avfvideosrc: setjmp/longjmp patch

applemedia-setjmp-longjmp.patch

From c3199506fd03e77b61cd6fdfbd8184e1effb28ba Mon Sep 17 00:00:00 2001
From: Ilya Konstantinov <ilya.konstantinov@gmail.com>
Date: Sun, 5 Apr 2015 05:39:14 +0300
Subject: [PATCH] applemedia: setjmp/longjmp

Migrate the pipeline into the AVFoundation dispatch queue thread
to enable operation without context switching and unneeded yielding.
---
 sys/applemedia/avfvideosrc.m | 101 ++++++++++++++++++++++++++++---------------
 1 file changed, 66 insertions(+), 35 deletions(-)

diff --git a/sys/applemedia/avfvideosrc.m b/sys/applemedia/avfvideosrc.m
index 6aa084c..6819906 100644
--- a/sys/applemedia/avfvideosrc.m
+++ b/sys/applemedia/avfvideosrc.m
@@ -68,8 +68,8 @@ static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
 ));
 
 typedef enum _QueueState {
-  NO_BUFFERS = 1,
-  HAS_BUFFER_OR_STOP_REQUEST,
+  RUNNING = 1,
+  STOP_REQUEST,
 } QueueState;
 
 #define gst_avf_video_src_parent_class parent_class
@@ -92,7 +92,8 @@ G_DEFINE_TYPE (GstAVFVideoSrc, gst_avf_video_src, GST_TYPE_PUSH_SRC);
   dispatch_queue_t mainQueue;
   dispatch_queue_t workerQueue;
   NSConditionLock *bufQueueLock;
-  NSMutableArray *bufQueue;
+  CMSampleBufferRef delegateSampleBuffer;
+  GstClockTime timestamp, duration;
   BOOL stopRequest;
 
   GstCaps *caps;
@@ -112,6 +113,9 @@ G_DEFINE_TYPE (GstAVFVideoSrc, gst_avf_video_src, GST_TYPE_PUSH_SRC);
 
   BOOL useVideoMeta;
   GstCoreVideoTextureCache *textureCache;
+
+  BOOL envCreateValid, envCaptureOutputValid;
+  jmp_buf env_create, env_captureOutput;
 }
 
 - (id)init;
@@ -184,6 +188,9 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
 
     gst_base_src_set_live (baseSrc, TRUE);
     gst_base_src_set_format (baseSrc, GST_FORMAT_TIME);
+
+    envCreateValid = FALSE;
+    envCaptureOutputValid = FALSE;
   }
 
   return self;
@@ -369,6 +376,7 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
   case kCVPixelFormatType_422YpCbCr8_yuvs: /* yuvs */
     gst_format = GST_VIDEO_FORMAT_YUY2;
     break;
+  case kCVPixelFormatType_420YpCbCr8BiPlanarFullRange: /* 420f (full range 420v) */
   default:
     GST_LOG_OBJECT (element, "Pixel format %s is not handled by avfvideosrc",
         [[pixel_format stringValue] UTF8String]);
@@ -710,8 +718,7 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
 
 - (BOOL)start
 {
-  bufQueueLock = [[NSConditionLock alloc] initWithCondition:NO_BUFFERS];
-  bufQueue = [[NSMutableArray alloc] initWithCapacity:BUFFER_QUEUE_SIZE];
+  bufQueueLock = [[NSConditionLock alloc] initWithCondition:RUNNING];
   stopRequest = NO;
 
   offset = 0;
@@ -734,8 +741,6 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
 
   [bufQueueLock release];
   bufQueueLock = nil;
-  [bufQueue release];
-  bufQueue = nil;
   inputClock = nil;
 
   if (textureCache)
@@ -803,7 +808,7 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
 {
   [bufQueueLock lock];
   stopRequest = YES;
-  [bufQueueLock unlockWithCondition:HAS_BUFFER_OR_STOP_REQUEST];
+  [bufQueueLock unlockWithCondition:STOP_REQUEST];
 
   return YES;
 }
@@ -838,12 +843,11 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
 didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
        fromConnection:(AVCaptureConnection *)connection
 {
-  GstClockTime timestamp, duration;
-
-  [bufQueueLock lock];
+  if (!envCreateValid) {
+    return;
+  }
 
   if (stopRequest) {
-    [bufQueueLock unlock];
     return;
   }
 
@@ -851,15 +855,14 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
     inputClock = ((AVCaptureInputPort *)connection.inputPorts[0]).clock;
   [self getSampleBuffer:sampleBuffer timestamp:&timestamp duration:&duration];
 
