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 // Timestamps are derived directly from the encoded media file and are commonly 6 // known as the presentation timestamp (PTS). Durations are a best-guess and 7 // are usually derived from the sample/frame rate of the media file. 8 // 9 // Due to encoding and transmission errors, it is not guaranteed that timestamps 10 // arrive in a monotonically increasing order nor that the next timestamp will 11 // be equal to the previous timestamp plus the duration. 12 // 13 // In the ideal scenario for a 25fps movie, buffers are timestamped as followed: 14 // 15 // Buffer0 Buffer1 Buffer2 ... BufferN 16 // Timestamp: 0us 40000us 80000us ... (N*40000)us 17 // Duration*: 40000us 40000us 40000us ... 40000us 18 // 19 // *25fps = 0.04s per frame = 40000us per frame 20 21 #ifndef MEDIA_BASE_BUFFERS_H_ 22 #define MEDIA_BASE_BUFFERS_H_ 23 24 #include "base/basictypes.h" 25 #include "base/memory/ref_counted.h" 26 #include "base/time/time.h" 27 #include "media/base/media_export.h" 28 29 namespace media { 30 31 // TODO(scherkus): Move the contents of this file elsewhere. 32 33 // Indicates an invalid or missing timestamp. 34 MEDIA_EXPORT extern inline base::TimeDelta kNoTimestamp() { 35 return base::TimeDelta::FromMicroseconds(kint64min); 36 } 37 38 // Represents an infinite stream duration. 39 MEDIA_EXPORT extern inline base::TimeDelta kInfiniteDuration() { 40 return base::TimeDelta::FromMicroseconds(kint64max); 41 } 42 43 } // namespace media 44 45 #endif // MEDIA_BASE_BUFFERS_H_ 46
