How do I handle calls to AudioTrack from jni without crashing?
- by icecream
I was trying to write to an AudioTrack from a jni callback, and I get a signal 7 (SIGBUS), fault addr 00000000.
I have looked at the Wolf3D example for odroid and they seem to use a android.os.Handler to post a Runnable that will do an update in the correct thread context. I have also tried AttachCurrentThread, but I fail in this case also.
It works to play the sound when running from the constructor even if I wrap it in a thread and then post it to the handler. When I do the "same" via a callback from jni it fails. I assume I am braeaking some rules, but I haven't been able to figure out what they are. So far, I haven't found the answer here on SO.
So I wonder if anyone knows how this should be done.
EDIT: Answered below.
The following code is to illustrate the problem.
Java:
package com.example.jniaudiotrack;
import android.app.Activity;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
public class JniAudioTrackActivity extends Activity {
AudioTrack mAudioTrack;
byte[] mArr;
public static final Handler mHandler = new Handler();
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mArr = new byte[2048];
for (int i = 0; i < 2048; i++) {
mArr[i] = (byte) (Math.sin(i) * 128);
}
mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
11025,
AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_8BIT,
2048,
AudioTrack.MODE_STREAM);
mAudioTrack.play();
new Thread(new Runnable() {
public void run() {
mHandler.post(new Runnable() {
public void run() {
mAudioTrack.write(mArr, 0, 2048);
Log.i(TAG, "*** Handler from constructor ***");
}
});
}
}).start();
new Thread(new Runnable() {
public void run() {
audioFunc();
}
}).start();
}
public native void audioFunc();
@SuppressWarnings("unused")
private void audioCB() {
mHandler.post(new Runnable() {
public void run() {
mAudioTrack.write(mArr, 0, 2048);
Log.i(TAG, "*** audioCB called ***");
}
});
}
private static final String TAG = "JniAudioTrackActivity";
static {
System.loadLibrary("jni_audiotrack");
}
}
cpp:
#include <jni.h>
extern "C" {
JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj);
}
JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj)
{
JNIEnv* jniEnv;
JavaVM* vm;
env->GetJavaVM(&vm);
vm->AttachCurrentThread(&jniEnv, 0);
jclass cls = env->GetObjectClass(obj);
jmethodID audioCBID = env->GetMethodID(cls, "audioCB", "()V");
if (!audioCBID) {
return;
}
env->CallVoidMethod(cls, audioCBID);
}
Trace snippet:
I/DEBUG ( 1653): pid: 9811, tid: 9811 >>> com.example.jniaudiotrack <<<
I/DEBUG ( 1653): signal 7 (SIGBUS), fault addr 00000000
I/DEBUG ( 1653): r0 00000800 r1 00000026 r2 00000001 r3 00000000
I/DEBUG ( 1653): r4 42385726 r5 41049e54 r6 bee25570 r7 ad00e540
I/DEBUG ( 1653): r8 000040f8 r9 41048200 10 41049e44 fp 00000000
I/DEBUG ( 1653): ip 000000f8 sp bee25530 lr ad02dbb5 pc ad012358 cpsr 20000010
I/DEBUG ( 1653): #00 pc 00012358 /system/lib/libdvm.so
