some enhancements for MP3 playback

NAudio/Changes.xml

@@ -831,9 +831,12 @@
   <change>
     <version>1.2.135.0</version>
     <author>Mark Heath</author>
+    <date>13 Jun 2008</date>
     <desc>More unit tests for AudioClient</desc>
     <desc>Added option for WASAPI exclusive mode to NAudio Demo (not working yet)</desc>
     <desc>NAudioDemo can play MP3 files (not at low latency though)</desc>
     <desc>Position bar in NAudioDemo</desc>
+    <desc>Performance enhancements to WaveChannel32</desc>
+    <desc>MP3 playback less choppy</desc>
   </change>
 </changes>

NAudio/Wave/Compression/AcmStream.cs

@@ -13,6 +13,7 @@ namespace NAudio.Wave
         private IntPtr streamHandle;
         private IntPtr driverHandle;
         private AcmStreamHeader streamHeader;
+        private WaveFormat sourceFormat;
 
         /// <summary>
         /// Creates a new ACM stream to convert one format to another. Note that
@@ -22,16 +23,35 @@ namespace NAudio.Wave
         /// <param name="destFormat">The destination audio format</param>
         public AcmStream(WaveFormat sourceFormat, WaveFormat destFormat)
         {
-            int sourceBufferSize = sourceFormat.AverageBytesPerSecond;
-            sourceBufferSize -= (sourceBufferSize % sourceFormat.BlockAlign);
-            MmException.Try(AcmInterop.acmStreamOpen(out streamHandle, IntPtr.Zero, sourceFormat, destFormat, null, 0, 0, AcmStreamOpenFlags.NonRealTime), "acmStreamOpen");
-            streamHeader = new AcmStreamHeader(streamHandle, sourceBufferSize, SourceToDest(sourceBufferSize));
-            driverHandle = IntPtr.Zero;
+            try
+            {
+                streamHandle = IntPtr.Zero;
+                this.sourceFormat = sourceFormat;
+                int sourceBufferSize = Math.Max(16384, sourceFormat.AverageBytesPerSecond);
+                sourceBufferSize -= (sourceBufferSize % sourceFormat.BlockAlign);
+                MmException.Try(AcmInterop.acmStreamOpen(out streamHandle, IntPtr.Zero, sourceFormat, destFormat, null, 0, 0, AcmStreamOpenFlags.NonRealTime), "acmStreamOpen");
+                streamHeader = new AcmStreamHeader(streamHandle, sourceBufferSize, SourceToDest(sourceBufferSize));
+                driverHandle = IntPtr.Zero;
+            }
+            catch
+            {
+                // suppress the finalise and clean up resources
+                Dispose();
+                throw;
+            }
         }
 
+        /// <summary>
+        /// Creates a new ACM stream to convert one format to another, using a 
+        /// specified driver identified and wave filter
+        /// </summary>
+        /// <param name="driverId">the driver identifier</param>
+        /// <param name="sourceFormat">the source format</param>
+        /// <param name="waveFilter">the wave filter</param>
         public AcmStream(int driverId, WaveFormat sourceFormat, WaveFilter waveFilter)
         {
-            int sourceBufferSize = sourceFormat.AverageBytesPerSecond;
+            int sourceBufferSize = Math.Max(16384, sourceFormat.AverageBytesPerSecond);
+            this.sourceFormat = sourceFormat;
             sourceBufferSize -= (sourceBufferSize % sourceFormat.BlockAlign);
             MmException.Try(AcmInterop.acmDriverOpen(out driverHandle, driverId, 0), "acmDriverOpen");
             MmException.Try(AcmInterop.acmStreamOpen(out streamHandle, driverHandle,
@@ -104,6 +124,24 @@ namespace NAudio.Wave
             }
         }
 
+        /// <summary>
+        /// Converts the contents of the SourceBuffer into the DestinationBuffer
+        /// </summary>
+        /// <param name="bytesToConvert">The number of bytes in the SourceBuffer
+        /// that need to be converted</param>
+        /// <param name="sourceBytesConverted">The number of source bytes actually converted</param>
+        /// <returns>The number of converted bytes in the DestinationBuffer</returns>
+        public int Convert(int bytesToConvert, out int sourceBytesConverted)
+        {
+            if (bytesToConvert % sourceFormat.BlockAlign != 0)
+            {
+                System.Diagnostics.Debug.WriteLine(String.Format("NOT A WHOLE NUMBER OF BLOCKS", bytesToConvert));
+                bytesToConvert -= (bytesToConvert % sourceFormat.BlockAlign);
+            }
+
+            return streamHeader.Convert(bytesToConvert, out sourceBytesConverted);
+        }
+
         /// <summary>
         /// Converts the contents of the SourceBuffer into the DestinationBuffer
         /// </summary>
@@ -112,7 +150,13 @@ namespace NAudio.Wave
         /// <returns>The number of converted bytes in the DestinationBuffer</returns>
         public int Convert(int bytesToConvert)
         {
-            return streamHeader.Convert(bytesToConvert);
+            int sourceBytesConverted;
+            int destBytes = Convert(bytesToConvert, out sourceBytesConverted);
+            if (sourceBytesConverted != bytesToConvert)
+            {
+                throw new MmException(MmResult.NotSupported, "AcmStreamHeader.Convert didn't convert everything");
+            }
+            return destBytes;
         }
 
