I have an app that plays an mp3 file and I'm trying to update a custom field in synchrony with certain times we have tabulated for the sound playback (kind of like a karaoke effect). I'm using a Handler to schedule these updates. In my custom field class, I define a Runnable that is supposed to run the update at the right time:
private final Runnable mTrigger = new Runnable() {
#Override
public void run() {
int now = mPlayer.getCurrentPosition();
if (mState == STATE_PLAYING && mUpdateAction != null) {
if (mTriggerTime - now > MAX_PREMATURE_TRIGGER) {
// Sound is lagging too much; reschedule this trigger
mHandler.postDelayed(this, mTriggerTime - now);
} else {
// Run the update
mUpdateAction.run();
}
}
}
};
When I call mPlayer.start() I schedule the first update by calling mHandler.postDelayed(mTrigger, timeToFirstUpdate). Each update action decides what the next update will be and schedules it (by calling mHandler.postDelayed(mTrigger, timeToNextUpdate)). The updates times are typically a few hundred milliseconds apart.
The problem is that, while some updates are happening promptly at the scheduled times, others can be delayed by 200 milliseconds or more, which is quite noticeable to the user. I'm not doing anything in my app between these updates other than playing the sound. (No background worker threads; no other display updates.) The delays appear to be random and vary considerably each time through.
I didn't think that the timing for postDelayed would be this imprecise! I don't know if this is an emulator issue or a problem with my approach. Does sound playback screw up the timing of the UI thread loop? Should I move the timing into a background thread (and is it safe to call mPlayer.getCurrentPosition() from a background thread)? Something else?
After much experimenting, it seems like the problem is the emulator. When I ran everything on a speedier workstation, the problem seems to have gone away.
Related
I want to make 8 squares change colors between red/black periodically.
I acomplish this using timer.schedule with period time in milliseconds and it work
BUT then I realized that I need to use small time between this transitions (example nanoseconds).
To accomplish that I wrote this code:
timerTask = new TimerTask() {
public void run() {
handler.post(new Runnable() {
public void run(){
//CODE OF THE TASK.
}
});
}
};
//To make schedule this task in 5 nanoseconds I use this!
exec = new ScheduledThreadPoolExecutor(1);
exec.scheduleAtFixedRate(timerTask, 0, 5, TimeUnit.NANOSECONDS);
But when I run this, the UI is not updating (seems to be stuck), but in logcat, all the logs are printing very fast. How can I achieve to make a task periodically x nanoseconds?
The entire Android UI runs at 60Hz- 60 updates per second. This means the minimum time between redraws is 16 ms. You cannot run it at a higher framerate. Nor are human eyes capable of seeing changes at a much higher frequency than that.
iOS and most video game consoles also work on a 60 Hz refresh rate. You'd find very few to no systems that go faster.
I'm not sure what exactly you're trying to accomplish, but I'm fairly certain you're trying to do it the wrong way.
ALSO: I notice your timer task posts to a handler. That means your timer task is going to tell the main thread to run something, and the timer task is running in nanoseconds. YOu're basically going to choke your main thread full of "run this task" messages, then eventually crash with an OOM error when the event queue becomes so massive it can't add any more (which may take several minutes), because there's no way you're processing them fast enough with the thread switching overhead.
After doing a lot of research, I realized that in order to get the view to refresh so quickly, I needed the use of SurfaceView and a Thread to make the UI redraw very fast, I really had no knowledge of this. Thanks for the help
Hey I am currently designing an app where some code gets executed every 200ms. The thread I use for this looks like this (simplified):
final Handler handler = new Handler();
Runnable runnable = new Runnable()
{ public void run()
{
handler.postDelayed(this, 200);
switch (status){
case 1: check(1);p2.setBackgroundColor(0x00000000); p1.setBackgroundColor(0xDDCC0000); status = 2; break;
case 2: check(2);p1.setBackgroundColor(0x00000000); p2.setBackgroundColor(0xAAAA0000); status = 1; break;
}
}
}; runnable.run();
check() contains some non-UI code lines.
The problem is, that the postDelayed-200-ms start, when the queue is fully executed and not at the beginning so all time that the system needs to execute the commands stacks and stacks all the time so these are actually ~210-230ms (depending on CPU load)
Then I tried to get the system date at the beginning of the thread and add 200ms to it but this results in some other, "heavier" errors.
I have no problem with more than 200ms delay, I just want to get it running stable.
I hope you understand my problem and can give some advice to me.
EDIT: I know got to know that the Handler runs acceptable (delay of 4ms on 200ms). The problem are the methods I am calling then. I will open a new question
If check() contains non-ui code lines then you should run those in a separate thread.
