Audio ENCODING_IEC61937: enforce use of CHANNEL_OUT_STEREO

Prevent developers from using a channelMask that will fail.

Bug: 27721209
Change-Id: I87ad67caedaedf6ed2230165cb1687a2a0b74703
Signed-off-by: Phil Burk <philburk@google.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/media/java/android/media/AudioFormat.java b/media/java/android/media/AudioFormat.java
index abb6f4e9964c..a4484e757ac5 100644
--- a/media/java/android/media/AudioFormat.java
+++ b/media/java/android/media/AudioFormat.java
@@ -256,6 +256,11 @@ public final class AudioFormat implements Parcelable {
     public static final int ENCODING_AAC_HE_V2 = 12;
     /** Audio data format: compressed audio wrapped in PCM for HDMI
      * or S/PDIF passthrough.
+     * IEC61937 uses a stereo stream of 16-bit samples as the wrapper.
+     * So the channel mask for the track must be {@link #CHANNEL_OUT_STEREO}.
+     * Data should be written to the stream in a short[] array.
+     * If the data is written in a byte[] array then there may be endian problems
+     * on some platforms when converting to short internally.
      */
     public static final int ENCODING_IEC61937 = 13;
 
diff --git a/media/java/android/media/AudioTrack.java b/media/java/android/media/AudioTrack.java
index 2aac2b32bc62..c8c4e027d5ef 100644
--- a/media/java/android/media/AudioTrack.java
+++ b/media/java/android/media/AudioTrack.java
@@ -786,6 +786,15 @@ public class AudioTrack implements AudioRouting
         }
         mSampleRate = sampleRateInHz;
 
+        // IEC61937 is based on stereo. We could coerce it to stereo.
+        // But the application needs to know the stream is stereo so that
+        // it is encoded and played correctly. So better to just reject it.
+        if (audioFormat == AudioFormat.ENCODING_IEC61937
+                && channelConfig != AudioFormat.CHANNEL_OUT_STEREO) {
+            throw new IllegalArgumentException(
+                    "ENCODING_IEC61937 must be configured as CHANNEL_OUT_STEREO");
+        }
+
         //--------------
         // channel config
         mChannelConfiguration = channelConfig;