From 35a2f2fef911af0cd0eafd855754ea6e5ce2da90 Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.alekhin@intel.com>
Date: Sat, 24 Jun 2017 11:07:57 +0300
Subject: [PATCH] videoio(macosx): fix array access exception in AVFoundation

---
 modules/videoio/src/cap_avfoundation_mac.mm | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/modules/videoio/src/cap_avfoundation_mac.mm b/modules/videoio/src/cap_avfoundation_mac.mm
index 07aac1af9c..0ef461c8a9 100644
--- a/modules/videoio/src/cap_avfoundation_mac.mm
+++ b/modules/videoio/src/cap_avfoundation_mac.mm
@@ -694,7 +694,15 @@ CvCaptureFile::CvCaptureFile(const char* filename) {
         return;
     }
 
-    mAssetTrack = [[mAsset tracksWithMediaType: AVMediaTypeVideo][0] retain];
+    NSArray *tracks = [mAsset tracksWithMediaType:AVMediaTypeVideo];
+    if ([tracks count] == 0) {
+        fprintf(stderr, "OpenCV: Couldn't read video stream from file \"%s\"\n", filename);
+        [localpool drain];
+        started = 0;
+        return;
+    }
+
+    mAssetTrack = [tracks[0] retain];
 
     if ( ! setupReadingAt(kCMTimeZero) ) {
         fprintf(stderr, "OpenCV: Couldn't read movie file \"%s\"\n", filename);