-  if ([bufQueue count] == BUFFER_QUEUE_SIZE)
-    [bufQueue removeLastObject];
+  delegateSampleBuffer = sampleBuffer;
 
-  [bufQueue insertObject:@{@"sbuf": (id)sampleBuffer,
-                           @"timestamp": @(timestamp),
-                           @"duration": @(duration)}
-                 atIndex:0];
-
-  [bufQueueLock unlockWithCondition:HAS_BUFFER_OR_STOP_REQUEST];
+  if (!setjmp (env_captureOutput)) {
+    envCaptureOutputValid = TRUE;
+    longjmp (env_create, 1); // back to create:
+  } else {
+    return; /* continuing captureOutput */
+  }
 }
 
 - (GstFlowReturn)create:(GstBuffer **)buf
@@ -868,22 +871,48 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
   CVImageBufferRef image_buf;
   CVPixelBufferRef pixel_buf;
   size_t cur_width, cur_height;
-  GstClockTime timestamp, duration;
 
-  [bufQueueLock lockWhenCondition:HAS_BUFFER_OR_STOP_REQUEST];
-  if (stopRequest) {
+  if (!setjmp (env_create)) {
+    envCreateValid = TRUE; /* mark this as jumpable */
+
+    if (envCaptureOutputValid) {
+       /* We've come full circle. We've pushed one buffer into the
+        * pipeline, we've been called against by GstBaseSrc,
+        * and now we're ready to give the delegate an opportunity
+        * to get another sample buffer.
+        *
+        * Of course, at this point we're on the AVFoundation thread.
+        * 
+        * longjmp into delegate
+        * captureOutput:didOutputSampleBuffer:fromConnection:
+        */
+      longjmp (env_captureOutput, 1);
+    }
+
+    /* The original pipeline thread is sleeping until it's time
+     * to flush the pipeline. */
+
+    [bufQueueLock lockWhenCondition:STOP_REQUEST];
+    g_assert (stopRequest);
     [bufQueueLock unlock];
+
     return GST_FLOW_FLUSHING;
+
+  } else {
+    /* Arriving in longjmp from delegate
+     * captureOutput:didOutputSampleBuffer:fromConnection:
+     *
+     * This is the delegate giving us opportunity to run the pipeline.
+     * At this point, we're running on the AVFoundation thread.
+     */
+
+    sbuf = delegateSampleBuffer;
   }
 
-  NSDictionary *dic = (NSDictionary *) [bufQueue lastObject];
-  sbuf = (CMSampleBufferRef) dic[@"sbuf"];
-  timestamp = (GstClockTime) [dic[@"timestamp"] longLongValue];
-  duration = (GstClockTime) [dic[@"duration"] longLongValue];
-  CFRetain (sbuf);
-  [bufQueue removeLastObject];
-  [bufQueueLock unlockWithCondition:
-      ([bufQueue count] == 0) ? NO_BUFFERS : HAS_BUFFER_OR_STOP_REQUEST];
+  /* We have to create the autorelease pool here, now that we're
+   * on the AVFoundation thread since autorelease pools seem to have
+   * thread affinity. */
+  NSAutoreleasePool *poolOnAvfThread = [[NSAutoreleasePool alloc] init];
 
   /* Check output frame size dimensions */
   image_buf = CMSampleBufferGetImageBuffer (sbuf);
@@ -916,11 +945,11 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       video_meta->format = format;
     }
   }
-  CFRelease (sbuf);
 
   if (textureCache != NULL) {
     *buf = gst_core_video_texture_cache_get_gl_buffer (textureCache, *buf);
     if (*buf == NULL) {
+      [poolOnAvfThread release];
       return GST_FLOW_ERROR;
     }
   }
@@ -933,6 +962,9 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
   if (doStats)
     [self updateStatistics];
 
+  /* Remember to release the autorelease pool on every return */
+  [poolOnAvfThread release];
+
   return GST_FLOW_OK;
 }
 
@@ -941,7 +973,7 @@ didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
                duration:(GstClockTime *)outDuration
 {
   CMSampleTimingInfo time_info;
-  GstClockTime timestamp, duration, inputClockNow, running_time;
+  GstClockTime inputClockNow, running_time;
   CMItemCount num_timings;
   GstClock *clock;
   CMTime now;
@@ -1318,9 +1350,8 @@ gst_avf_video_src_create (GstPushSrc * pushsrc, GstBuffer ** buf)
 {
   GstFlowReturn ret;
 
-  OBJC_CALLOUT_BEGIN ();
+  /* autorelease pool is done differently here */
   ret = [GST_AVF_VIDEO_SRC_IMPL (pushsrc) create: buf];
-  OBJC_CALLOUT_END ();
 
   return ret;
 }
-- 
2.2.1