Implement |pic_order_cnt| computation for VTVideoDecode accelerator.

media/video/h264_poc.h

+// Copyright 2014 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.
+
+#ifndef MEDIA_VIDEO_H264_POC_H_
+#define MEDIA_VIDEO_H264_POC_H_
+
+namespace media {
+
+struct H264SPS;
+struct H264SliceHeader;
+
+class MEDIA_EXPORT H264POC {
+ public:
+  H264POC();
+  ~H264POC();
+
+  // Compute the picture order count for a slice, storing the result into
+  // |*pic_order_cnt|.
+  bool ComputePicOrderCnt(
+      const H264SPS* sps,
+      const H264SliceHeader& slice_hdr,
+      int32_t* pic_order_cnt);
+
+  // Reset computation state. It's best (although not strictly required) to call
+  // this after a seek.
+  void Reset();
+
+ private:
+  int32_t ref_pic_order_cnt_msb_;
+  int32_t ref_pic_order_cnt_lsb_;
+  int32_t prev_frame_num_;
+  int32_t prev_frame_num_offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(H264POC);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_VIDEO_H264_POC_H_