Add Look Ahead to Audio Filter

Util/Audio/OfflineAudioMixer.cs

@@ -98,6 +98,7 @@ namespace ADOFAIRenderer.Util.Audio
 
         // Clip Cache
         private readonly AudioClipCache _clipCache = new();
+        private bool _isPrimed;
 
         public OfflineAudioMixer(int targetChannels, int targetSampleRate)
         {
@@ -113,6 +114,16 @@ namespace ADOFAIRenderer.Util.Audio
             rmsCompressor.Initialize(_targetSampleRate, _targetChannels);
             _filters.AddLast(rmsCompressor);
             
+            var limiter = new RMSCompressor
+            {
+                ThresholdDb = 0, Ratio = float.PositiveInfinity,
+                AttackTime = 0f, ReleaseTime = 0.05f,
+                KneeDb = 10, RmsWindowTime = 0.02f,
+                LookAheadTime = 0.01f
+            };
+            limiter.Initialize(_targetSampleRate, _targetChannels);
+            _filters.AddLast(limiter);
+            
             var hardClip = new HardClip();
             hardClip.Initialize(_targetSampleRate, _targetChannels);
             _filters.AddLast(hardClip);
@@ -173,11 +184,10 @@ namespace ADOFAIRenderer.Util.Audio
                     Pitch = pitch
                 };
                 _activeEvents.Add(ev);
-                if (source != null)
-                {
-                    _sourceMappings.Remove(source);
-                    _sourceMappings.Add(source, ev);
-                }
+                
+                if (!source) return;
+                _sourceMappings.Remove(source);
+                _sourceMappings.Add(source, ev);
             }
         }
 
@@ -216,6 +226,38 @@ namespace ADOFAIRenderer.Util.Audio
                 _bgmSamples = null;
                 _bgmDuration = 0;
                 _clipCache.Clear();
+                _isPrimed = false;
+                foreach (var filter in _filters)
+                {
+                    filter.Reset();
+                }
+            }
+        }
+
+        private void PrimeFilters(double totalLatency, double dspTimeBase)
+        {
+            int latencySamples = (int)Math.Round(totalLatency * _targetSampleRate);
+            if (latencySamples <= 0) return;
+
+            // Rent temporary buffer to prime filters with initial audio
+            float[] tempBuffer = System.Buffers.ArrayPool<float>.Shared.Rent(latencySamples * _targetChannels);
+            try
+            {
+                Array.Clear(tempBuffer, 0, latencySamples * _targetChannels);
+
+                // Mix starting from -totalLatency to 0
+                MixBGM(tempBuffer, latencySamples, -totalLatency, dspTimeBase, totalLatency);
+                MixEffectSounds(tempBuffer, latencySamples, -totalLatency, totalLatency);
+
+                // Feed the buffer into filters to prime circular delay buffers
+                foreach (var filter in _filters)
+                {
+                    filter.ProcessBlock(tempBuffer.AsSpan(0, latencySamples * _targetChannels));
+                }
+            }
+            finally
+            {
+                System.Buffers.ArrayPool<float>.Shared.Return(tempBuffer);
             }
         }
 
@@ -226,11 +268,24 @@ namespace ADOFAIRenderer.Util.Audio
 
             lock (_lock)
             {
+                double totalLatency = 0;
+                foreach (var filter in _filters)
+                {
+                    totalLatency += filter.Latency;
+                }
+
+                // Prime filters on first frame execution if latency exists
+                if (!_isPrimed && totalLatency > 0)
+                {
+                    PrimeFilters(totalLatency, dspTimeBase);
+                    _isPrimed = true;
+                }
+
                 // 1. Mix BGM
-                MixBGM(mixedBuffer, samplesNeeded, frameStartTime, dspTimeBase);
+                MixBGM(mixedBuffer, samplesNeeded, frameStartTime, dspTimeBase, totalLatency);
 
                 // 2. Mix Hitsounds/Effect Sounds
-                MixEffectSounds(mixedBuffer, samplesNeeded, frameStartTime);
+                MixEffectSounds(mixedBuffer, samplesNeeded, frameStartTime, totalLatency);
 
                 foreach (var filter in _filters)
                     filter.ProcessBlock(mixedBuffer.AsSpan(0, samplesNeeded * _targetChannels));
@@ -242,7 +297,7 @@ namespace ADOFAIRenderer.Util.Audio
             }
         }
 
-        private void MixBGM(float[] mixedBuffer, int samplesNeeded, double frameStartTime, double dspTimeBase)
+        private void MixBGM(float[] mixedBuffer, int samplesNeeded, double frameStartTime, double dspTimeBase, double totalLatency)
         {
             if (_bgmSamples == null || _bgmSamples.Length == 0) return;
 
@@ -258,13 +313,14 @@ namespace ADOFAIRenderer.Util.Audio
             // BGM Playback start time relative to dspTimeBase
             var time1 = dspTimeSong + separateCountdownOffset;
             var relativeTime1 = time1 - dspTimeBase;
+            var adjustedRelativeTime1 = relativeTime1 - totalLatency;
 
             var totalSamples = _bgmSamples.Length / _targetChannels;
 
             for (int s = 0; s < samplesNeeded; s++)
             {
                 double sampleTime = frameStartTime + (double)s / _targetSampleRate;
-                double clipTime = (sampleTime - relativeTime1) * pitch;
+                double clipTime = (sampleTime - adjustedRelativeTime1) * pitch;
 
                 if (clipTime >= 0 && clipTime < _bgmDuration)
                 {
@@ -287,7 +343,7 @@ namespace ADOFAIRenderer.Util.Audio
             }
         }
 
-        private void MixEffectSounds(float[] mixedBuffer, int samplesNeeded, double frameStartTime)
+        private void MixEffectSounds(float[] mixedBuffer, int samplesNeeded, double frameStartTime, double totalLatency)
         {
             for (var i = _activeEvents.Count - 1; i >= 0; i--)
             {
@@ -301,19 +357,21 @@ namespace ADOFAIRenderer.Util.Audio
 
                 var isSoundFinished = false;
                 var totalSamples = clipData.Samples.Length / _targetChannels;
+                double adjustedStartTime = ev.StartTime - totalLatency;
+                double adjustedEndTime = ev.EndTime >= 0 ? ev.EndTime - totalLatency : -1.0;
 
                 for (var s = 0; s < samplesNeeded; s++)
                 {
                     var sampleTime = frameStartTime + (double)s / _targetSampleRate;
 
                     // If it is a looping sound and has reached or exceeded its end time, stop playing.
-                    if (ev.EndTime >= 0 && sampleTime >= ev.EndTime)
+                    if (adjustedEndTime >= 0 && sampleTime >= adjustedEndTime)
                     {
                         isSoundFinished = true;
                         break;
                     }
 
-                    var elapsed = sampleTime - ev.StartTime;
+                    var elapsed = sampleTime - adjustedStartTime;
                     if (elapsed < 0) continue; // Sound hasn't started yet
 
                     var soundTime = elapsed * ev.Pitch;