The bottom line is that the UI thread is *really busy, so, you can ask it to do something every 200ms but you aren't guaranteed any precision since the Device is doing its best to do all sorts of other things. When you say "heavier problems" what do you mean exactly?
I would try to start a Thread and just Log every 200ms to see if the device is willing to accurately do *anything at the rate you wish. If it does, then you can send messages to the UI thread to draw and if you find that its the drawing that is delayed, then perhaps you need to reduce your delay to give the UI thread time to finish drawing? (obviously this is also highly imprecise and will vary wildly from device to device).
Did you try doing it using Timers? A basic implementation would look like
new Timer().scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
// TODO Auto-generated method stub
}
}, 200, 200);
You can try using the alarm service as well. that should give you accurate (or at least consistent) results.
Apparently no exception is thrown so that I can recognize an error while buffering streaming audio content. For example I've disconnected my router and the app will continue to try to buffer the whole time. When I reconnect then it completes buffering and continues even after being disconnected for over a minute!
So the problem is I can't let my user sit there for that long without considering that a problem. What is the proper method to detect a buffering problem with the Android media player?
I'm thinking about using a Timer for a timeout. I'll start probably with 15 seconds (using a proxy I tested a 5kbps connection, which would be a worst case, was able to start playing in 6-10 seconds, so I think 15 seconds would be a reasonable timeout period). Does this sound like a good plan? If so should I create a new Timer with each buffer attempt or should I keep the same Timer throughout the lifetime of the playback service?
So basically I'm asking two questions:
1) What's the proper way to detect if a buffer is having a problem? Is there a listener I'm overlooking? I've tried MediaPlayer.OnErrorListener of course that doesn't fire in my tests. My conclusion is I have to have a timeout to detect a buffering error.
2) If I'm correct on number one, what is the proper way to use a Timer? Create one with each buffer attempt or reuse the same one? EDIT Also should I restart the (or cancel and create a new) Timer onBufferUpdate? With the onBufferUpdate listener I should know that some data is coming back so should maybe reset the timer with that.
From your question, I understand that the primary objective is to detect a situation if your player is stalled due to buffering and take some actions thereof. To handle this situation, I feel that the following 2 listeners may be helpful to identify the same.
MediaPlayer.onBufferingUpdate would provide the timely progress of the buffering. So, if there are 2 callbacks with same percent value, this could be an indication of potential buffering.
There is another listener MediaPlayer.onInfoListener which has some specific events which could be of interest to you. On this listener, if the what is MEDIA_INFO_BUFFERING_START, this would indicate that the player is pausing the playback for buffering i.e. trigger for your logic. Similarly MEDIA_INFO_BUFFERING_END indicates the restart of the playback after filling the buffers.
You Should see this article. The mediaplayer has a ErrorListener to get any error.
http://developer.android.com/reference/android/media/MediaPlayer.OnErrorListener.html
int count=40;//for 40 seconds to wait for buffering after it will finish the activity
//boolean timeoutflag=false;
timeout = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
System.out.println("value of count="+msg.getData().getLong("count"));
if (msg.getData().getBoolean("valid")) {
if (msg.getData().getLong("count") == 0 && !timeoutflag)
{
if (pDialog != null && pDialog.isShowing())
{
try
{
pDialog.dismiss();
}catch(Exception e)
{
e.printStackTrace();
}
}
Toast.makeText(getApplicationContext(),
"Unable To Load This Video", Toast.LENGTH_LONG).show();
finish();
} else {
}
}
}
};
timeout.postDelayed(null, 0);
new Thread(new Runnable() {
#Override
public void run() {
while (count > 0) {
try {
Thread.sleep(1020);
} catch (Exception e) {
}
Message msg = new Message();
Bundle b = new Bundle();
b.putBoolean("valid", true);
b.putLong("count", --count);
msg.setData(b);
timeout.sendMessage(msg);
}
}
}).start();
// set timeoutflag=true; in setOnPreparedListener of video view
For buffering during preparation, you have to set your own timer which calls player.reset() after some interval. This puts the player back into init state.
For buffering after preparation (during play) you have to monitor getPosition(). If it falls behind some maximum, call reset(). This allows you to set an experience threshold for your playback. Handles not only failed connection, but also choppy connection.
Best solution is to not use MediaPlayer. Use a public VLC derivative instead. MP has too many internalized private design limitations requiring horrible workarounds (eg. CANT add codecs). RTFM gives you false hope in this case.
Unless you are doing a very straight laced android app, don't depend on any android api. Some opensource substitutes are better supported, and for good reason.
(really bandeely olly jolly satisfying editorial rant deleted)
I have a problem with this code used for Android (Java)
handler.postDelayed(new Runnable(){
public void run(){
// Your code goes here...
