1 files changed, 148 insertions, 0 deletions
diff --git a/webrtc/modules/video_processing/video_decimator.cc b/webrtc/modules/video_processing/video_decimator.cc
new file mode 100644
index 0000000000..63e347b026
--- /dev/null
+++ b/webrtc/modules/video_processing/video_decimator.cc
@@ -0,0 +1,148 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/video_processing/include/video_processing.h"
+#include "webrtc/modules/video_processing/video_decimator.h"
+#include "webrtc/system_wrappers/include/tick_util.h"
+
+#define VD_MIN(a, b) ((a) < (b)) ? (a) : (b)
+
+namespace webrtc {
+
+VPMVideoDecimator::VPMVideoDecimator() {
+  Reset();
+}
+
+VPMVideoDecimator::~VPMVideoDecimator() {}
+
+void VPMVideoDecimator::Reset() {
+  overshoot_modifier_ = 0;
+  drop_count_ = 0;
+  keep_count_ = 0;
+  target_frame_rate_ = 30;
+  incoming_frame_rate_ = 0.0f;
+  memset(incoming_frame_times_, 0, sizeof(incoming_frame_times_));
+  enable_temporal_decimation_ = true;
+}
+
+void VPMVideoDecimator::EnableTemporalDecimation(bool enable) {
+  enable_temporal_decimation_ = enable;
+}
+
+void VPMVideoDecimator::SetTargetFramerate(int frame_rate) {
+  RTC_DCHECK(frame_rate);
+  target_frame_rate_ = frame_rate;
+}
+
+bool VPMVideoDecimator::DropFrame() {
+  if (!enable_temporal_decimation_)
+    return false;
+
+  if (incoming_frame_rate_ <= 0)
+    return false;
+
+  const uint32_t incomingframe_rate =
+      static_cast<uint32_t>(incoming_frame_rate_ + 0.5f);
+
+  if (target_frame_rate_ == 0)
+    return true;
+
+  bool drop = false;
+  if (incomingframe_rate > target_frame_rate_) {
+    int32_t overshoot =
+        overshoot_modifier_ + (incomingframe_rate - target_frame_rate_);
+    if (overshoot < 0) {
+      overshoot = 0;
+      overshoot_modifier_ = 0;
+    }
+
+    if (overshoot && 2 * overshoot < (int32_t)incomingframe_rate) {
+      if (drop_count_) {  // Just got here so drop to be sure.
+        drop_count_ = 0;
+        return true;
+      }
+      const uint32_t dropVar = incomingframe_rate / overshoot;
+
+      if (keep_count_ >= dropVar) {
+        drop = true;
+        overshoot_modifier_ = -((int32_t)incomingframe_rate % overshoot) / 3;
+        keep_count_ = 1;
+      } else {
+        keep_count_++;
+      }
+    } else {
+      keep_count_ = 0;
+      const uint32_t dropVar = overshoot / target_frame_rate_;
+      if (drop_count_ < dropVar) {
+        drop = true;
+        drop_count_++;
+      } else {
+        overshoot_modifier_ = overshoot % target_frame_rate_;
+        drop = false;
+        drop_count_ = 0;
+      }
+    }
+  }
+  return drop;
+}
+
+uint32_t VPMVideoDecimator::GetDecimatedFrameRate() {
+  ProcessIncomingframe_rate(TickTime::MillisecondTimestamp());
+  if (!enable_temporal_decimation_) {
+    return static_cast<uint32_t>(incoming_frame_rate_ + 0.5f);
+  }
+  return VD_MIN(target_frame_rate_,
+                static_cast<uint32_t>(incoming_frame_rate_ + 0.5f));
+}
+
+uint32_t VPMVideoDecimator::Inputframe_rate() {
+  ProcessIncomingframe_rate(TickTime::MillisecondTimestamp());
+  return static_cast<uint32_t>(incoming_frame_rate_ + 0.5f);
+}
+
+void VPMVideoDecimator::UpdateIncomingframe_rate() {
+  int64_t now = TickTime::MillisecondTimestamp();
+  if (incoming_frame_times_[0] == 0) {
+    // First no shift.
+  } else {
+    // Shift.
+    for (int i = kFrameCountHistory_size - 2; i >= 0; i--) {
+      incoming_frame_times_[i + 1] = incoming_frame_times_[i];
+    }
+  }
+  incoming_frame_times_[0] = now;
+  ProcessIncomingframe_rate(now);
+}
+
+void VPMVideoDecimator::ProcessIncomingframe_rate(int64_t now) {
+  int32_t num = 0;
+  int32_t nrOfFrames = 0;
+  for (num = 1; num < (kFrameCountHistory_size - 1); num++) {
+    // Don't use data older than 2sec.
+    if (incoming_frame_times_[num] <= 0 ||
+        now - incoming_frame_times_[num] > kFrameHistoryWindowMs) {
+      break;
+    } else {
+      nrOfFrames++;
+    }
+  }
+  if (num > 1) {
+    int64_t diff = now - incoming_frame_times_[num - 1];
+    incoming_frame_rate_ = 1.0;
+    if (diff > 0) {
+      incoming_frame_rate_ = nrOfFrames * 1000.0f / static_cast<float>(diff);
+    }
+  } else {
+    incoming_frame_rate_ = static_cast<float>(nrOfFrames);
+  }
+}
+
+}  // namespace webrtc