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

media/capture/video/mac/video_capture_device_avfoundation_mac.mm

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "media/capture/video/mac/video_capture_device_avfoundation_mac.h"
 
 #import <CoreVideo/CoreVideo.h>
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
@@ skipping 310 matching lines @@
       baseAddress = static_cast<char*>(CVPixelBufferGetBaseAddress(videoFrame));
       frameSize = CVPixelBufferGetHeight(videoFrame) *
                   CVPixelBufferGetBytesPerRow(videoFrame);
     } else {
       videoFrame = nil;
     }
   }
 
   {
     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);
     }
   }
 
   if (videoFrame)
     CVPixelBufferUnlockBaseAddress(videoFrame, kCVPixelBufferLock_ReadOnly);
 }
 
 - (void)onVideoError:(NSNotification*)errorNotification {
   NSError* error = base::mac::ObjCCast<NSError>([[errorNotification userInfo]
       objectForKey:AVFoundationGlue::AVCaptureSessionErrorKey()]);
   [self sendErrorString:[NSString
                             stringWithFormat:@"%@: %@",
                                              [error localizedDescription],
                                              [error localizedFailureReason]]];
 }
 
 - (void)sendErrorString:(NSString*)error {
   DLOG(ERROR) << [error UTF8String];
   base::AutoLock lock(lock_);
   if (frameReceiver_)
     frameReceiver_->ReceiveError([error UTF8String]);
 }
 
 @end