gecko-dev/content/media/MediaSegment.h
2012-07-30 17:20:58 +03:00

271 lines
7.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef MOZILLA_MEDIASEGMENT_H_
#define MOZILLA_MEDIASEGMENT_H_
#include "nsTArray.h"
namespace mozilla {
/**
* We represent media times in 64-bit fixed point. So 1 MediaTime is
* 1/(2^MEDIA_TIME_FRAC_BITS) seconds.
*/
typedef PRInt64 MediaTime;
const PRInt64 MEDIA_TIME_FRAC_BITS = 20;
const PRInt64 MEDIA_TIME_MAX = PR_INT64_MAX;
inline MediaTime MillisecondsToMediaTime(PRInt32 aMS)
{
return (MediaTime(aMS) << MEDIA_TIME_FRAC_BITS)/1000;
}
inline MediaTime SecondsToMediaTime(double aS)
{
NS_ASSERTION(aS <= (MEDIA_TIME_MAX >> MEDIA_TIME_FRAC_BITS),
"Out of range");
return MediaTime(aS * (1 << MEDIA_TIME_FRAC_BITS));
}
inline double MediaTimeToSeconds(MediaTime aTime)
{
return aTime*(1.0/(1 << MEDIA_TIME_FRAC_BITS));
}
/**
* A number of ticks at a rate determined by some underlying track (e.g.
* audio sample rate). We want to make sure that multiplying TrackTicks by
* 2^MEDIA_TIME_FRAC_BITS doesn't overflow, so we set its max accordingly.
*/
typedef PRInt64 TrackTicks;
const PRInt64 TRACK_TICKS_MAX = PR_INT64_MAX >> MEDIA_TIME_FRAC_BITS;
/**
* A MediaSegment is a chunk of media data sequential in time. Different
* types of data have different subclasses of MediaSegment, all inheriting
* from MediaSegmentBase.
* All MediaSegment data is timed using TrackTicks. The actual tick rate
* is defined on a per-track basis. For some track types, this can be
* a fixed constant for all tracks of that type (e.g. 1MHz for video).
*
* Each media segment defines a concept of "null media data" (e.g. silence
* for audio or "no video frame" for video), which can be efficiently
* represented. This is used for padding.
*/
class MediaSegment {
public:
virtual ~MediaSegment()
{
MOZ_COUNT_DTOR(MediaSegment);
}
enum Type {
AUDIO,
VIDEO,
TYPE_COUNT
};
/**
* Gets the total duration of the segment.
*/
TrackTicks GetDuration() { return mDuration; }
Type GetType() { return mType; }
/**
* Create a MediaSegment of the same type.
*/
virtual MediaSegment* CreateEmptyClone() = 0;
/**
* Moves contents of aSource to the end of this segment.
*/
virtual void AppendFrom(MediaSegment* aSource) = 0;
/**
* Replace all contents up to aDuration with null data.
*/
virtual void ForgetUpTo(TrackTicks aDuration) = 0;
/**
* Insert aDuration of null data at the start of the segment.
*/
virtual void InsertNullDataAtStart(TrackTicks aDuration) = 0;
protected:
MediaSegment(Type aType) : mDuration(0), mType(aType)
{
MOZ_COUNT_CTOR(MediaSegment);
}
TrackTicks mDuration; // total of mDurations of all chunks
Type mType;
};
/**
* C is the implementation class subclassed from MediaSegmentBase.
* C must contain a Chunk class.
*/
template <class C, class Chunk> class MediaSegmentBase : public MediaSegment {
public:
virtual MediaSegment* CreateEmptyClone()
{
C* s = new C();
s->InitFrom(*static_cast<C*>(this));
return s;
}
/**
* Appends the contents of aSource to this segment, clearing aSource.
*/
virtual void AppendFrom(MediaSegmentBase<C, Chunk>* aSource)
{
mDuration += aSource->mDuration;
aSource->mDuration = 0;
if (!mChunks.IsEmpty() && !aSource->mChunks.IsEmpty() &&
mChunks[mChunks.Length() - 1].CanCombineWithFollowing(aSource->mChunks[0])) {
mChunks[mChunks.Length() - 1].mDuration += aSource->mChunks[0].mDuration;
aSource->mChunks.RemoveElementAt(0);
}
mChunks.MoveElementsFrom(aSource->mChunks);
}
void RemoveLeading(TrackTicks aDuration)
{
RemoveLeadingInternal(aDuration, 0);
}
virtual void AppendFrom(MediaSegment* aSource)
{
NS_ASSERTION(aSource->GetType() == C::StaticType(), "Wrong type");
AppendFrom(static_cast<C*>(aSource));
}
/**
* Replace the first aDuration ticks with null media data, because the data
* will not be required again.
