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1 // Copyright 2014 The Chromium Authors. All rights reserved. | 1 // Copyright 2014 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 #ifndef MEDIA_BASE_AUDIO_DISCARD_HELPER_H_ | 5 #ifndef MEDIA_BASE_AUDIO_DISCARD_HELPER_H_ |
6 #define MEDIA_BASE_AUDIO_DISCARD_HELPER_H_ | 6 #define MEDIA_BASE_AUDIO_DISCARD_HELPER_H_ |
7 | 7 |
8 #include <stddef.h> | 8 #include <stddef.h> |
9 | 9 |
10 #include "base/macros.h" | 10 #include "base/macros.h" |
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23 class MEDIA_EXPORT AudioDiscardHelper { | 23 class MEDIA_EXPORT AudioDiscardHelper { |
24 public: | 24 public: |
25 // |sample_rate| is the sample rate of decoded data which will be handed into | 25 // |sample_rate| is the sample rate of decoded data which will be handed into |
26 // the ProcessBuffers() call. | 26 // the ProcessBuffers() call. |
27 // | 27 // |
28 // |decoder_delay| is the number of frames a decoder will output before data | 28 // |decoder_delay| is the number of frames a decoder will output before data |
29 // corresponding to the first encoded buffer is output. Callers only need to | 29 // corresponding to the first encoded buffer is output. Callers only need to |
30 // specify this if the decoder inserts frames which have no corresponding | 30 // specify this if the decoder inserts frames which have no corresponding |
31 // encoded buffer. | 31 // encoded buffer. |
32 // | 32 // |
| 33 // |delayed_discard| indicates that the codec requires two encoded buffers |
| 34 // before the first decoded output buffer. Used only for vorbis currently. |
| 35 // |
33 // For example, most MP3 decoders will output 529 junk frames before the data | 36 // For example, most MP3 decoders will output 529 junk frames before the data |
34 // corresponding to the first encoded buffer is output. These frames are not | 37 // corresponding to the first encoded buffer is output. These frames are not |
35 // represented in the encoded data stream and instead are an artifact of how | 38 // represented in the encoded data stream and instead are an artifact of how |
36 // most MP3 decoders work. See http://lame.sourceforge.net/tech-FAQ.txt | 39 // most MP3 decoders work. See http://lame.sourceforge.net/tech-FAQ.txt |
37 AudioDiscardHelper(int sample_rate, size_t decoder_delay); | 40 AudioDiscardHelper(int sample_rate, |
| 41 size_t decoder_delay, |
| 42 bool delayed_discard); |
38 ~AudioDiscardHelper(); | 43 ~AudioDiscardHelper(); |
39 | 44 |
40 // Converts a TimeDelta to a frame count based on the constructed sample rate. | 45 // Converts a TimeDelta to a frame count based on the constructed sample rate. |
41 // |duration| must be positive. | 46 // |duration| must be positive. |
42 size_t TimeDeltaToFrames(base::TimeDelta duration) const; | 47 size_t TimeDeltaToFrames(base::TimeDelta duration) const; |
43 | 48 |
44 // Resets internal state and indicates that |initial_discard| of upcoming | 49 // Resets internal state and indicates that |initial_discard| of upcoming |
45 // frames should be discarded. | 50 // frames should be discarded. |
46 void Reset(size_t initial_discard); | 51 void Reset(size_t initial_discard); |
47 | 52 |
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83 // associated buffer. | 88 // associated buffer. |
84 size_t discard_frames_; | 89 size_t discard_frames_; |
85 | 90 |
86 // The last encoded buffer timestamp seen by ProcessBuffers() or kNoTimestamp | 91 // The last encoded buffer timestamp seen by ProcessBuffers() or kNoTimestamp |
87 // if no buffers have been seen thus far. Used to issue warnings for buffer | 92 // if no buffers have been seen thus far. Used to issue warnings for buffer |
88 // sequences with non-monotonic timestamps. | 93 // sequences with non-monotonic timestamps. |
89 base::TimeDelta last_input_timestamp_; | 94 base::TimeDelta last_input_timestamp_; |
90 | 95 |
91 // Certain codecs require two encoded buffers before they'll output the first | 96 // Certain codecs require two encoded buffers before they'll output the first |
92 // decoded buffer. In this case DiscardPadding must be carried over from the | 97 // decoded buffer. In this case DiscardPadding must be carried over from the |
93 // previous encoded buffer. Enabled automatically if an encoded buffer is | 98 // previous encoded buffer. Set during construction. |
94 // given to ProcessBuffers() with a NULL decoded buffer. | 99 const bool delayed_discard_; |
95 bool delayed_discard_; | |
96 DecoderBuffer::DiscardPadding delayed_discard_padding_; | 100 DecoderBuffer::DiscardPadding delayed_discard_padding_; |
97 | 101 |
98 // When |decoder_delay_| > 0, the number of frames which should be discarded | 102 // When |decoder_delay_| > 0, the number of frames which should be discarded |
99 // from the next buffer. The index at which to start discarding is calculated | 103 // from the next buffer. The index at which to start discarding is calculated |
100 // by subtracting |delayed_end_discard_| from |decoder_delay_|. | 104 // by subtracting |delayed_end_discard_| from |decoder_delay_|. |
101 size_t delayed_end_discard_; | 105 size_t delayed_end_discard_; |
102 | 106 |
103 DISALLOW_IMPLICIT_CONSTRUCTORS(AudioDiscardHelper); | 107 DISALLOW_IMPLICIT_CONSTRUCTORS(AudioDiscardHelper); |
104 }; | 108 }; |
105 | 109 |
106 } // namespace media | 110 } // namespace media |
107 | 111 |
108 #endif // MEDIA_BASE_AUDIO_DISCARD_HELPER_H_ | 112 #endif // MEDIA_BASE_AUDIO_DISCARD_HELPER_H_ |
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