Add helper to calculate frame dependencies based on encoder buffer usage

Bug: webrtc:10342
Change-Id: I1d856d060c2defcd10310f0d8639ce8a9554fff3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168194
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30458}

modules/video_coding/frame_dependencies_calculator.h

@@ -0,0 +1,53 @@
+/*
+ *  Copyright (c) 2020 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 MODULES_VIDEO_CODING_FRAME_DEPENDENCIES_CALCULATOR_H_
+#define MODULES_VIDEO_CODING_FRAME_DEPENDENCIES_CALCULATOR_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/types/optional.h"
+#include "api/array_view.h"
+#include "api/video/video_frame_type.h"
+#include "common_video/generic_frame_descriptor/generic_frame_info.h"
+#include "rtc_base/synchronization/sequence_checker.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace webrtc {
+
+class FrameDependenciesCalculator {
+ public:
+  FrameDependenciesCalculator() = default;
+  FrameDependenciesCalculator(FrameDependenciesCalculator&&) = default;
+  FrameDependenciesCalculator& operator=(FrameDependenciesCalculator&&) =
+      default;
+
+  // Calculates frame dependencies based on previous encoder buffer usage.
+  absl::InlinedVector<int64_t, 5> FromBuffersUsage(
+      VideoFrameType frame_type,
+      int64_t frame_id,
+      rtc::ArrayView<const CodecBufferUsage> buffers_usage);
+
+ private:
+  struct BufferUsage {
+    absl::optional<int64_t> frame_id;
+    absl::InlinedVector<int64_t, 4> dependencies;
+  };
+
+  SequenceChecker checker_;
+  absl::InlinedVector<BufferUsage, 4> buffers_ RTC_GUARDED_BY(checker_);
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_VIDEO_CODING_FRAME_DEPENDENCIES_CALCULATOR_H_