}
}, 500);
If the delay is about 500ms then the program seems to repeat the task at 0.5s, but if I change to less than 100ms or even less it does not follow any more. I test the brightness change and for a while it can repeat the change of brightness at that rate, but then slow down and come back to normal flash rate again. It seems unstable. Do you have any code that give exact delay regardless of the load of the phone's CPU.
Many thanks
Not from Java, no; stock Java isn't a real-time system.
Timing precision is subject to the whims of the JVM and the OS's scheduler. You may be able to get incrementally more precise, but there's no guarantee of the kind of precision you're looking for.
You might be able to do something more precise if you use a CountDownTimer which has a periodic tick. Essentially you set it to count down for a period which can be hours if need be, and there are two methods one method is called on each tick, and the other at the end of the timer at which point you could start another one. Anyway you could set the tick to be very fast, and then only kick off the code at the delay point by check the actual time difference in the click. I think thats about the best you could do. Essentially inside the tick you would issue a signal if the right amout of time had actually passed. That signal would either kick off the thread or release something the already running thread was waiting on. What is the value of the CountDownTimer, I guess its just that you can do a very frequent polling, and elapsed time check. Although its not guaranteed, the time between the ticks you can set it to a high frequency and check/poll very frequently. This could lead to a smooth performance not unlike a realtime system. Its more likely to be accurate because its just issuing a signal and not taking up the resources of threading just to issue the signal. You might also try an IntentService to perform the tasks and just call startService(intentToIntentService) each call. See if the threading works better inside a service like IntentService which does queue them up I believe.
Date startDate = new Date();
long startTime = startDate.getTime();
// Tick called every 10th of a second. OnFinish called at Signal.
CountDownTimer ctDownTimer = new CountDownTimer(30000, 100) {
long startIntervalTime=startTime;
public void onTick(long millisUntilFinished) {
Date now = new Date();
long nowTime = now.getTime();
if ((startIntervalTime - nowTime) > 100)
{
issueSignal();
intervalStartTime=nowTime;
}
now=null;
}
public void onFinish() {
Log.d("MyClass", "Done") // Maybe start out.
}
}.start();
I have a simple, classic, statement that every 200 milliseconds plays a sound (a metronome).
I wrote it using Handlers, and then in another way, using Threads.
The problem is the same in both ways: when I press hardware home button, or also simply when I press a button to open a ListView, the metronome terribly slowdown for a while.
This problem (not so strong, but however present) presents also doing nothing and leaving the application in foreground.
Any ideas?
Here's the code:
public class Metronome implements Runnable{
private Handler mHandler = new Handler();
public static long mStartTime;
Main mainContext;
public Metronomo(Main context) {
mainContext = context;
}
public void play() {
mStartTime = System.currentTimeMillis();
mHandler.postDelayed(this, 100);
}
public final void stop(){
mHandler.removeCallbacks(this);
}
public void run(){
//play the ogg file in position 1
mSoundManager.playSound(1);
//reschedule the next playing after 200ms
mHandler.postAtTime(this, SystemClock.uptimeMillis() + 200);
}
};
Are you using some kind of pause statement to wait between beats? You could try basing the timing on multiples of a system clock value instead. That way you may still get beats that occur late (or not at all) but you wouldn't get a slow down. Hope that makes some kind of sense.
This is more of a comment but I don't have enough rep to leave comments just yet.
My phone seems to be able to play midi files, which are a pretty compact way to represent sound, perhaps you could dynamically create one and use that for the metronome? I'm assuming that the synthesis is handled at a lower level than would ordinarily be accessible to you so that the timing would be better, but I don't know that for a fact.
When this play sound is called
mSoundManager.playSound(1);
Android waits until that call is finished, then you call
mHandler.postAtTime(this, SystemClock.uptimeMillis() + 200);
however, if you reverse those calls, you may find that the timing is more accurate.
mHandler.postAtTime(this, SystemClock.uptimeMillis() + 200);
mSoundManager.playSound(1);
You can't count on your sound taking exactly the same amount of time to play, so telling the handler to post first is a bit better. Still not ideal, however.
Another consideration is that you're re-computing uptime and adding some more time to that (200 in this case). Why not use the modulus operator on your uptime, to ensure that your next requested post time is more precisely scheduled?
long divisions = SystemClock.uptimeMillis() % 200; // precisely scheduled event timings since system boot.
long nextDivision = divisions + 1; // the next desired event timing
mHandler.postAtTime(this, nextDivision * 200); // scaled back up to number of milli seconds
// now do more heavy lifting that would otherwise have affected uptimeMillis call
mSoundManager.playSound(1);