Use video source timestamp instead of system clock.

mediapipe/examples/ios/common/CommonViewController.h

@@ -18,6 +18,7 @@
 #import "mediapipe/objc/MPPGraph.h"
 #import "mediapipe/objc/MPPLayerRenderer.h"
 #import "mediapipe/objc/MPPPlayerInputSource.h"
+#import "mediapipe/objc/MPPTimestampConverter.h"
 
 typedef NS_ENUM(NSInteger, MediaPipeDemoSourceMode) {
   MediaPipeDemoSourceCamera,
@@ -60,4 +61,7 @@ typedef NS_ENUM(NSInteger, MediaPipeDemoSourceMode) {
 // Graph output stream.
 @property(nonatomic) const char* graphOutputStream;
 
+// Convert video time to mediapipe internal Timestamp
+@property(nonatomic) MPPTimestampConverter* timestampConverter;
+
 @end

mediapipe/examples/ios/common/CommonViewController.mm

@@ -76,6 +76,7 @@ static const char* kVideoQueueLabel = "com.google.mediapipe.example.videoQueue";
   self.renderer.layer.frame = self.liveView.layer.bounds;
   [self.liveView.layer addSublayer:self.renderer.layer];
   self.renderer.frameScaleMode = MPPFrameScaleModeFillAndCrop;
+  self.timestampConverter = [[MPPTimestampConverter alloc] init];
 
   dispatch_queue_attr_t qosAttribute = dispatch_queue_attr_make_with_qos_class(
       DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INTERACTIVE, /*relative_priority=*/0);
@@ -173,7 +174,8 @@ static const char* kVideoQueueLabel = "com.google.mediapipe.example.videoQueue";
 
   [self.mediapipeGraph sendPixelBuffer:imageBuffer
                             intoStream:self.graphInputStream
-                            packetType:MPPPacketTypePixelBuffer];
+                            packetType:MPPPacketTypePixelBuffer
+                            timestamp:[self.timestampConverter timestampForMediaTime:timestamp]];
 }
 
 #pragma mark - MPPGraphDelegate methods

mediapipe/objc/MPPGraph.mm

@@ -45,6 +45,8 @@
 
   /// Number of frames currently being processed by the graph.
   std::atomic<int32_t> _framesInFlight;
+  /// Used as a sequential timestamp for MediaPipe.
+  mediapipe::Timestamp _frameTimestamp;
   int64 _frameNumber;
 
   // Graph config modified to expose requested output streams.
@@ -367,16 +369,21 @@ void CallFrameDelegate(void* wrapperVoid, const std::string& streamName,
                      timestamp:timestamp
                 allowOverwrite:NO];
 }
+
 - (BOOL)sendPixelBuffer:(CVPixelBufferRef)imageBuffer
              intoStream:(const std::string&)inputName
              packetType:(MPPPacketType)packetType {
-  uint64_t us = std::chrono::duration_cast<std::chrono::microseconds>(std::chrono::high_resolution_clock::
-                                                                      now().time_since_epoch()).count();
+  _GTMDevAssert(_frameTimestamp < mediapipe::Timestamp::Done(),
+                @"Trying to send frame after stream is done.");
+  if (_frameTimestamp < mediapipe::Timestamp::Min()) {
+    _frameTimestamp = mediapipe::Timestamp::Min();
+  } else {
+    _frameTimestamp++;
+  }
   return [self sendPixelBuffer:imageBuffer
                     intoStream:inputName
                     packetType:packetType
-                     timestamp:mediapipe::Timestamp(us)];
-
+                     timestamp:_frameTimestamp];
 }
 
 - (void)debugPrintGlInfo {