diff --git a/include/media/AudioPolicyHelper.h b/include/media/AudioPolicyHelper.h
index f4afd45..3ed0b74 100644
--- a/include/media/AudioPolicyHelper.h
+++ b/include/media/AudioPolicyHelper.h
@@ -18,7 +18,7 @@
 
 #include <system/audio.h>
 
-audio_stream_type_t audio_attributes_to_stream_type(const audio_attributes_t *attr)
+static audio_stream_type_t audio_attributes_to_stream_type(const audio_attributes_t *attr)
 {
     // flags to stream type mapping
     if ((attr->flags & AUDIO_FLAG_AUDIBILITY_ENFORCED) == AUDIO_FLAG_AUDIBILITY_ENFORCED) {
@@ -61,4 +61,55 @@
     }
 }
 
+static void stream_type_to_audio_attributes(audio_stream_type_t streamType,
+                                     audio_attributes_t *attr) {
+    attr->flags = 0x0;
+
+    switch (streamType) {
+    case AUDIO_STREAM_DEFAULT:
+    case AUDIO_STREAM_MUSIC:
+        attr->content_type = AUDIO_CONTENT_TYPE_MUSIC;
+        attr->usage = AUDIO_USAGE_MEDIA;
+        break;
+    case AUDIO_STREAM_VOICE_CALL:
+        attr->content_type = AUDIO_CONTENT_TYPE_SPEECH;
+        attr->usage = AUDIO_USAGE_VOICE_COMMUNICATION;
+        break;
+    case AUDIO_STREAM_ENFORCED_AUDIBLE:
+        attr->flags  |= AUDIO_FLAG_AUDIBILITY_ENFORCED;
+        // intended fall through, attributes in common with STREAM_SYSTEM
+    case AUDIO_STREAM_SYSTEM:
+        attr->content_type = AUDIO_CONTENT_TYPE_SONIFICATION;
+        attr->usage = AUDIO_USAGE_ASSISTANCE_SONIFICATION;
+        break;
+    case AUDIO_STREAM_RING:
+        attr->content_type = AUDIO_CONTENT_TYPE_SONIFICATION;
+        attr->usage = AUDIO_USAGE_NOTIFICATION_TELEPHONY_RINGTONE;
+        break;
+    case AUDIO_STREAM_ALARM:
+        attr->content_type = AUDIO_CONTENT_TYPE_SONIFICATION;
+        attr->usage = AUDIO_USAGE_ALARM;
+        break;
+    case AUDIO_STREAM_NOTIFICATION:
+        attr->content_type = AUDIO_CONTENT_TYPE_SONIFICATION;
+        attr->usage = AUDIO_USAGE_NOTIFICATION;
+        break;
+    case AUDIO_STREAM_BLUETOOTH_SCO:
+        attr->content_type = AUDIO_CONTENT_TYPE_SPEECH;
+        attr->usage = AUDIO_USAGE_VOICE_COMMUNICATION;
+        attr->flags |= AUDIO_FLAG_SCO;
+        break;
+    case AUDIO_STREAM_DTMF:
+        attr->content_type = AUDIO_CONTENT_TYPE_SONIFICATION;
+        attr->usage = AUDIO_USAGE_VOICE_COMMUNICATION_SIGNALLING;
+        break;
+    case AUDIO_STREAM_TTS:
+        attr->content_type = AUDIO_CONTENT_TYPE_SPEECH;
+        attr->usage = AUDIO_USAGE_ASSISTANCE_ACCESSIBILITY;
+        break;
+    default:
+        ALOGE("invalid stream type %d when converting to attributes", streamType);
+    }
+}
+
 #endif //AUDIO_POLICY_HELPER_H_
diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index 1614525..7f1afb3 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -215,7 +215,10 @@
                                         audio_channel_mask_t channelMask = AUDIO_CHANNEL_OUT_STEREO,
                                         audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
                                         const audio_offload_info_t *offloadInfo = NULL);
-    static audio_io_handle_t getOutputForAttr(const audio_attributes_t *attr,
+    static status_t getOutputForAttr(const audio_attributes_t *attr,
+                                        audio_io_handle_t *output,
+                                        audio_session_t session,
+                                        audio_stream_type_t *stream,
                                         uint32_t samplingRate = 0,
                                         audio_format_t format = AUDIO_FORMAT_DEFAULT,
                                         audio_channel_mask_t channelMask = AUDIO_CHANNEL_OUT_STEREO,
@@ -223,11 +226,13 @@
                                         const audio_offload_info_t *offloadInfo = NULL);
     static status_t startOutput(audio_io_handle_t output,
                                 audio_stream_type_t stream,
-                                int session);
+                                audio_session_t session);
     static status_t stopOutput(audio_io_handle_t output,
                                audio_stream_type_t stream,
-                               int session);
-    static void releaseOutput(audio_io_handle_t output);
+                               audio_session_t session);
+    static void releaseOutput(audio_io_handle_t output,
+                              audio_stream_type_t stream,
+                              audio_session_t session);
 
