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Commit 1585c4d9 authored by Andy McFadden's avatar Andy McFadden
Browse files

Pay attention to buffer timestamps 

When acquiring a buffer, SurfaceFlinger now computes the expected
presentation time and passes it to the BufferQueue acquireBuffer()
method.  If it's not yet time to display the buffer, acquireBuffer()
returns PRESENT_LATER instead of a buffer.

The current implementation of the expected-present-time computation
uses approximations and guesswork.

Bug 7900302

Change-Id: If9345611c5983a11a811935aaf27d6388a5036f1
parent 06b6aed2

include/gui/BufferItemConsumer.h

+2 −1
Original line number Diff line number Diff line
@@ -71,7 +71,8 @@ class BufferItemConsumer: public ConsumerBase 
    //

    // If waitForFence is true, and the acquired BufferItem has a valid fence object,

    // acquireBuffer will wait on the fence with no timeout before returning.

    status_t acquireBuffer(BufferItem *item, bool waitForFence = true);

    status_t acquireBuffer(BufferItem *item, nsecs_t presentWhen,

        bool waitForFence = true);



    // Returns an acquired buffer to the queue, allowing it to be reused. Since

    // only a fixed number of buffers may be acquired at a time, old buffers

include/gui/BufferQueue.h

+8 −2
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ public: 
    enum { NUM_BUFFER_SLOTS = 32 };

    enum { NO_CONNECTED_API = 0 };

    enum { INVALID_BUFFER_SLOT = -1 };

    enum { STALE_BUFFER_SLOT = 1, NO_BUFFER_AVAILABLE };

    enum { STALE_BUFFER_SLOT = 1, NO_BUFFER_AVAILABLE, PRESENT_LATER };



    // When in async mode we reserve two slots in order to guarantee that the

    // producer and consumer can run asynchronously.
@@ -284,7 +284,13 @@ public: 
    // acquired then the BufferItem::mGraphicBuffer field of buffer is set to

    // NULL and it is assumed that the consumer still holds a reference to the

    // buffer.

    status_t acquireBuffer(BufferItem *buffer);

    //

    // If presentWhen is nonzero, it indicates the time when the buffer will

    // be displayed on screen.  If the buffer's timestamp is farther in the

    // future, the buffer won't be acquired, and PRESENT_LATER will be

    // returned.  The presentation time is in nanoseconds, and the time base

    // is CLOCK_MONOTONIC.

    status_t acquireBuffer(BufferItem *buffer, nsecs_t presentWhen);



    // releaseBuffer releases a buffer slot from the consumer back to the

    // BufferQueue.  This may be done while the buffer's contents are still

include/gui/ConsumerBase.h

+2 −1
Original line number Diff line number Diff line
@@ -152,7 +152,8 @@ protected: 
    // initialization that must take place the first time a buffer is assigned

    // to a slot.  If it is overridden the derived class's implementation must

    // call ConsumerBase::acquireBufferLocked.

    virtual status_t acquireBufferLocked(BufferQueue::BufferItem *item);

    virtual status_t acquireBufferLocked(BufferQueue::BufferItem *item,

        nsecs_t presentWhen);



    // releaseBufferLocked relinquishes control over a buffer, returning that

    // control to the BufferQueue.

include/gui/GLConsumer.h

+2 −1
Original line number Diff line number Diff line
@@ -237,7 +237,8 @@ protected: 


    // acquireBufferLocked overrides the ConsumerBase method to update the

    // mEglSlots array in addition to the ConsumerBase behavior.

    virtual status_t acquireBufferLocked(BufferQueue::BufferItem *item);

    virtual status_t acquireBufferLocked(BufferQueue::BufferItem *item,

        nsecs_t presentWhen);



    // releaseBufferLocked overrides the ConsumerBase method to update the

    // mEglSlots array in addition to the ConsumerBase.

libs/gui/BufferItemConsumer.cpp

+3 −2
Original line number Diff line number Diff line
@@ -47,14 +47,15 @@ void BufferItemConsumer::setName(const String8& name) { 
    mBufferQueue->setConsumerName(name);

}



status_t BufferItemConsumer::acquireBuffer(BufferItem *item, bool waitForFence) {

status_t BufferItemConsumer::acquireBuffer(BufferItem *item,

        nsecs_t presentWhen, bool waitForFence) {

    status_t err;



    if (!item) return BAD_VALUE;



    Mutex::Autolock _l(mMutex);



    err = acquireBufferLocked(item);

    err = acquireBufferLocked(item, presentWhen);

    if (err != OK) {

        if (err != NO_BUFFER_AVAILABLE) {

            BI_LOGE("Error acquiring buffer: %s (%d)", strerror(err), err);