Files
UnrealEngine/Engine/Source/Runtime/Windows/WindowsPlatformFeatures/Private/WmfRingBuffer.cpp
2025-05-18 13:04:45 +08:00

152 lines
3.8 KiB
C++

// Copyright Epic Games, Inc. All Rights Reserved.
#include "WmfRingBuffer.h"
#include "Misc/ScopeLock.h"
DECLARE_LOG_CATEGORY_EXTERN(WmfRingBuffer, Log, VeryVerbose);
DEFINE_LOG_CATEGORY(WmfRingBuffer);
PRAGMA_DISABLE_DEPRECATION_WARNINGS
void FWmfRingBuffer::Push(AVEncoder::FMediaPacket&& Sample)
{
check(MaxDuration != 0);
FScopeLock Lock(&Mutex);
// start always from video sample for simplicity of `Cleanup` impl
if (Samples.Num() == 0 && Sample.Type == AVEncoder::EPacketType::Audio)
{
// drop
}
else if (Samples.Num() == 0)
{
Samples.Add(MoveTemp(Sample));
}
else
// video encoding takes longer than audio thus video encoded samples arrive later and need to be placed
// inside the container. Video also is not strictly timestamp-ordered (maybe due to B-frames)
{
FTimespan TimestampToInsert = Sample.Timestamp;
bool bIsSampleVideoKeyFrame = Sample.IsVideoKeyFrame();
int i = Samples.Num() - 1;
while (true)
{
if (Samples[i].Type == Sample.Type // don't change order of same stream cos video is not strictly timestamp-ordered (B-Frames)
|| TimestampToInsert >= Samples[i].Timestamp)
{
Samples.Insert(MoveTemp(Sample), i + 1);
break;
}
if (i == 0)
{
if (Sample.Type == AVEncoder::EPacketType::Video)
{
Samples.Insert(MoveTemp(Sample), 0);
}
// else: the first sample in the buffer always should be video key-frame, just drop audio sample
// this can happen during debugging due to big gaps in timestamps
break;
}
--i;
}
// cleanup only on receiving key-frame and only when ring-buffer if full
if (!bCleanupPaused && bIsSampleVideoKeyFrame)
{
while (GetDuration() > GetMaxDuration())
{
Cleanup();
}
}
}
}
PRAGMA_ENABLE_DEPRECATION_WARNINGS
void FWmfRingBuffer::Cleanup()
// removes a/v samples grouped by the oldest key-frame period
{
FScopeLock Lock(&Mutex);
check(Samples.Num() != 0);
PRAGMA_DISABLE_DEPRECATION_WARNINGS
check(Samples[0].IsVideoKeyFrame());
PRAGMA_ENABLE_DEPRECATION_WARNINGS
// find the second key-frame
int i = 1; // skip the first sample which is a keyframe
bool bFound = false;
for (; i != Samples.Num(); ++i)
{
PRAGMA_DISABLE_DEPRECATION_WARNINGS
if (Samples[i].IsVideoKeyFrame())
PRAGMA_ENABLE_DEPRECATION_WARNINGS
{
bFound = true;
break;
}
}
check(bFound);
// remove key-frame period
Samples.RemoveAt(0, i, EAllowShrinking::No);
PRAGMA_DISABLE_DEPRECATION_WARNINGS
check(Samples[0].IsVideoKeyFrame());
PRAGMA_ENABLE_DEPRECATION_WARNINGS
PRAGMA_DISABLE_DEPRECATION_WARNINGS
UE_LOG(WmfRingBuffer, VeryVerbose, TEXT("%d samples, %.3f s, %.3f - %.3f:%.3f"),
Samples.Num(),
GetDuration().GetTotalSeconds(),
Samples[0].Timestamp.GetTotalSeconds(),
Samples.Last().Timestamp.GetTotalSeconds(),
Samples.Last().Duration.GetTotalSeconds());
PRAGMA_ENABLE_DEPRECATION_WARNINGS
}
void FWmfRingBuffer::PauseCleanup(bool bPause)
{
bCleanupPaused = bPause;
}
FTimespan FWmfRingBuffer::GetDuration() const
{
if (Samples.Num() == 0)
{
return 0;
}
// A duration of a video is not "LastFrameCaptureTime - FirstFrameCaptureTime" , but
// (LastFrameCaptureTime - FirstFrameCaptureTime) + LastFrameDuration.
PRAGMA_DISABLE_DEPRECATION_WARNINGS
return Samples.Last().Timestamp + Samples.Last().Duration - Samples[0].Timestamp;
PRAGMA_ENABLE_DEPRECATION_WARNINGS
}
PRAGMA_DISABLE_DEPRECATION_WARNINGS
TArray<AVEncoder::FMediaPacket> FWmfRingBuffer::GetCopy()
{
FScopeLock Lock(&Mutex);
TArray<AVEncoder::FMediaPacket> Copy;
// cloning is required because during saving a copy of ring buffer we modify samples timestamps.
// using samples references shared between ring buffer and its copy being saved would cause ring
// buffer timestamp logic corruption
Copy = Samples;
return Copy;
}
PRAGMA_ENABLE_DEPRECATION_WARNINGS
void FWmfRingBuffer::Reset()
{
FScopeLock Lock(&Mutex);
Samples.Empty();
}