     // Client must successfully hand off the handle reference to AudioFlinger via openRecord(),
     // or release it with releaseInput().
@@ -235,7 +240,7 @@
                                     uint32_t samplingRate,
                                     audio_format_t format,
                                     audio_channel_mask_t channelMask,
-                                    int sessionId,
+                                    audio_session_t sessionId,
                                     audio_input_flags_t);
 
     static status_t startInput(audio_io_handle_t input,
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index b5256f0..fd51b8f 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -239,6 +239,9 @@
      * Parameters not listed in the AudioTrack constructors above:
      *
      * threadCanCallJava:  Whether callbacks are made from an attached thread and thus can call JNI.
+     *
+     * Internal state post condition:
+     *      (mStreamType == AUDIO_STREAM_DEFAULT) implies this AudioTrack has valid attributes
      */
             status_t    set(audio_stream_type_t streamType,
                             uint32_t sampleRate,
@@ -273,7 +276,7 @@
 
     /* getters, see constructors and set() */
 
-            audio_stream_type_t streamType() const { return mStreamType; }
+            audio_stream_type_t streamType() const;
             audio_format_t format() const   { return mFormat; }
 
     /* Return frame size in bytes, which for linear PCM is
@@ -598,9 +601,6 @@
             AudioTrack& operator = (const AudioTrack& other);
 
             void        setAttributesFromStreamType(audio_stream_type_t streamType);
-            void        setStreamTypeFromAttributes(audio_attributes_t& aa);
-    /* paa is guaranteed non-NULL */
-            bool        isValidAttributes(const audio_attributes_t *paa);
 
     /* a small internal class to handle the callback */
     class AudioTrackThread : public Thread
@@ -688,7 +688,8 @@
 
     // constant after constructor or set()
     audio_format_t          mFormat;                // as requested by client, not forced to 16-bit
-    audio_stream_type_t     mStreamType;
+    audio_stream_type_t     mStreamType;            // mStreamType == AUDIO_STREAM_DEFAULT implies
+                                                    // this AudioTrack has valid attributes
     uint32_t                mChannelCount;
     audio_channel_mask_t    mChannelMask;
     sp<IMemory>             mSharedBuffer;
diff --git a/include/media/IAudioPolicyService.h b/include/media/IAudioPolicyService.h
index 16fe9cf..2f30304 100644
--- a/include/media/IAudioPolicyService.h
+++ b/include/media/IAudioPolicyService.h
@@ -56,24 +56,29 @@
                                         audio_channel_mask_t channelMask = 0,
                                         audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
                                         const audio_offload_info_t *offloadInfo = NULL) = 0;
-    virtual audio_io_handle_t getOutputForAttr(const audio_attributes_t *attr,
-                                            uint32_t samplingRate = 0,
-                                            audio_format_t format = AUDIO_FORMAT_DEFAULT,
-                                            audio_channel_mask_t channelMask = 0,
-                                            audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
-                                            const audio_offload_info_t *offloadInfo = NULL) = 0;
+    virtual status_t getOutputForAttr(const audio_attributes_t *attr,
+                                        audio_io_handle_t *output,
+                                        audio_session_t session,
+                                        audio_stream_type_t *stream,
+                                        uint32_t samplingRate = 0,
+                                        audio_format_t format = AUDIO_FORMAT_DEFAULT,
+                                        audio_channel_mask_t channelMask = 0,
+                                        audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
+                                        const audio_offload_info_t *offloadInfo = NULL) = 0;
     virtual status_t startOutput(audio_io_handle_t output,
                                  audio_stream_type_t stream,
-                                 int session = 0) = 0;
+                                 audio_session_t session) = 0;
     virtual status_t stopOutput(audio_io_handle_t output,
                                 audio_stream_type_t stream,
-                                int session = 0) = 0;
-    virtual void releaseOutput(audio_io_handle_t output) = 0;
+                                audio_session_t session) = 0;
+    virtual void releaseOutput(audio_io_handle_t output,
+                               audio_stream_type_t stream,
+                               audio_session_t session) = 0;
     virtual audio_io_handle_t getInput(audio_source_t inputSource,
                                     uint32_t samplingRate,
                                     audio_format_t format,
                                     audio_channel_mask_t channelMask,
-                                    int audioSession,
+                                    audio_session_t audioSession,
                                     audio_input_flags_t flags) = 0;
     virtual status_t startInput(audio_io_handle_t input,
                                 audio_session_t session) = 0;