Throttle video frame delivery when camera pumps it too fast on Android.

This allows JS to get desired frame rate when camera delivers frames too fast.

BUG=285394
R=qinmin@chromium.org

Review URL: https://codereview.chromium.org/23440037

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223702 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 27 insertions, 3 deletions

diff --git a/media/video/capture/android/video_capture_device_android.cc b/media/video/capture/android/video_capture_device_android.cc
index 152cfda..3574760 100644
--- a/media/video/capture/android/video_capture_device_android.cc
+++ b/media/video/capture/android/video_capture_device_android.cc
@@ -94,6 +94,7 @@ bool VideoCaptureDeviceAndroid::RegisterVideoCaptureDevice(JNIEnv* env) {
 
 VideoCaptureDeviceAndroid::VideoCaptureDeviceAndroid(const Name& device_name)
     : state_(kIdle),
+      got_first_frame_(false),
       observer_(NULL),
       device_name_(device_name),
       current_settings_() {
@@ -155,6 +156,12 @@ void VideoCaptureDeviceAndroid::Allocate(
   CHECK(current_settings_.width > 0 && !(current_settings_.width % 2));
   CHECK(current_settings_.height > 0 && !(current_settings_.height % 2));
 
+  if (capture_format.frame_rate > 0) {
+    frame_interval_ = base::TimeDelta::FromMicroseconds(
+        (base::Time::kMicrosecondsPerSecond + capture_format.frame_rate - 1) /
+        capture_format.frame_rate);
+  }
+
   DVLOG(1) << "VideoCaptureDeviceAndroid::Allocate: queried width="
            << current_settings_.width
            << ", height="
@@ -169,6 +176,7 @@ void VideoCaptureDeviceAndroid::Start() {
   DVLOG(1) << "VideoCaptureDeviceAndroid::Start";
   {
     base::AutoLock lock(lock_);
+    got_first_frame_ = false;
     DCHECK_EQ(state_, kAllocated);
   }
 
@@ -249,9 +257,21 @@ void VideoCaptureDeviceAndroid::OnFrameAvailable(
     return;
   }
 
-  observer_->OnIncomingCapturedFrame(
-      reinterpret_cast<uint8*>(buffer), length, base::Time::Now(),
-      rotation, flip_vert, flip_horiz);
+  base::TimeTicks current_time = base::TimeTicks::Now();
+  if (!got_first_frame_) {
+    // Set aside one frame allowance for fluctuation.
+    expected_next_frame_time_ = current_time - frame_interval_;
+    got_first_frame_ = true;
+  }
+
+  // Deliver the frame when it doesn't arrive too early.
+  if (expected_next_frame_time_ <= current_time) {
+    expected_next_frame_time_ += frame_interval_;
+
+    observer_->OnIncomingCapturedFrame(
+        reinterpret_cast<uint8*>(buffer), length, base::Time::Now(),
+        rotation, flip_vert, flip_horiz);
+  }
 
   env->ReleaseByteArrayElements(data, buffer, JNI_ABORT);
 }
diff --git a/media/video/capture/android/video_capture_device_android.h b/media/video/capture/android/video_capture_device_android.h
index 297a66d..845d278 100644
--- a/media/video/capture/android/video_capture_device_android.h
+++ b/media/video/capture/android/video_capture_device_android.h
@@ -11,6 +11,7 @@
 #include "base/android/scoped_java_ref.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread.h"
+#include "base/time/time.h"
 #include "media/base/media_export.h"
 #include "media/video/capture/video_capture_device.h"
 
@@ -61,6 +62,9 @@ class MEDIA_EXPORT VideoCaptureDeviceAndroid : public VideoCaptureDevice1 {
   // accessed from different threads.
   base::Lock lock_;
   InternalState state_;
+  bool got_first_frame_;
+  base::TimeTicks expected_next_frame_time_;
+  base::TimeDelta frame_interval_;
   VideoCaptureDevice::EventHandler* observer_;
 
   Name device_name_;