*/
virtual void ForgetUpTo(TrackTicks aDuration)
{
if (mChunks.IsEmpty() || aDuration <= 0) {
return;
}
if (mChunks[0].IsNull()) {
TrackTicks extraToForget = NS_MIN(aDuration, mDuration) - mChunks[0].GetDuration();
if (extraToForget > 0) {
RemoveLeadingInternal(extraToForget, 1);
mChunks[0].mDuration += extraToForget;
mDuration += extraToForget;
}
return;
}
RemoveLeading(aDuration);
mChunks.InsertElementAt(0)->SetNull(aDuration);
mDuration += aDuration;
}
virtual void InsertNullDataAtStart(TrackTicks aDuration)
{
if (aDuration <= 0) {
return;
}
if (!mChunks.IsEmpty() && mChunks[0].IsNull()) {
mChunks[0].mDuration += aDuration;
} else {
mChunks.InsertElementAt(0)->SetNull(aDuration);
}
mDuration += aDuration;
}
protected:
MediaSegmentBase(Type aType) : MediaSegment(aType) {}
void BaseSliceFrom(const MediaSegmentBase<C, Chunk>& aOther,
TrackTicks aStart, TrackTicks aEnd)
{
NS_ASSERTION(aStart >= 0 && aEnd <= aOther.mDuration,
"Slice out of range");
TrackTicks offset = 0;
for (PRUint32 i = 0; i < aOther.mChunks.Length() && offset < aEnd; ++i) {
const Chunk& c = aOther.mChunks[i];
TrackTicks start = NS_MAX(aStart, offset);
TrackTicks nextOffset = offset + c.GetDuration();
TrackTicks end = NS_MIN(aEnd, nextOffset);
if (start < end) {
mChunks.AppendElement(c)->SliceTo(start - offset, end - offset);
}
offset = nextOffset;
}
}
Chunk* AppendChunk(TrackTicks aDuration)
{
Chunk* c = mChunks.AppendElement();
c->mDuration = aDuration;
mDuration += aDuration;
return c;
}
Chunk* FindChunkContaining(TrackTicks aOffset, TrackTicks* aStart = nullptr)
{
if (aOffset < 0) {
return nullptr;
}
TrackTicks offset = 0;
for (PRUint32 i = 0; i < mChunks.Length(); ++i) {
Chunk& c = mChunks[i];
TrackTicks nextOffset = offset + c.GetDuration();
if (aOffset < nextOffset) {
if (aStart) {
*aStart = offset;
}
return &c;
}
offset = nextOffset;
}
return nullptr;
}
Chunk* GetLastChunk()
{
if (mChunks.IsEmpty()) {
return nullptr;
}
return &mChunks[mChunks.Length() - 1];
}
class ChunkIterator {
public:
ChunkIterator(MediaSegmentBase<C, Chunk>& aSegment)
: mSegment(aSegment), mIndex(0) {}
bool IsEnded() { return mIndex >= mSegment.mChunks.Length(); }
void Next() { ++mIndex; }
Chunk& operator*() { return mSegment.mChunks[mIndex]; }
Chunk* operator->() { return &mSegment.mChunks[mIndex]; }
private:
MediaSegmentBase<C, Chunk>& mSegment;
PRUint32 mIndex;
};
protected:
void RemoveLeadingInternal(TrackTicks aDuration, PRUint32 aStartIndex)
{
NS_ASSERTION(aDuration >= 0, "Can't remove negative duration");
TrackTicks t = aDuration;
PRUint32 chunksToRemove = 0;
for (PRUint32 i = aStartIndex; i < mChunks.Length() && t > 0; ++i) {
Chunk* c = &mChunks[i];
if (c->GetDuration() > t) {
c->SliceTo(t, c->GetDuration());
t = 0;
break;
}
t -= c->GetDuration();
chunksToRemove = i + 1 - aStartIndex;
}
mChunks.RemoveElementsAt(aStartIndex, chunksToRemove);
mDuration -= aDuration - t;
}
nsTArray<Chunk> mChunks;
};
}
#endif /* MOZILLA_MEDIASEGMENT_H_ */