Extract simulcast rate allocation outside of video encoder.

webrtc/modules/video_coding/utility/simulcast_rate_allocator.h

+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#ifndef WEBRTC_MODULES_VIDEO_CODING_UTILITY_SIMULCAST_RATE_ALLOCATOR_H_
+#define WEBRTC_MODULES_VIDEO_CODING_UTILITY_SIMULCAST_RATE_ALLOCATOR_H_
+
+#include <vector>
+
+#include "webrtc/base/basictypes.h"
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/video_encoder.h"
+
+namespace webrtc {
+
+class SimulcastRateAllocator {
+ public:
+  explicit SimulcastRateAllocator(const VideoCodec& codec);
+
+  std::vector<uint32_t> GetAllocation(uint32_t bitrate_kbps) const;
+  const VideoCodec& GetCodec() const;
+
+ private:
+  const VideoCodec codec_;
+
+  RTC_DISALLOW_COPY_AND_ASSIGN(SimulcastRateAllocator);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_VIDEO_CODING_UTILITY_SIMULCAST_RATE_ALLOCATOR_H_