Mac Video Capture: Sending the timestamps provided by the driver to the capture pipeline

media/capture/video/mac/video_capture_device_avfoundation_mac.mm

Index: media/capture/video/mac/video_capture_device_avfoundation_mac.mm
diff --git a/media/capture/video/mac/video_capture_device_avfoundation_mac.mm b/media/capture/video/mac/video_capture_device_avfoundation_mac.mm
index deb14080cfd2f2cb16709c9dd473df7cd809d2fd..beb196ac6d76706a94d0a97196ca467eb3970ebb 100644
--- a/media/capture/video/mac/video_capture_device_avfoundation_mac.mm
+++ b/media/capture/video/mac/video_capture_device_avfoundation_mac.mm
@@ -328,9 +328,16 @@ didOutputSampleBuffer:(CoreMediaGlue::CMSampleBufferRef)sampleBuffer
 
   {
     base::AutoLock lock(lock_);
+    const int microseconds_per_second = 1000000;

[mcasas, 2015/10/31 03:24:25]

Instead of |microseconds_per_second|, you should use
base::TimeBase::kMicrosecondsPerSecond| [1], here and
in the QTKit file.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/base/time/time.h&s...

[qiangchen, 2015/11/02 18:21:21]

Done.

+    CoreMediaGlue::CMTime cm_timestamp =
+        CoreMediaGlue::CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
+    const base::TimeTicks timestamp =

[mcasas, 2015/10/31 03:24:25]

At least DCHECK_NE(0, cm_timestamp.timescale);

[qiangchen, 2015/11/02 18:21:21]

Did a fallback code path in case the timestamp is invalid.

+        base::TimeTicks() + base::TimeDelta::FromMicroseconds(
+                                cm_timestamp.value * microseconds_per_second /
+                                cm_timestamp.timescale);
     if (frameReceiver_ && baseAddress) {
       frameReceiver_->ReceiveFrame(reinterpret_cast<uint8_t*>(baseAddress),
-                                   frameSize, captureFormat, 0, 0);
+                                   frameSize, captureFormat, 0, 0, timestamp);
     }
   }