i2s: Allow recording to multiple files

This simply abuses the PCMEncoder class to change the output filename
using an indexing scheme each time it is restarted using the CSR.

Change-Id: Ic2d393b5c2c6a732d36de5869540b51d251f9a7c

shodan_infrastructure/MatchaI2S.cs

diff --git a/shodan_infrastructure/MatchaI2S.cs b/shodan_infrastructure/MatchaI2S.cs
index be3a3da..bee1cbf 100644
--- a/shodan_infrastructure/MatchaI2S.cs
+++ b/shodan_infrastructure/MatchaI2S.cs
@@ -16,6 +16,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Text;
@@ -210,7 +211,8 @@
             this.Log(LogLevel.Info, "Starting playback.");
 
             encoder = new PCMEncoder(SampleSizeBits, SampleFrequencyHz, NumChannels, false);
-            encoder.Output = OutputFile;
+            encoder.Output = OutputFile + String.Format(".{0}.{1:d4}",
+                    Process.GetCurrentProcess().Id, outputFileIdx++);
             encoder.SetBufferingBySamplesCount(1);
 
             txThread = machine.ObtainManagedThread(TransmitFrame, SampleFrequencyHz);
@@ -420,6 +422,7 @@
 
         private int mappedRxTriggerLevel;
         private int mappedTxTriggerLevel;
+        private int outputFileIdx;
 
         private IManagedThread rxThread;
         private IManagedThread txThread;