AL_BUFFERS_QUEUED, &queued);
+        ALint inqueue = mBufferSize/mFrameSize*queued - offset;
+        d = (double)inqueue / (double)mSampleRate;
+    }
+
+    throwALerror();
+    return d;
+}
+
 void OpenAL_SoundStream::updateAll(bool local)
 {
     alSourcef(mSource, AL_REFERENCE_DISTANCE, mMinDistance);

apps/openmw/mwsound/sound.hpp

@@ -25,6 +25,7 @@ namespace MWSound
         virtual void stop() = 0;
         virtual bool isPlaying() = 0;
         virtual double getTimeOffset() = 0;
+        virtual double getStreamDelay() const { return 0.0; }
         virtual void applyUpdates() = 0;
         void setPosition(const osg::Vec3f &pos) { mPos = pos; }
         void setVolume(float volume) { mVolume = volume; }