Move the Vsync logic from VTRenderer into a VsyncSource

app/streaming/video/ffmpeg-renderers/vt.mm

@@ -2,18 +2,18 @@
 // libavutil both defining AVMediaType
 #define AVMediaType AVMediaType_FFmpeg
 #include "vt.h"
-#include "pacer.h"
+#include "pacer/pacer.h"
 #undef AVMediaType
 
 #include <SDL_syswm.h>
 #include <Limelight.h>
 
+#include <mach/mach_time.h>
 #import <Cocoa/Cocoa.h>
 #import <VideoToolbox/VideoToolbox.h>
 #import <AVFoundation/AVFoundation.h>
-#import <CoreVideo/CoreVideo.h>
 
-class VTRenderer : public IFFmpegRenderer
+class VTRenderer : public IFFmpegRenderer, public IVsyncRenderer
 {
 public:
     VTRenderer()
@@ -21,7 +21,7 @@ public:
           m_DisplayLayer(nullptr),
           m_FormatDesc(nullptr),
           m_View(nullptr),
-          m_DisplayLink(nullptr)
+          m_Pacer(this)
     {
     }
 
@@ -37,25 +37,15 @@ public:
             CFRelease(m_FormatDesc);
         }
 
-        if (m_DisplayLink != nullptr) {
-            CVDisplayLinkStop(m_DisplayLink);
-            CVDisplayLinkRelease(m_DisplayLink);
-        }
-
         if (m_View != nullptr) {
             [m_View removeFromSuperview];
         }
     }
 
-    void drawFrame(uint64_t vsyncTime)
+    // Caller frees frame after we return
+    virtual void renderFrameAtVsync(AVFrame* frame) override
     {
         OSStatus status;
-
-        AVFrame* frame = m_Pacer.getFrameAtVsync();
-        if (frame == nullptr) {
-            return;
-        }
-
         CVPixelBufferRef pixBuf = reinterpret_cast<CVPixelBufferRef>(frame->data[3]);
 
         // If the format has changed or doesn't exist yet, construct it with the
@@ -70,7 +60,6 @@ public:
                 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                              "CMVideoFormatDescriptionCreateForImageBuffer() failed: %d",
                              status);
-                av_frame_free(&frame);
                 return;
             }
         }
@@ -79,7 +68,7 @@ public:
         CMSampleTimingInfo timingInfo = {
             .duration = kCMTimeInvalid,
             .decodeTimeStamp = kCMTimeInvalid,
-            .presentationTimeStamp = CMTimeMake(vsyncTime, 1000 * 1000 * 1000)
+            .presentationTimeStamp = CMTimeMake(mach_absolute_time(), 1000 * 1000 * 1000)
         };
 
         CMSampleBufferRef sampleBuffer;
@@ -92,39 +81,12 @@ public:
             SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                          "CMSampleBufferCreateReadyWithImageBuffer() failed: %d",
                          status);
-            av_frame_free(&frame);
             return;
         }
 
         [m_DisplayLayer enqueueSampleBuffer:sampleBuffer];
 
         CFRelease(sampleBuffer);
-        av_frame_free(&frame);
-    }
-
-    static
-    CVReturn
-    displayLinkOutputCallback(
-        CVDisplayLinkRef,
-        const CVTimeStamp* now,
-        const CVTimeStamp* /* vsyncTime */,
-        CVOptionFlags,
-        CVOptionFlags*,
-        void *displayLinkContext)
-    {
-        VTRenderer* me = reinterpret_cast<VTRenderer*>(displayLinkContext);
-
-        // In my testing on macOS 10.13, this callback is invoked about 24 ms
-        // prior to the specified v-sync time (now - vsyncTime). Since this is
-        // greater than the standard v-sync interval (16 ms = 60 FPS), we will
-        // draw using the current host time, rather than the actual v-sync target
-        // time. Because the CVDisplayLink is in sync with the actual v-sync
-        // interval, even if many ms prior, we can safely use the current host time
-        // and get a consistent callback for each v-sync. This reduces video latency
-        // by at least 1 frame vs. rendering with the actual vsyncTime.
-        me->drawFrame(now->hostTime);
-
-        return kCVReturnSuccess;
     }
 
     virtual bool initialize(SDL_Window* window,
@@ -135,7 +97,9 @@ public:
     {
         int err;
 
-        m_Pacer.initialize(window, maxFps);
+        if (!m_Pacer.initialize(window, maxFps)) {
+            return false;
+        }
 
         if (videoFormat & VIDEO_FORMAT_MASK_H264) {
             // Prior to 10.13, we'll just assume everything has
@@ -208,10 +172,6 @@ public:
             return false;
         }
 
-        CVDisplayLinkCreateWithActiveCGDisplays(&m_DisplayLink);
-        CVDisplayLinkSetOutputCallback(m_DisplayLink, displayLinkOutputCallback, this);
-        CVDisplayLinkStart(m_DisplayLink);
-
         return true;
     }
 
@@ -259,7 +219,6 @@ private:
     AVSampleBufferDisplayLayer* m_DisplayLayer;
     CMVideoFormatDescriptionRef m_FormatDesc;
     NSView* m_View;
-    CVDisplayLinkRef m_DisplayLink;
     Pacer m_Pacer;
 };