/**
* As long as the processing thread is active, this executes detection on frames continuously.
* The next pending frame is either immediately available or hasn't been received yet. Once it
* is available, we transfer the frame info to local variables and run detection on that frame.
* It immediately loops back for the next frame without pausing.
*
* <p>If detection takes longer than the time in between new frames from the camera, this will
* mean that this loop will run without ever waiting on a frame, avoiding any context switching
* or frame acquisition time latency.
*
* <p>If you find that this is using more CPU than you'd like, you should probably decrease the
* FPS setting above to allow for some idle time in between frames.
*/
@Override
public void run() {
Frame outputFrame;
ByteBuffer data;
while (true) {
synchronized (mLock) {
if (mActive && (mPendingFrameData == null)) {
try {
// Wait for the next frame to be received from the camera, since we
// don't have it yet.
mLock.wait();
} catch (InterruptedException e) {
Log.d(TAG, mContext.getString(R.string.frame_processing_loop_terminated), e);
return;
}
}
if (!mActive) {
// Exit the loop once this camera source is stopped or released. We check
// this here, immediately after the wait() above, to handle the case where
// setActive(false) had been called, triggering the termination of this
// loop.
return;
}
outputFrame =
new Frame.Builder()
.setImageData(
mPendingFrameData,
mPreviewSize.getWidth(),
mPreviewSize.getHeight(),
ImageFormat.NV21)
.setId(mPendingFrameId)
.setTimestampMillis(mPendingTimeMillis)
.setRotation(mRotation)
.build();
// Hold onto the frame data locally, so that we can use this for detection
// below. We need to clear mPendingFrameData to ensure that this buffer isn't
// recycled back to the camera before we are done using that data.
data = mPendingFrameData;
mPendingFrameData = null;
}
// The code below needs to run outside of synchronization, because this will allow
// the camera to add pending frame(s) while we are running detection on the current
// frame.
try {
mDetector.receiveFrame(outputFrame);
} catch (Throwable t) {
Log.e(TAG, mContext.getString(R.string.exception_from_receiver), t);
} finally {
mCamera.addCallbackBuffer(data.array());
}
}
}
/**
* Releases the underlying receiver. This is only safe to do after the associated thread has
* completed, which is managed in camera source's release method above.
*/
@SuppressLint("Assert")
void release() {
assert (mProcessingThread.getState() == State.TERMINATED);
mDetector.release();
mDetector = null;
}