Adjust incorrect looking max-channel counts

Issue: #2940

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=159099602

Author: ojw28

library/core/src/main/java/com/google/android/exoplayer2/extractor/flv/AudioTagPayloadReader.java

@@ -67,7 +67,7 @@ protected boolean parseHeader(ParsableByteArray data) throws UnsupportedFormatEx
         hasOutputFormat = true;
       } else if (audioFormat == AUDIO_FORMAT_ALAW || audioFormat == AUDIO_FORMAT_ULAW) {
         String type = audioFormat == AUDIO_FORMAT_ALAW ? MimeTypes.AUDIO_ALAW
-            : MimeTypes.AUDIO_ULAW;
+            : MimeTypes.AUDIO_MLAW;
         int pcmEncoding = (header & 0x01) == 1 ? C.ENCODING_PCM_16BIT : C.ENCODING_PCM_8BIT;
         Format format = Format.createAudioSampleFormat(null, type, null, Format.NO_VALUE,
             Format.NO_VALUE, 1, 8000, pcmEncoding, null, null, 0, null);

library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecInfo.java

@@ -274,7 +274,9 @@ public boolean isAudioChannelCountSupportedV21(int channelCount) {
       logNoSupport("channelCount.aCaps");
       return false;
     }
-    if (audioCapabilities.getMaxInputChannelCount() < channelCount) {
+    int maxInputChannelCount = adjustMaxInputChannelCount(name, mimeType,
+        audioCapabilities.getMaxInputChannelCount());
+    if (maxInputChannelCount < channelCount) {
       logNoSupport("channelCount.support, " + channelCount);
       return false;
     }
@@ -291,6 +293,40 @@ private void logAssumedSupport(String message) {
         + Util.DEVICE_DEBUG_INFO + "]");
   }
 
+  private static int adjustMaxInputChannelCount(String name, String mimeType, int maxChannelCount) {
+    if (maxChannelCount > 1 || (Util.SDK_INT >= 26 && maxChannelCount > 0)) {
+      // The maximum channel count looks like it's been set correctly.
+      return maxChannelCount;
+    }
+    if (MimeTypes.AUDIO_MPEG.equals(mimeType)
+        || MimeTypes.AUDIO_AMR_NB.equals(mimeType)
+        || MimeTypes.AUDIO_AMR_WB.equals(mimeType)
+        || MimeTypes.AUDIO_AAC.equals(mimeType)
+        || MimeTypes.AUDIO_VORBIS.equals(mimeType)
+        || MimeTypes.AUDIO_OPUS.equals(mimeType)
+        || MimeTypes.AUDIO_RAW.equals(mimeType)
+        || MimeTypes.AUDIO_FLAC.equals(mimeType)
+        || MimeTypes.AUDIO_ALAW.equals(mimeType)
+        || MimeTypes.AUDIO_MLAW.equals(mimeType)
+        || MimeTypes.AUDIO_MSGSM.equals(mimeType)) {
+      // Platform code should have set a default.
+      return maxChannelCount;
+    }
+    // The maximum channel count looks incorrect. Adjust it to an assumed default.
+    int assumedMaxChannelCount;
+    if (MimeTypes.AUDIO_AC3.equals(mimeType)) {
+      assumedMaxChannelCount = 6;
+    } else if (MimeTypes.AUDIO_E_AC3.equals(mimeType)) {
+      assumedMaxChannelCount = 16;
+    } else {
+      // Default to the platform limit, which is 30.
+      assumedMaxChannelCount = 30;
+    }
+    Log.w(TAG, "AssumedMaxChannelAdjustment: " + name + ", [" + maxChannelCount + " to "
+        + assumedMaxChannelCount + "]");
+    return assumedMaxChannelCount;
+  }
+
   private static boolean isAdaptive(CodecCapabilities capabilities) {
     return Util.SDK_INT >= 19 && isAdaptiveV19(capabilities);
   }

library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java

@@ -48,7 +48,7 @@ public final class MimeTypes {
   public static final String AUDIO_MPEG_L2 = BASE_TYPE_AUDIO + "/mpeg-L2";
   public static final String AUDIO_RAW = BASE_TYPE_AUDIO + "/raw";
   public static final String AUDIO_ALAW = BASE_TYPE_AUDIO + "/g711-alaw";
-  public static final String AUDIO_ULAW = BASE_TYPE_AUDIO + "/g711-mlaw";
+  public static final String AUDIO_MLAW = BASE_TYPE_AUDIO + "/g711-mlaw";
   public static final String AUDIO_AC3 = BASE_TYPE_AUDIO + "/ac3";
   public static final String AUDIO_E_AC3 = BASE_TYPE_AUDIO + "/eac3";
   public static final String AUDIO_TRUEHD = BASE_TYPE_AUDIO + "/true-hd";
@@ -59,8 +59,9 @@ public final class MimeTypes {
   public static final String AUDIO_OPUS = BASE_TYPE_AUDIO + "/opus";
   public static final String AUDIO_AMR_NB = BASE_TYPE_AUDIO + "/3gpp";
   public static final String AUDIO_AMR_WB = BASE_TYPE_AUDIO + "/amr-wb";
-  public static final String AUDIO_FLAC = BASE_TYPE_AUDIO + "/x-flac";
+  public static final String AUDIO_FLAC = BASE_TYPE_AUDIO + "/flac";
   public static final String AUDIO_ALAC = BASE_TYPE_AUDIO + "/alac";
+  public static final String AUDIO_MSGSM = BASE_TYPE_AUDIO + "/gsm";
   public static final String AUDIO_UNKNOWN = BASE_TYPE_AUDIO + "/x-unknown";
 
   public static final String TEXT_VTT = BASE_TYPE_TEXT + "/vtt";