diff --git a/audio/6.0/IStreamOutEventCallback.hal b/audio/6.0/IStreamOutEventCallback.hal
index de17d73..9c88713 100644
--- a/audio/6.0/IStreamOutEventCallback.hal
+++ b/audio/6.0/IStreamOutEventCallback.hal
@@ -25,11 +25,116 @@
     /**
      * Codec format changed.
      *
+     * onCodecFormatChanged returns an AudioMetadata object in read-only ByteString format.
+     * It represents the most recent codec format decoded by a HW audio decoder.
+     *
+     * Codec format is an optional message from HW audio decoders. It serves to
+     * notify the application about the codec format and audio objects contained
+     * within the compressed audio stream for control, informational,
+     * and display purposes.
+     *
+     * audioMetadata ByteString is convertible to an AudioMetadata object through
+     * both a C++ and a C API present in Metadata.h [1], or through a Java API present
+     * in AudioMetadata.java [2].
+     *
+     * The ByteString format is a stable format used for parcelling (marshalling) across
+     * JNI, AIDL, and HIDL interfaces.  The test for R compatibility for native marshalling
+     * is TEST(metadata_tests, compatibility_R) [3].  The test for R compatibility for JNI
+     * marshalling is android.media.cts.AudioMetadataTest#testCompatibilityR [4].
+     *
+     * R (audio HAL 6.0) defined keys are as follows [2]:
+     * "bitrate", int32
+     * "channel-mask", int32
+     * "mime", string
+     * "sample-rate", int32
+     * "bit-width", int32
+     * "has-atmos", int32
+     * "audio-encoding", int32
+     *
+     * Parceling Format:
+     * All values are native endian order. [1]
+     *
+     * using type_size_t = uint32_t;
+     * using index_size_t = uint32_t;
+     * using datum_size_t = uint32_t;
+     *
+     * Permitted type indexes are
+     * TYPE_NONE = 0, // Reserved
+     * TYPE_INT32 = 1,
+     * TYPE_INT64 = 2,
+     * TYPE_FLOAT = 3,
+     * TYPE_DOUBLE = 4,
+     * TYPE_STRING = 5,
+     * TYPE_DATA = 6,  // A data table of <String, Datum>
+     *
+     * Datum = {
+     *           (type_size_t)  Type (the type index from type_as_value<T>.)
+     *           (datum_size_t) Size (size of the Payload)
+     *           (byte string)  Payload<Type>
+     *         }
+     *
+     * The data is specified in native endian order.
+     * Since the size of the Payload is always present, unknown types may be skipped.
+     *
+     * Payload<Fixed-size Primitive_Value>
+     * [ sizeof(Primitive_Value) in raw bytes ]
+     *
+     * Example of Payload<Int32> of 123:
+     * Payload<Int32>
+     * [ value of 123                   ] =  0x7b 0x00 0x00 0x00       123
+     *
+     * Payload<String>
+     * [ (index_size_t) length, not including zero terminator.]
+     * [ (length) raw bytes ]
+     *
+     * Example of Payload<String> of std::string("hi"):
+     * [ (index_size_t) length          ] = 0x02 0x00 0x00 0x00        2 strlen("hi")
+     * [ raw bytes "hi"                 ] = 0x68 0x69                  "hi"
+     *
+     * Payload<Data>
+     * [ (index_size_t) entries ]
+     * [ raw bytes   (entry 1) Key   (Payload<String>)
+     *                         Value (Datum)
+     *                ...  (until #entries) ]
+     *
+     * Example of Payload<Data> of {{"hello", "world"},
+     *                              {"value", (int32_t)1000}};
+     * [ (index_size_t) #entries        ] = 0x02 0x00 0x00 0x00        2 entries
+     *    Key (Payload<String>)
+     *    [ index_size_t length         ] = 0x05 0x00 0x00 0x00        5 strlen("hello")
+     *    [ raw bytes "hello"           ] = 0x68 0x65 0x6c 0x6c 0x6f   "hello"
+     *    Value (Datum)
+     *    [ (type_size_t) type          ] = 0x05 0x00 0x00 0x00        5 (TYPE_STRING)
+     *    [ (datum_size_t) size         ] = 0x09 0x00 0x00 0x00        sizeof(index_size_t) +
+     *                                                                 strlen("world")
+     *       Payload<String>
+     *       [ (index_size_t) length    ] = 0x05 0x00 0x00 0x00        5 strlen("world")
+     *       [ raw bytes "world"        ] = 0x77 0x6f 0x72 0x6c 0x64   "world"
+     *    Key (Payload<String>)
+     *    [ index_size_t length         ] = 0x05 0x00 0x00 0x00        5 strlen("value")
+     *    [ raw bytes "value"           ] = 0x76 0x61 0x6c 0x75 0x65   "value"
+     *    Value (Datum)
+     *    [ (type_size_t) type          ] = 0x01 0x00 0x00 0x00        1 (TYPE_INT32)
+     *    [ (datum_size_t) size         ] = 0x04 0x00 0x00 0x00        4 sizeof(int32_t)
+     *        Payload<Int32>
+     *        [ raw bytes 1000          ] = 0xe8 0x03 0x00 0x00        1000
+     *
+     * The contents of audioMetadata is a Payload<Data>.
+     * An implementation dependent detail is that the Keys are always
+     * stored sorted, so the byte string representation generated is unique.
+     *
+     * Vendor keys are allowed for informational and debugging purposes.
+     * Vendor keys should consist of the vendor company name followed
+     * by a dot; for example, "vendorCompany.someVolume" [2].
+     *
+     * [1] system/media/audio_utils/include/audio_utils/Metadata.h
+     * [2] frameworks/base/media/java/android/media/AudioMetadata.java
+     * [3] system/media/audio_utils/tests/metadata_tests.cpp
+     * [4] cts/tests/tests/media/src/android/media/cts/AudioMetadataTest.java
+     *
      * @param audioMetadata is a buffer containing decoded format changes
      *     reported by codec. The buffer contains data that can be transformed
-     *     to audio metadata, which is a C++ object based map. See
-     *     `system/media/audio_utils/include/audio_utils/Metadata.h` for
-     *     more details.
+     *     to audio metadata, which is a C++ object based map.
      */
     oneway onCodecFormatChanged(vec<uint8_t> audioMetadata);
 };
diff --git a/current.txt b/current.txt
index d2b7206..edf96b2 100644
--- a/current.txt
+++ b/current.txt
@@ -619,6 +619,7 @@
 164826a380f4c1700183003f62d7532e367b67381c30ea44f946c0cf00008f85 android.hardware.audio@6.0::IStreamOut
 997fdaad7a9d17ee7e01feb7031a753e2365e72ad30b11d950e9183fabdf3844 android.hardware.audio@6.0::IStreamOutCallback
 e7ca0db9a1098210f327a9b152fa6afe6bf019c41e5264c64829d04d50c0a526 android.hardware.audio@6.0::IStreamOutEventCallback
+aa2211abd803e03d05ea11c18749db068f785fe026f8d99bce64bd764f63d194 android.hardware.audio@6.0::IStreamOutEventCallback  # b/150175043
 822369cf4dc16a6f6b9622bcf86cbdc0b692dc82193fc15e967767175cbfdd8f android.hardware.audio@6.0::types
 bee662c62d997d8065e2bcb5c1e7a9578931f22ce28fd02c219fdb4d0630abf7 android.hardware.audio.common@6.0::types
 525bec6b44f1103869c269a128d51b8dccd73af5340ba863c8886c68357c7faf android.hardware.audio.effect@6.0::IAcousticEchoCancelerEffect