h264_dpb.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4//
5// This file contains an implementation of an H.264 Decoded Picture Buffer
6// used in H264 decoders.
7
8#ifndef CONTENT_COMMON_GPU_MEDIA_H264_DPB_H_
9#define CONTENT_COMMON_GPU_MEDIA_H264_DPB_H_
10
11#include <vector>
12
13#include "base/basictypes.h"
14#include "base/memory/scoped_vector.h"
15#include "content/common/gpu/media/h264_parser.h"
16
17namespace content {
18
19// A picture (a frame or a field) in the H.264 spec sense.
20// See spec at http://www.itu.int/rec/T-REC-H.264
21struct H264Picture {
22  enum Field {
23    FIELD_NONE,
24    FIELD_TOP,
25    FIELD_BOTTOM,
26  };
27
28  // Values calculated per H.264 specification or taken from slice header.
29  // See spec for more details on each (some names have been converted from
30  // CamelCase in spec to Chromium-style names).
31  int top_field_order_cnt;
32  int bottom_field_order_cnt;
33  int pic_order_cnt;
34  int pic_order_cnt_msb;
35  int pic_order_cnt_lsb;
36
37  int pic_num;
38  int long_term_pic_num;
39  int frame_num;  // from slice header
40  int frame_num_offset;
41  int frame_num_wrap;
42  int long_term_frame_idx;
43
44  bool idr;  // IDR picture?
45  bool ref;  // reference picture?
46  bool long_term;  // long term reference picture?
47  bool outputted;
48  // Does memory management op 5 needs to be executed after this
49  // picture has finished decoding?
50  bool mem_mgmt_5;
51
52  Field field;
53
54  // Values from slice_hdr to be used during reference marking and
55  // memory management after finishing this picture.
56  bool long_term_reference_flag;
57  bool adaptive_ref_pic_marking_mode_flag;
58  H264DecRefPicMarking ref_pic_marking[H264SliceHeader::kRefListSize];
59
60  typedef std::vector<H264Picture*> PtrVector;
61};
62
63// DPB - Decoded Picture Buffer.
64// Stores decoded pictures that will be used for future display
65// and/or reference.
66class H264DPB {
67 public:
68  H264DPB();
69  ~H264DPB();
70
71  // Remove unused (not reference and already outputted) pictures from DPB.
72  void RemoveUnused();
73
74  // Remove a picture by its pic_order_cnt.
75  void RemoveByPOC(int poc);
76
77  // Clear DPB.
78  void Clear();
79
80  // Store picture in DPB. DPB takes ownership of its resources.
81  void StorePic(H264Picture* pic);
82
83  // Return the number of reference pictures in DPB.
84  int CountRefPics();
85
86  // Mark all pictures in DPB as unused for reference.
87  void MarkAllUnusedForRef();
88
89  // Return a short-term reference picture by its pic_num.
90  H264Picture* GetShortRefPicByPicNum(int pic_num);
91
92  // Return a long-term reference picture by its long_term_pic_num.
93  H264Picture* GetLongRefPicByLongTermPicNum(int pic_num);
94
95  // Return the short reference picture with lowest frame_num. Used for sliding
96  // window memory management.
97  H264Picture* GetLowestFrameNumWrapShortRefPic();
98
99  // Append all pictures that have not been outputted yet to the passed |out|
100  // vector, sorted by lowest pic_order_cnt (in output order).
101  void GetNotOutputtedPicsAppending(H264Picture::PtrVector& out);
102
103  // Append all short term reference pictures to the passed |out| vector.
104  void GetShortTermRefPicsAppending(H264Picture::PtrVector& out);
105
106  // Append all long term reference pictures to the passed |out| vector.
107  void GetLongTermRefPicsAppending(H264Picture::PtrVector& out);
108
109  // Iterators for direct access to DPB contents.
110  // Will be invalidated after any of Remove* calls.
111  typedef ScopedVector<H264Picture> Pictures;
112  Pictures::iterator begin() { return pics_.begin(); }
113  Pictures::iterator end() { return pics_.end(); }
114  Pictures::reverse_iterator rbegin() { return pics_.rbegin(); }
115  Pictures::reverse_iterator rend() { return pics_.rend(); }
116
117  size_t size() const { return pics_.size(); }
118  bool IsFull() const { return pics_.size() == kDPBMaxSize; }
119
120  // Per H264 spec, increase to 32 if interlaced video is supported.
121  enum { kDPBMaxSize = 16 };
122
123 private:
124  Pictures pics_;
125
126  DISALLOW_COPY_AND_ASSIGN(H264DPB);
127};
128
129}  // namespace content
130
131#endif  // CONTENT_COMMON_GPU_MEDIA_H264_DPB_H_
132