Expose latency methods through AudioManager and AudioTrack.

There's a longer term plan to fix audio/video sync, but
this gets the Java level to parity with the native level,
and allows applications in Java to achieve sync in the
same way as the native media player. APIs are left as hidden
for now.

Bug: 9587132
Change-Id: Iaf70baac1ffb50ef48e03355163158568fbd0fe9

core/jni/android_media_AudioSystem.cpp

@@ -271,6 +271,17 @@ android_media_AudioSystem_getPrimaryOutputFrameCount(JNIEnv *env, jobject clazz)
     return (jint) AudioSystem::getPrimaryOutputFrameCount();
 }
 
+static jint
+android_media_AudioSystem_getOutputLatency(JNIEnv *env, jobject clazz, jint stream)
+{
+    uint32_t afLatency;
+    if (AudioSystem::getOutputLatency(&afLatency, static_cast <audio_stream_type_t>(stream))
+            != NO_ERROR) {
+        afLatency = -1;
+    }
+    return (jint) afLatency;
+}
+
 // ----------------------------------------------------------------------------
 
 static JNINativeMethod gMethods[] = {
@@ -296,6 +307,7 @@ static JNINativeMethod gMethods[] = {
     {"getDevicesForStream", "(I)I",     (void *)android_media_AudioSystem_getDevicesForStream},
     {"getPrimaryOutputSamplingRate", "()I", (void *)android_media_AudioSystem_getPrimaryOutputSamplingRate},
     {"getPrimaryOutputFrameCount",   "()I", (void *)android_media_AudioSystem_getPrimaryOutputFrameCount},
+    {"getOutputLatency",    "(I)I",     (void *)android_media_AudioSystem_getOutputLatency},
 };
 
 int register_android_media_AudioSystem(JNIEnv *env)

core/jni/android_media_AudioTrack.cpp

@@ -727,6 +727,19 @@ static jint android_media_AudioTrack_get_position(JNIEnv *env,  jobject thiz) {
 }
 
 
+// ----------------------------------------------------------------------------
+static jint android_media_AudioTrack_get_latency(JNIEnv *env,  jobject thiz) {
+    sp<AudioTrack> lpTrack = getAudioTrack(env, thiz);
+
+    if (lpTrack == NULL) {
+        jniThrowException(env, "java/lang/IllegalStateException",
+            "Unable to retrieve AudioTrack pointer for latency()");
+        return AUDIOTRACK_ERROR;
+    }
+    return (jint)lpTrack->latency();
+}
+
+
 // ----------------------------------------------------------------------------
 static jint android_media_AudioTrack_set_loop(JNIEnv *env,  jobject thiz,
         jint loopStart, jint loopEnd, jint loopCount) {
@@ -854,6 +867,7 @@ static JNINativeMethod gMethods[] = {
                              "()I",      (void *)android_media_AudioTrack_get_pos_update_period},
     {"native_set_position",  "(I)I",     (void *)android_media_AudioTrack_set_position},
     {"native_get_position",  "()I",      (void *)android_media_AudioTrack_get_position},
+    {"native_get_latency",   "()I",      (void *)android_media_AudioTrack_get_latency},
     {"native_set_loop",      "(III)I",   (void *)android_media_AudioTrack_set_loop},
     {"native_reload_static", "()I",      (void *)android_media_AudioTrack_reload},
     {"native_get_output_sample_rate",

media/java/android/media/AudioManager.java

@@ -2553,4 +2553,15 @@ public class AudioManager {
         }
     }
 
+    /**
+     * Returns the estimated latency for the given stream type in milliseconds.
+     *
+     * DO NOT UNHIDE. The existing approach for doing A/V sync has too many problems. We need
+     * a better solution.
+     * @hide
+     */
+    public int getOutputLatency(int streamType) {
+        return AudioSystem.getOutputLatency(streamType);
+    }
+
 }

media/java/android/media/AudioSystem.java

@@ -401,5 +401,6 @@ public class AudioSystem
     // helpers for android.media.AudioManager.getProperty(), see description there for meaning
     public static native int getPrimaryOutputSamplingRate();
     public static native int getPrimaryOutputFrameCount();
+    public static native int getOutputLatency(int stream);
 
 }

media/java/android/media/AudioTrack.java

@@ -627,6 +627,18 @@ public class AudioTrack
         return native_get_position();
     }
 
+    /**
+     * Returns this track's estimated latency in milliseconds. This includes the latency due
+     * to AudioTrack buffer size, AudioMixer (if any) and audio hardware driver.
+     *
+     * DO NOT UNHIDE. The existing approach for doing A/V sync has too many problems. We need
+     * a better solution.
+     * @hide
+     */
+    public int getLatency() {
+        return native_get_latency();
+    }
+
     /**
      *  Returns the hardware output sample rate
      */
@@ -1256,6 +1268,8 @@ public class AudioTrack
     private native final int native_set_position(int position);
     private native final int native_get_position();
 
+    private native final int native_get_latency();
+
     private native final int native_set_loop(int start, int end, int loopCount);
 
     static private native final int native_get_output_sample_rate(int streamType);