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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 // | 4 // |
5 // This file contains an implementation of an H264 Annex-B video stream parser. | 5 // This file contains an implementation of an H264 Annex-B video stream parser. |
6 | 6 |
7 #ifndef CONTENT_COMMON_GPU_MEDIA_H264_BIT_READER_H_ | 7 #ifndef MEDIA_FILTERS_H264_BIT_READER_H_ |
8 #define CONTENT_COMMON_GPU_MEDIA_H264_BIT_READER_H_ | 8 #define MEDIA_FILTERS_H264_BIT_READER_H_ |
9 | 9 |
10 #include <sys/types.h> | 10 #include <sys/types.h> |
11 | 11 |
12 #include "base/basictypes.h" | 12 #include "base/basictypes.h" |
13 #include "content/common/content_export.h" | 13 #include "media/base/media_export.h" |
14 | 14 |
15 namespace content { | 15 namespace media { |
16 | 16 |
17 // A class to provide bit-granularity reading of H.264 streams. | 17 // A class to provide bit-granularity reading of H.264 streams. |
18 // This is not a generic bit reader class, as it takes into account | 18 // This is not a generic bit reader class, as it takes into account |
19 // H.264 stream-specific constraints, such as skipping emulation-prevention | 19 // H.264 stream-specific constraints, such as skipping emulation-prevention |
20 // bytes and stop bits. See spec for more details. | 20 // bytes and stop bits. See spec for more details. |
21 class CONTENT_EXPORT H264BitReader { | 21 class MEDIA_EXPORT H264BitReader { |
22 public: | 22 public: |
23 H264BitReader(); | 23 H264BitReader(); |
24 ~H264BitReader(); | 24 ~H264BitReader(); |
25 | 25 |
26 // Initialize the reader to start reading at |data|, |size| being size | 26 // Initialize the reader to start reading at |data|, |size| being size |
27 // of |data| in bytes. | 27 // of |data| in bytes. |
28 // Return false on insufficient size of stream.. | 28 // Return false on insufficient size of stream.. |
29 // TODO(posciak,fischman): consider replacing Initialize() with | 29 // TODO(posciak,fischman): consider replacing Initialize() with |
30 // heap-allocating and creating bit readers on demand instead. | 30 // heap-allocating and creating bit readers on demand instead. |
31 bool Initialize(const uint8* data, off_t size); | 31 bool Initialize(const uint8* data, off_t size); |
32 | 32 |
33 // Read |num_bits| next bits from stream and return in |*out|, first bit | 33 // Read |num_bits| next bits from stream and return in |*out|, first bit |
34 // from the stream starting at |num_bits| position in |*out|. | 34 // from the stream starting at |num_bits| position in |*out|. |
35 // |num_bits| may be 1-32, inclusive. | 35 // |num_bits| may be 1-32, inclusive. |
36 // Return false if the given number of bits cannot be read (not enough | 36 // Return false if the given number of bits cannot be read (not enough |
37 // bits in the stream), true otherwise. | 37 // bits in the stream), true otherwise. |
38 bool ReadBits(int num_bits, int *out); | 38 bool ReadBits(int num_bits, int* out); |
39 | 39 |
40 // Return the number of bits left in the stream. | 40 // Return the number of bits left in the stream. |
41 off_t NumBitsLeft(); | 41 off_t NumBitsLeft(); |
42 | 42 |
43 // See the definition of more_rbsp_data() in spec. | 43 // See the definition of more_rbsp_data() in spec. |
44 bool HasMoreRBSPData(); | 44 bool HasMoreRBSPData(); |
45 | 45 |
46 // Return the number of emulation prevention bytes already read. | 46 // Return the number of emulation prevention bytes already read. |
47 size_t NumEmulationPreventionBytesRead(); | 47 size_t NumEmulationPreventionBytesRead(); |
48 | 48 |
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67 // Used in emulation prevention three byte detection (see spec). | 67 // Used in emulation prevention three byte detection (see spec). |
68 // Initially set to 0xffff to accept all initial two-byte sequences. | 68 // Initially set to 0xffff to accept all initial two-byte sequences. |
69 int prev_two_bytes_; | 69 int prev_two_bytes_; |
70 | 70 |
71 // Number of emulation preventation bytes (0x000003) we met. | 71 // Number of emulation preventation bytes (0x000003) we met. |
72 size_t emulation_prevention_bytes_; | 72 size_t emulation_prevention_bytes_; |
73 | 73 |
74 DISALLOW_COPY_AND_ASSIGN(H264BitReader); | 74 DISALLOW_COPY_AND_ASSIGN(H264BitReader); |
75 }; | 75 }; |
76 | 76 |
77 } // namespace content | 77 } // namespace media |
78 | 78 |
79 #endif // CONTENT_COMMON_GPU_MEDIA_H264_BIT_READER_H_ | 79 #endif // MEDIA_FILTERS_H264_BIT_READER_H_ |
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