java - Why this code have performance issue even without synchronized keyword? -

why following code have performance issue, frame camera not smooth.

public class videocaptureandroid implements previewcallback, callback{   private integer devicerotation = integer.max_value;    public videocaptureandroid(context context, int id, long native_capturer) {     devicerotationnotifier = new orientationeventlistener(context, sensormanager.sensor_delay_normal) {       public void onorientationchanged(int orientation) {         if (orientation == orientation_unknown) {           log.d(tag, "the device rotation angle unknown.");           return;         }          synchronized(devicerotation) {           if (devicerotation != orientation) {             devicerotation = orientation;           }         }       }     };      exchanger<handler> handlerexchanger = new exchanger<handler>();     camerathread = new camerathread(handlerexchanger);     camerathread.start();   }    public synchronized void onpreviewframe(byte[] data, camera callbackcamera) {      int framerotation = info.orientation;     if (info.facing == camera.camerainfo.camera_facing_front) {        framerotation = (info.orientation - devicerotation + 360) % 360;     } else if (info.facing == camera.camerainfo.camera_facing_back) {        framerotation = (info.orientation + devicerotation) % 360;     }     onframe(data, data.length, native_capturer, framerotation);     camera.addcallbackbuffer(data);   }    } 

seems if comment out following code, frame smooth, , no performance issues. didn't using synchronized in onpreviewframe access devicerotation, why impacted onorientationchanged?

if (info.facing == camera.camerainfo.camera_facing_front) {    framerotation = (info.orientation - devicerotation + 360) % 360; } else if (info.facing == camera.camerainfo.camera_facing_back) {    framerotation = (info.orientation + devicerotation) % 360; } 

the code have indicated not problem. modulo operations slow, doing single 1 each frame not going have huge impact. framerotation value being passed onframe() can assume applying matrix or other transform rotate data. expensive operation , involves use of 1 or more temporary buffers (or bitmap objects), uses heap , slow. i'm assuming info.orientation being passed unaltered onframe() result in no adjustment frame. hence, removal of 2 lines have indicated result in no heavy processing in onframe(), why jitter disappears.

you can track down better using traceview or systrace confirm.