From 1f33caa3b3445df1e8107ca2b2af53073d8c282d Mon Sep 17 00:00:00 2001
From: Tom Butterworth <bangnoise@gmail.com>
Date: Tue, 15 Aug 2017 13:40:20 +0100
Subject: [PATCH] Throttle calls to EdsOpenSession

Together with 09acf9bfd1470f745265cd122471ace25a17c795 this fixes #8
---
 Camera Live/SyPCanonDSLR.h | 1 +
 Camera Live/SyPCanonDSLR.m | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/Camera Live/SyPCanonDSLR.h b/Camera Live/SyPCanonDSLR.h
index eb06e36..1f2330e 100644
--- a/Camera Live/SyPCanonDSLR.h	
+++ b/Camera Live/SyPCanonDSLR.h	
@@ -50,5 +50,6 @@
     SyPCanonEVFImageBuffer *_nextImage;
     SyPImageBuffer *_pendingImage;
     NSError *_pendingError;
+    NSTimeInterval _lastSession;
 }
 @end
diff --git a/Camera Live/SyPCanonDSLR.m b/Camera Live/SyPCanonDSLR.m
index 320612e..2509e73 100644
--- a/Camera Live/SyPCanonDSLR.m	
+++ b/Camera Live/SyPCanonDSLR.m	
@@ -464,7 +464,14 @@ - (NSError *)startSessionOnQueue
         if (OSAtomicCompareAndSwapPtrBarrier(NULL, self, (void **)&mSession))
         {
             _hasSession = YES;
+            // Throttle sessions or the EdsOpenSession call never returns
+            NSTimeInterval since = [NSDate timeIntervalSinceReferenceDate] - _lastSession;
+            if (since < 0.5)
+            {
+                usleep((0.5 - since) * USEC_PER_SEC);
+            }
             EdsError result = EdsOpenSession(_camera);
+            _lastSession = [NSDate timeIntervalSinceReferenceDate];
             error = [SyPCanonDSLR errorForEDSError:result];
         }
         else