OMXCameraAdapter: Update timstamp calculation and comment

In timestamp calculation, latency incurred in Ducati camera buffer
reaching CameraHal should be considered

Patchset 2:
 - Updated variable name, migrated to header file
 - Update comment description

Change-Id: Icc93c27a66477867e9c415b139a331646eb2fba8
Signed-off-by: Devaraj Rangasamy <dev@ti.com>

2 files changed, 10 insertions, 7 deletions

diff --git a/camera/OMXCameraAdapter/OMXCameraAdapter.cpp b/camera/OMXCameraAdapter/OMXCameraAdapter.cpp
index 2c1af45..3e94d1d 100644
--- a/camera/OMXCameraAdapter/OMXCameraAdapter.cpp
+++ b/camera/OMXCameraAdapter/OMXCameraAdapter.cpp
@@ -3149,16 +3149,17 @@ status_t OMXCameraAdapter::initCameraFrame( CameraFrame &frame,
     frame.mWidth = port->mWidth;
     frame.mHeight = port->mHeight;
 
-    // Calculating the time source delta of Ducati & system time only once at the start of camera.
-    // It's seen that there is a one-time constant diff between the ducati source clock &
-    // System monotonic timer, although both derived from the same 32KHz clock.
-    // This delta is offsetted to/from ducati timestamp to match with system time so that
-    // video timestamps are aligned with Audio with a periodic timestamp intervals.
-    // Do timeset offset calculation only when recording is in progress, when nTimestamp
-    // will be populated by Camera
+    // Timestamp in pBuffHeader->nTimeStamp is derived on DUCATI side, which is
+    // is not  same time value as derived using systemTime. It would be ideal to use
+    // exactly same time source across Android and Ducati, which is limited by
+    // system now. So, workaround for now is to find the time offset between the two
+    // time sources and compensate the difference, along with the latency involved
+    // in camera buffer reaching CameraHal. Also, Do timeset offset calculation only
+    // when recording is in progress, when nTimestamp will be populated by Camera
     if ( onlyOnce && mRecording )
         {
         mTimeSourceDelta = (pBuffHeader->nTimeStamp * 1000) - systemTime(SYSTEM_TIME_MONOTONIC);
+        mTimeSourceDelta += kCameraBufferLatencyNs;
         onlyOnce = false;
         }
 
diff --git a/camera/inc/OMXCameraAdapter/OMXCameraAdapter.h b/camera/inc/OMXCameraAdapter/OMXCameraAdapter.h
index 2a6ffc2..0cdd4bb 100644
--- a/camera/inc/OMXCameraAdapter/OMXCameraAdapter.h
+++ b/camera/inc/OMXCameraAdapter/OMXCameraAdapter.h
@@ -137,6 +137,8 @@ namespace android {
     }                                                                           \
 }
 
+const int64_t kCameraBufferLatencyNs = 250000000LL; // 250 ms
+
 ///OMX Specific Functions
 static OMX_ERRORTYPE OMXCameraAdapterEventHandler(OMX_IN OMX_HANDLETYPE hComponent,
                                         OMX_IN OMX_PTR pAppData,