blob: e165768b97f35b1bb57f0ad098b14ec86fbaec59 [file] [log] [blame]
* Copyright (C) 2022 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <queue>
#include <gui/Surface.h>
#include <utils/Condition.h>
#include <utils/Mutex.h>
#include <utils/Thread.h>
#include <utils/Timers.h>
namespace android {
namespace camera3 {
class Camera3OutputStream;
* Preview stream spacer for better frame spacing
* The ideal viewfinder user experience is that frames are presented to the
* user in the same cadence as outputed by the camera sensor. However, the
* processing latency between frames could vary, due to factors such
* as CPU load, differences in request settings, etc. This frame processing
* latency results in variation in presentation of frames to the user.
* The PreviewFrameSpacer improves the viewfinder user experience by:
* - Cache the frame buffers if the intervals between queueBuffer is shorter
* than the camera readout intervals.
* - Queue frame buffers in the same cadence as the camera readout time.
* - Maintain at most 1 queue-able buffer. If the 2nd preview buffer becomes
* available, queue the oldest cached buffer to the buffer queue.
class PreviewFrameSpacer : public Thread {
explicit PreviewFrameSpacer(wp<Camera3OutputStream> parent, sp<Surface> consumer);
virtual ~PreviewFrameSpacer();
// Queue preview buffer locally
status_t queuePreviewBuffer(nsecs_t timestamp, nsecs_t readoutTimestamp,
int32_t transform, ANativeWindowBuffer* anwBuffer, int releaseFence);
bool threadLoop() override;
void requestExit() override;
// structure holding cached preview buffer info
struct BufferHolder {
nsecs_t timestamp;
nsecs_t readoutTimestamp;
int32_t transform;
sp<ANativeWindowBuffer> anwBuffer;
int releaseFence;
BufferHolder(nsecs_t t, nsecs_t readoutT, int32_t tr, ANativeWindowBuffer* anwb, int rf) :
timestamp(t), readoutTimestamp(readoutT), transform(tr), anwBuffer(anwb),
releaseFence(rf) {}
void queueBufferToClientLocked(const BufferHolder& bufferHolder, nsecs_t currentTime);
wp<Camera3OutputStream> mParent;
sp<ANativeWindow> mConsumer;
mutable Mutex mLock;
Condition mBufferCond;
std::queue<BufferHolder> mPendingBuffers;
nsecs_t mLastCameraReadoutTime = 0;
nsecs_t mLastCameraPresentTime = 0;
static constexpr nsecs_t kWaitDuration = 5000000LL; // 50ms
static constexpr nsecs_t kFrameIntervalThreshold = 80000000LL; // 80ms
static constexpr nsecs_t kMaxFrameWaitTime = 33333333LL; // 33ms
}; //namespace camera3
}; //namespace android