AudioTrack: fix getPlaybackHeadPosition and write

this fixes audio sync in exoplayer

src/api-impl-jni/audio/android_media_AudioTrack.c

@@ -217,7 +217,7 @@ JNIEXPORT void JNICALL Java_android_media_AudioTrack_native_1play(JNIEnv *env, j
 /*--↑*/
 }
 
-JNIEXPORT jint JNICALL Java_android_media_AudioTrack_native_1write(JNIEnv *env, jobject this, jbyteArray audioData, jint offsetInBytes, jint frames_to_write)
+JNIEXPORT jint JNICALL Java_android_media_AudioTrack_native_1write(JNIEnv *env, jobject this, jbyteArray audio_data, jint offset_in_bytes, jint frames_to_write)
 {
 	int ret;
 
@@ -225,9 +225,9 @@ JNIEXPORT jint JNICALL Java_android_media_AudioTrack_native_1write(JNIEnv *env,
 
 	snd_pcm_sframes_t frames_written;
 
-	jbyte *buffer = _GET_BYTE_ARRAY_ELEMENTS(audioData);
+	jbyte *buffer = _GET_BYTE_ARRAY_ELEMENTS(audio_data);
 
-	ret = frames_written = snd_pcm_writei(pcm_handle, buffer, frames_to_write);
+	ret = frames_written = snd_pcm_writei(pcm_handle, buffer + offset_in_bytes, frames_to_write);
 	if (ret < 0) {
 		if (ret == -EPIPE) {
 			printf("XRUN.\n");
@@ -239,7 +239,7 @@ JNIEXPORT jint JNICALL Java_android_media_AudioTrack_native_1write(JNIEnv *env,
 
 //	printf("::::> tried to write %d frames, actually wrote %d frames.\n", frames_to_write, frames_written);
 
-	_RELEASE_BYTE_ARRAY_ELEMENTS(audioData, buffer);
+	_RELEASE_BYTE_ARRAY_ELEMENTS(audio_data, buffer);
 	return frames_written;
 }
 
@@ -254,3 +254,12 @@ JNIEXPORT void JNICALL Java_android_media_AudioTrack_native_1release(JNIEnv *env
 	snd_pcm_t *pcm_handle = _PTR(_GET_LONG_FIELD(this, "pcm_handle"));
 	snd_pcm_close(pcm_handle);
 }
+
+JNIEXPORT jint JNICALL Java_android_media_AudioTrack_native_1getPlaybackHeadPosition(JNIEnv *env, jobject this)
+{
+	snd_pcm_t *pcm_handle = _PTR(_GET_LONG_FIELD(this, "pcm_handle"));
+	snd_pcm_sframes_t delay;
+	snd_pcm_delay(pcm_handle, &delay);
+
+	return delay;
+}

src/api-impl-jni/generated_headers/android_media_AudioTrack.h

@@ -7,6 +7,8 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+#undef android_media_AudioTrack_ERROR_BAD_VALUE
+#define android_media_AudioTrack_ERROR_BAD_VALUE -2L
 #undef android_media_AudioTrack_PLAYSTATE_STOPPED
 #define android_media_AudioTrack_PLAYSTATE_STOPPED 1L
 #undef android_media_AudioTrack_PLAYSTATE_PAUSED
@@ -29,6 +31,14 @@ JNIEXPORT void JNICALL Java_android_media_AudioTrack_native_1constructor
 JNIEXPORT jint JNICALL Java_android_media_AudioTrack_getMinBufferSize
   (JNIEnv *, jclass, jint, jint, jint);
 
+/*
+ * Class:     android_media_AudioTrack
+ * Method:    native_getPlaybackHeadPosition
+ * Signature: ()I
+ */
+JNIEXPORT jint JNICALL Java_android_media_AudioTrack_native_1getPlaybackHeadPosition
+  (JNIEnv *, jobject);
+
 /*
  * Class:     android_media_AudioTrack
  * Method:    native_play

src/api-impl/android/media/AudioTrack.java

@@ -6,6 +6,8 @@ public class AudioTrack {
 		void onPeriodicNotification(AudioTrack track);
 	}
 
+	public static final int ERROR_BAD_VALUE = -2; // basically EINVAL
+
 	public static final int PLAYSTATE_STOPPED = 1;
 	public static final int PLAYSTATE_PAUSED  = 2;
 	public static final int PLAYSTATE_PLAYING = 3;
@@ -67,7 +69,7 @@ public class AudioTrack {
 	}
 
 	public int setPositionNotificationPeriod(int periodInFrames) {
-		System.out.println("\n\n\nsetPositionNotificationPeriod(" + periodInFrames + "); called\n\n\n\n");
+		System.out.println("\n\nAudioTrack.nsetPositionNotificationPeriod(" + periodInFrames + "); called\n\n\n\n");
 		return 0; // SUCCESS
 	}
 
@@ -82,16 +84,16 @@ public class AudioTrack {
 	}
 
 	public void stop() {
-		System.out.println("calling stop(), how did this not get reported before DIDREEEEEEEEEEEEEEEEEEEEEEEEE\n");
+		System.out.println("STUB: AudioTrack.stop()\n");
 		playbackState = PLAYSTATE_STOPPED;
 	}
 
 	public void flush() {
-		System.out.println("calling flush(), how did this not get reported before DIDREEEEEEEEEEEEEEEEEEEEEEEEE\n");
+		System.out.println("STUB: AudioTrack.flush()\n");
 	}
 
 	public void release() {
-		System.out.println("calling release(), how did this not get reported before DIDREEEEEEEEEEEEEEEEEEEEEEEEE\n");
+		System.out.println("calling AudioTrack.release()\n");
 		native_release();
 	}
 
@@ -100,6 +102,14 @@ public class AudioTrack {
 	}
 
 	public int write(byte[] audioData, int offsetInBytes, int sizeInBytes) {
+		/* sanity check the parameters before calling native_write */
+		if ((audioData == null)
+		    || (offsetInBytes < 0) || (sizeInBytes < 0)
+		    || (offsetInBytes + sizeInBytes < 0)
+		    || (offsetInBytes + sizeInBytes > audioData.length)) {
+			return ERROR_BAD_VALUE;
+		}
+
 		int framesToWrite = sizeInBytes / channels / 2;  // 2 means PCM16
 		int ret = native_write(audioData, offsetInBytes, framesToWrite);
 		if (ret > 0) {
@@ -131,9 +141,10 @@ public class AudioTrack {
 	}
 
 	public int getPlaybackHeadPosition() {
-		return playbackHeadPosition;
+		return playbackHeadPosition - native_getPlaybackHeadPosition();
 	}
 
+	private native int native_getPlaybackHeadPosition();
 	public native void native_play();
 	public native void native_pause();
 	private native int native_write(byte[] audioData, int offsetInBytes, int sizeInBytes);