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// Copyright (c) 2010 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_BASE_PTS_HEAP_H_
#define MEDIA_BASE_PTS_HEAP_H_
// The compressed frame are often in decode timestamp (dts) order, which
// may not always be in presentation timestamp (pts) order. However, the
// decoded frames will always be returned in pts order. Ideally, the pts could
// be attached as metadata to each comprsesed frame, and the decoder would
// pass it along in the uncompressed frame so that it can be used in render.
// Some decoders, like FFmpeg, do not have this facility, so we use PtsHeap to
// pass along this information and simulate the reodering.
//
// Here is an illustration of why the reordering might be necessary.
//
// Decode PTS of PTS of
// Call # Buffer In Buffer Out
// 1 1 1
// 2 3 --- <--- frame 3 buffered by Decoder
// 3 2 2
// 4 4 3 <--- copying timestamp 4 and 6 would be
// 5 6 4 <-' incorrect, which is why we sort and
// 6 5 5 queue incoming timestamps
//
// The PtsHeap expects that for every Pop(), there was a corresponding Push().
// It will CHECK fail otherwise.
#include <queue>
#include <vector>
#include "base/time.h"
namespace media {
class PtsHeap {
public:
PtsHeap();
~PtsHeap();
void Push(const base::TimeDelta& pts);
void Pop();
const base::TimeDelta& Top() const { return queue_.top(); }
bool IsEmpty() const { return queue_.empty(); }
private:
struct PtsHeapOrdering {
bool operator()(const base::TimeDelta& lhs,
const base::TimeDelta& rhs) const {
// std::priority_queue is a max-heap. We want lower timestamps to show up
// first so reverse the natural less-than comparison.
return rhs < lhs;
}
};
typedef std::priority_queue<base::TimeDelta,
std::vector<base::TimeDelta>,
PtsHeapOrdering> TimeQueue;
TimeQueue queue_;
DISALLOW_COPY_AND_ASSIGN(PtsHeap);
};
} // namespace media
#endif // MEDIA_BASE_PTS_HEAP_H_
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