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Require several consecutive long render times to drop a frame

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This commit is contained in:
Cameron Gutman 2019-01-21 17:58:42 -08:00
parent 58b77cf589
commit 1f972b1828
2 changed files with 37 additions and 16 deletions
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49
app/streaming/video/ffmpeg-renderers/pacer/pacer.cpp
View file

@ -12,6 +12,7 @@
#endif
#define FRAME_HISTORY_ENTRIES 8
#define RENDER_TIME_HISTORY_ENTRIES 8
// We may be woken up slightly late so don't go all the way
// up to the next V-sync since we may accidentally step into
@ -22,7 +23,6 @@
Pacer::Pacer(IFFmpegRenderer* renderer, PVIDEO_STATS videoStats) :
m_FrameQueueLock(0),
m_DropNextFrame(false),
m_VsyncSource(nullptr),
m_VsyncRenderer(renderer),
m_MaxVideoFps(0),
@ -65,8 +65,8 @@ void Pacer::vsyncCallback(int timeUntilNextVsyncMillis)
// frame history to drop frames only if consistently above the
// one queued frame mark.
if (m_MaxVideoFps >= m_DisplayFps) {
for (int i = 0; i < m_FrameQueueHistory.count(); i++) {
if (m_FrameQueueHistory[i] <= 1) {
for (int queueHistoryEntry : m_FrameQueueHistory) {
if (queueHistoryEntry <= 1) {
// Be lenient as long as the queue length
// resolves before the end of frame history
frameDropTarget = 3;
@ -104,7 +104,7 @@ void Pacer::vsyncCallback(int timeUntilNextVsyncMillis)
}
// Nothing to render at this time. This counts as a drop.
m_DropNextFrame = false;
addRenderTimeToHistory(0);
return;
}
@ -148,13 +148,40 @@ bool Pacer::initialize(SDL_Window* window, int maxVideoFps, bool enablePacing)
return true;
}
void Pacer::addRenderTimeToHistory(int renderTime)
{
if (m_RenderTimeHistory.count() == RENDER_TIME_HISTORY_ENTRIES) {
m_RenderTimeHistory.dequeue();
}
m_RenderTimeHistory.enqueue(renderTime);
}
void Pacer::renderFrame(AVFrame* frame)
{
bool dropFrame = !m_RenderTimeHistory.isEmpty();
// If rendering consistently takes longer than an entire V-sync interval,
// there must have been frames pending in the pipeline that are blocking us.
// Drop our this frame to clear the backed up display pipeline.
for (int renderTime : m_RenderTimeHistory) {
if (renderTime <= 1000 / m_DisplayFps) {
dropFrame = false;
break;
}
}
// Drop this frame if we believe we've run into V-sync waits
if (m_DropNextFrame) {
if (dropFrame) {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Render time (%d ms) consistently exceeded V-sync period; dropping frame to reduce latency",
m_RenderTimeHistory[0]);
// Add 0 render time to history to account for the drop
addRenderTimeToHistory(0);
m_VideoStats->pacerDroppedFrames++;
av_frame_free(&frame);
m_DropNextFrame = false;
return;
}
@ -166,15 +193,7 @@ void Pacer::renderFrame(AVFrame* frame)
m_VsyncRenderer->renderFrameAtVsync(frame);
Uint32 afterRender = SDL_GetTicks();
// If rendering took longer than an entire V-sync interval,
// there must have been a frame pending display that blocked us.
// Drop our next frame to clear the backed up display pipeline.
if (afterRender - beforeRender > 1000 / m_DisplayFps) {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Render time exceeded V-sync period (%d ms); dropping next frame to reduce latency",
afterRender - beforeRender);
m_DropNextFrame = true;
}
addRenderTimeToHistory(afterRender - beforeRender);
m_VideoStats->totalRenderTime += afterRender - beforeRender;
m_VideoStats->renderedFrames++;

4
app/streaming/video/ffmpeg-renderers/pacer/pacer.h
View file

@ -27,12 +27,14 @@ public:
bool isUsingFrameQueue();
private:
void addRenderTimeToHistory(int renderTime);
void renderFrame(AVFrame* frame);
QQueue<AVFrame*> m_FrameQueue;
QQueue<int> m_FrameQueueHistory;
QQueue<int> m_RenderTimeHistory;
SDL_SpinLock m_FrameQueueLock;
bool m_DropNextFrame;
IVsyncSource* m_VsyncSource;
IFFmpegRenderer* m_VsyncRenderer;