Decouple capture timestamp and reference time

media/capture/video/linux/v4l2_capture_delegate.cc

 // Copyright 2015 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.
 
 #include "media/capture/video/linux/v4l2_capture_delegate.h"
 
 #include <poll.h>
 #include <sys/fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ skipping 372 matching lines @@
     FillV4L2Buffer(&buffer, 0);
 
     if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_DQBUF, &buffer)) < 0) {
       SetErrorState(FROM_HERE, "Failed to dequeue capture buffer");
       return;
     }
 
     buffer_tracker_pool_[buffer.index]->set_payload_size(buffer.bytesused);
     const scoped_refptr<BufferTracker>& buffer_tracker =
         buffer_tracker_pool_[buffer.index];
+    base::TimeTicks now = base::TimeTicks::Now();
+    if (first_ref_time_.is_null())
+      first_ref_time_ = now;

[miu, 2016/05/18 22:35:40]

The |buffer| has a |timestamp| field you can translate:

  base::TimeDelta timestamp =
      base::TimeDelta::FromSeconds(buffer.timestamp.tv_sec) +
      base::TimeDelta::FromMicroseconds(buffer.timestamp.tv_usec);

...so you don't need the |first_ref_time_| mechanism here. :)

[qiangchen, 2016/05/20 17:55:14]

Done.

     client_->OnIncomingCapturedData(
         buffer_tracker->start(), buffer_tracker->payload_size(),
-        capture_format_, rotation_, base::TimeTicks::Now());
+        capture_format_, rotation_, now, now - first_ref_time_);
 
     if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0) {
       SetErrorState(FROM_HERE, "Failed to enqueue capture buffer");
       return;
     }
   }
 
   v4l2_task_runner_->PostTask(
       FROM_HERE, base::Bind(&V4L2CaptureDelegate::DoCapture, this));
 }
@@ skipping 25 matching lines @@
     DLOG(ERROR) << "Error mmap()ing a V4L2 buffer into userspace";
     return false;
   }
   start_ = static_cast<uint8_t*>(start);
   length_ = buffer.length;
   payload_size_ = 0;
   return true;
 }
 
 }  // namespace media