         /* Relevant only for async conversion streams

NAudio/Wave/Compression/AcmStreamHeader.cs

@@ -52,7 +52,7 @@ namespace NAudio.Wave
             }
         }
 
-        public int Convert(int bytesToConvert)
+        public int Convert(int bytesToConvert, out int sourceBytesConverted)
         {
             Prepare();
             try
@@ -63,13 +63,7 @@ namespace NAudio.Wave
                 MmException.Try(AcmInterop.acmStreamConvert(streamHandle, streamHeader, flags), "acmStreamConvert");
                 firstTime = false;
                 System.Diagnostics.Debug.Assert(streamHeader.destBufferLength == destBuffer.Length, "Codecs should not change dest buffer length");
-
-                if (streamHeader.sourceBufferLengthUsed != bytesToConvert)
-                {
-                    // TODO: a more appropriate exception type
-                    throw new MmException(MmResult.NotSupported, "AcmStreamHeader.Convert didn't convert everything");
-                }
-                int bytesConverted = streamHeader.destBufferLengthUsed;
+                sourceBytesConverted = streamHeader.sourceBufferLengthUsed;
             }
             finally
             {

NAudio/Wave/WaveOutputs/WasapiOut.cs

@@ -35,10 +35,15 @@ namespace NAudio.Wave
         public WasapiOut(AudioClientShareMode shareMode, int latency) :
             this(GetDefaultAudioEndpoint(), shareMode, latency)
         {
+
         }
 
         static MMDevice GetDefaultAudioEndpoint()
         {
+            if (Environment.OSVersion.Version.Major < 6)
+            {
+                throw new NotSupportedException("WASAPI supported only on Windows Vista and above");
+            }
             MMDeviceEnumerator enumerator = new MMDeviceEnumerator();
             return enumerator.GetDefaultAudioEndpoint(DataFlow.Render,Role.Console);
         }

NAudio/Wave/WaveStreams/WaveChannel32.cs

@@ -102,6 +102,20 @@ namespace NAudio.Wave
             }
         }
 
+        byte[] sourceBuffer;
+
+        /// <summary>
+        /// Helper function to avoid creating a new buffer every read
+        /// </summary>
+        byte[] GetSourceBuffer(int bytesRequired)
+        {
+            if (sourceBuffer == null || sourceBuffer.Length < bytesRequired)
+            {
+                sourceBuffer = new byte[Math.Min(sourceStream.WaveFormat.AverageBytesPerSecond,bytesRequired)];
+            }
+            return sourceBuffer;
+        }
+
         /// <summary>
         /// Reads bytes from this wave stream
         /// </summary>
@@ -124,7 +138,7 @@ namespace NAudio.Wave
                 if (sourceStream.WaveFormat.Channels == 1)
                 {
                     int sourceBytesRequired = (numBytes - bytesWritten) / 4;
-                    byte[] sourceBuffer = new byte[sourceBytesRequired];
+                    byte[] sourceBuffer = GetSourceBuffer(sourceBytesRequired);
                     int read = sourceStream.Read(sourceBuffer, 0, sourceBytesRequired);
                     MonoToStereo(destBuffer, offset + bytesWritten, sourceBuffer, read);
                     bytesWritten += (read * 4);
@@ -132,7 +146,7 @@ namespace NAudio.Wave
                 else
                 {
                     int sourceBytesRequired = (numBytes - bytesWritten) / 2;
-                    byte[] sourceBuffer = new byte[sourceBytesRequired];
+                    byte[] sourceBuffer = GetSourceBuffer(sourceBytesRequired);
                     int read = sourceStream.Read(sourceBuffer, 0, sourceBytesRequired);
                     AdjustVolume(destBuffer, offset + bytesWritten, sourceBuffer, read);
                     bytesWritten += (read * 2);
@@ -156,6 +170,7 @@ namespace NAudio.Wave
                 float* pfDestBuffer = (float*)pDestBuffer;
                 short* psSourceBuffer = (short*)pSourceBuffer;
 
+                // TODO:implement better panning laws. This one has 50% volume in middle
                 float leftVolume = (volume * (1 - pan) / 2.0f) / 32768f;
                 float rightVolume = (volume * (pan + 1) / 2.0f) / 32768f;
                 int samplesRead = bytesRead / 2;

NAudioDemo/AudioPlaybackForm.cs

@@ -49,7 +49,15 @@ namespace NAudioDemo
                 return;
             }
 
-            CreateWaveOut();
+            try
+            {
+                CreateWaveOut();
+            }
+            catch (Exception driverCreateException)
+            {
+                MessageBox.Show(String.Format("{0}", driverCreateException.Message));
+                return;
+            }
 
             WaveStream reader = CreateInputStream(fileName);
             trackBarPosition.Maximum = (int) reader.TotalTime.TotalSeconds;
@@ -62,10 +70,10 @@ namespace NAudioDemo
                 return;
             }
 
-            WaveMixerStream32 mixer = new WaveMixerStream32(inputs, false);
+            //WaveMixerStream32 mixer = new WaveMixerStream32(inputs, false);
             //Wave32To16Stream mixdown = new Wave32To16Stream(mixer);
-            mainOutputStream = mixer;
-            waveOut.Init(mixer);
+            mainOutputStream = inputs[0];
+            waveOut.Init(mainOutputStream);
             waveOut.Volume = volumeSlider1.Volume;
             groupBoxDriverModel.Enabled = false;
             waveOut.Play();