AudioTrack lag: obtainBuffer timed out
- by BTR
I'm playing WAVs on my Android phone by loading the file and feeding the bytes into AudioTrack.write() via the FileInputStream BufferedInputStream DataInputStream method. The audio plays fine and when it is, I can easily adjust sample rate, volume, etc on the fly with nice performance. However, it's taking about two full seconds for a track to start playing. I know AudioTrack has an inescapable delay, but this is ridiculous. Every time I play a track, I get this:
03-13 14:55:57.100: WARN/AudioTrack(3454): obtainBuffer timed out (is the CPU pegged?) 0x2e9348 user=00000960, server=00000000
03-13 14:55:57.340: WARN/AudioFlinger(72): write blocked for 233 msecs, 9 delayed writes, thread 0xba28
I've noticed that the delayed write count increases by one every time I play a track -- even across multiple sessions -- from the time the phone has been turned on. The block time is always 230 - 240ms, which makes sense considering a minimum buffer size of 9600 on this device (9600 / 44100). I've seen this message in countless searches on the Internet, but it usually seems to be related to not playing audio at all or skipping audio. In my case, it's just a delayed start.
I'm running all my code in a high priority thread. Here's a truncated-yet-functional version of what I'm doing. This is the thread callback in my playback class. Again, this works (only playing 16-bit, 44.1kHz, stereo files right now), it just takes forever to start and has that obtainBuffer/delayed write message every time.
public void run()
{
// Load file
FileInputStream mFileInputStream;
try
{
// mFile is instance of custom file class -- this is correct,
// so don't sweat this line
mFileInputStream = new FileInputStream(mFile.path());
} catch (FileNotFoundException e) {}
BufferedInputStream mBufferedInputStream = new BufferedInputStream(mFileInputStream, mBufferLength);
DataInputStream mDataInputStream = new DataInputStream(mBufferedInputStream);
// Skip header
try
{
if (mDataInputStream.available() > 44)
mDataInputStream.skipBytes(44);
} catch (IOException e) {}
// Initialize device
mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, ConfigManager.SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT, ConfigManager.AUDIO_BUFFER_LENGTH,
AudioTrack.MODE_STREAM);
mAudioTrack.play();
// Initialize buffer
byte[] mByteArray = new byte[mBufferLength];
int mBytesToWrite = 0;
int mBytesWritten = 0;
// Loop to keep thread running
while (mRun)
{
// This flag is turned on when the user presses "play"
while (mPlaying)
{
try
{
// Check if data is available
if (mDataInputStream.available() > 0)
{
// Read data from file and write to audio device
mBytesToWrite = mDataInputStream.read(mByteArray, 0, mBufferLength);
mBytesWritten += mAudioTrack.write(mByteArray, 0, mBytesToWrite);
}
}
catch (IOException e)
{
}
}
}
}
If I can get past the artificially long lag, I can easily deal with the inherit latency by starting my write at a later, predictable position (ie, skip past the minimum buffer length when I start playing a file).
