Allow outputting audio to a WAV file

Add TeeAudioProcessor that doesn't modify the input audio but writes it to an
AudioBufferSink, and WavFileAudioBufferSink for writing audio to a .wav file.

This is intended to be used for diagnostics and debugging.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=206717458

library/core/src/main/java/com/google/android/exoplayer2/audio/WavUtil.java

+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.audio;
+
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.util.Util;
+
+/** Utilities for handling WAVE files. */
+public final class WavUtil {
+
+  /** Four character code for "RIFF". */
+  public static final int RIFF_FOURCC = Util.getIntegerCodeForString("RIFF");
+  /** Four character code for "WAVE". */
+  public static final int WAVE_FOURCC = Util.getIntegerCodeForString("WAVE");
+  /** Four character code for "fmt ". */
+  public static final int FMT_FOURCC = Util.getIntegerCodeForString("fmt ");
+  /** Four character code for "data". */
+  public static final int DATA_FOURCC = Util.getIntegerCodeForString("data");
+
+  /** WAVE type value for integer PCM audio data. */
+  private static final int TYPE_PCM = 0x0001;
+  /** WAVE type value for float PCM audio data. */
+  private static final int TYPE_FLOAT = 0x0003;
+  /** WAVE type value for 8-bit ITU-T G.711 A-law audio data. */
+  private static final int TYPE_A_LAW = 0x0006;
+  /** WAVE type value for 8-bit ITU-T G.711 mu-law audio data. */
+  private static final int TYPE_MU_LAW = 0x0007;
+  /** WAVE type value for extended WAVE format. */
+  private static final int TYPE_WAVE_FORMAT_EXTENSIBLE = 0xFFFE;
+
+  /** Returns the WAVE type value for the given {@code encoding}. */
+  public static int getTypeForEncoding(@C.PcmEncoding int encoding) {
+    switch (encoding) {
+      case C.ENCODING_PCM_8BIT:
+      case C.ENCODING_PCM_16BIT:
+      case C.ENCODING_PCM_24BIT:
+      case C.ENCODING_PCM_32BIT:
+        return TYPE_PCM;
+      case C.ENCODING_PCM_A_LAW:
+        return TYPE_A_LAW;
+      case C.ENCODING_PCM_MU_LAW:
+        return TYPE_MU_LAW;
+      case C.ENCODING_PCM_FLOAT:
+        return TYPE_FLOAT;
+      case C.ENCODING_INVALID:
+      case Format.NO_VALUE:
+      default:
+        throw new IllegalArgumentException();
+    }
+  }
+
+  /** Returns the PCM encoding for the given WAVE {@code type} value. */
+  public static @C.PcmEncoding int getEncodingForType(int type, int bitsPerSample) {
+    switch (type) {
+      case TYPE_PCM:
+      case TYPE_WAVE_FORMAT_EXTENSIBLE:
+        return Util.getPcmEncoding(bitsPerSample);
+      case TYPE_FLOAT:
+        return bitsPerSample == 32 ? C.ENCODING_PCM_FLOAT : C.ENCODING_INVALID;
+      case TYPE_A_LAW:
+        return C.ENCODING_PCM_A_LAW;
+      case TYPE_MU_LAW:
+        return C.ENCODING_PCM_MU_LAW;
+      default:
+        return C.ENCODING_INVALID;
+    }
+  }
+
+  private WavUtil() {
+    // Prevent instantiation.
+  }
+}

library/core/src/main/java/com/google/android/exoplayer2/extractor/wav/WavHeaderReader.java

@@ -18,6 +18,7 @@ package com.google.android.exoplayer2.extractor.wav;
 import android.util.Log;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ParserException;
+import com.google.android.exoplayer2.audio.WavUtil;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
@@ -29,17 +30,6 @@ import java.io.IOException;
 
   private static final String TAG = "WavHeaderReader";
 
-  /** Integer PCM audio data. */
-  private static final int TYPE_PCM = 0x0001;
-  /** Float PCM audio data. */
-  private static final int TYPE_FLOAT = 0x0003;
-  /** 8-bit ITU-T G.711 A-law audio data. */
-  private static final int TYPE_A_LAW = 0x0006;
-  /** 8-bit ITU-T G.711 mu-law audio data. */
-  private static final int TYPE_MU_LAW = 0x0007;
-  /** Extended WAVE format. */
-  private static final int TYPE_WAVE_FORMAT_EXTENSIBLE = 0xFFFE;
-
   /**
    * Peeks and returns a {@code WavHeader}.
    *
@@ -58,21 +48,21 @@ import java.io.IOException;
 
     // Attempt to read the RIFF chunk.
     ChunkHeader chunkHeader = ChunkHeader.peek(input, scratch);
-    if (chunkHeader.id != Util.getIntegerCodeForString("RIFF")) {
+    if (chunkHeader.id != WavUtil.RIFF_FOURCC) {
       return null;
     }
 
     input.peekFully(scratch.data, 0, 4);
     scratch.setPosition(0);
     int riffFormat = scratch.readInt();
-    if (riffFormat != Util.getIntegerCodeForString("WAVE")) {
+    if (riffFormat != WavUtil.WAVE_FOURCC) {
       Log.e(TAG, "Unsupported RIFF format: " + riffFormat);
       return null;
     }
 
     // Skip chunks until we find the format chunk.
     chunkHeader = ChunkHeader.peek(input, scratch);
-    while (chunkHeader.id != Util.getIntegerCodeForString("fmt ")) {
+    while (chunkHeader.id != WavUtil.FMT_FOURCC) {
       input.advancePeekPosition((int) chunkHeader.size);
       chunkHeader = ChunkHeader.peek(input, scratch);
     }
@@ -93,28 +83,9 @@ import java.io.IOException;
           + blockAlignment);
     }
 
-    @C.PcmEncoding int encoding;
-    switch (type) {
-      case TYPE_PCM:
-      case TYPE_WAVE_FORMAT_EXTENSIBLE:
-        encoding = Util.getPcmEncoding(bitsPerSample);
-        break;
-      case TYPE_FLOAT:
-        encoding = bitsPerSample == 32 ? C.ENCODING_PCM_FLOAT : C.ENCODING_INVALID;
-        break;
-      case TYPE_A_LAW:
-        encoding = C.ENCODING_PCM_A_LAW;
-        break;
-      case TYPE_MU_LAW:
-        encoding = C.ENCODING_PCM_MU_LAW;
-        break;
-      default:
-        Log.e(TAG, "Unsupported WAV format type: " + type);
-        return null;
-    }
-
+    @C.PcmEncoding int encoding = WavUtil.getEncodingForType(type, bitsPerSample);
     if (encoding == C.ENCODING_INVALID) {
-      Log.e(TAG, "Unsupported WAV bit depth " + bitsPerSample + " for type " + type);
+      Log.e(TAG, "Unsupported WAV format: " + bitsPerSample + " bit/sample, type " + type);
       return null;
     }