OpenCV's ffmpg dll causing access violation

I previously successfully modified the example face tracking code from IntraFace (<http://www.humansensing.cs.cmu.edu/intraface/download_functions_matlab.html>) to work with a web cam, creating one version that shows the video and tracking points ant another that just displays pose angles. I now want to try feeding the function a video, but both functions result in an "Access Violation" crash:

    -----------------------------------------------------------------------
              Access violation detected at Mon Sep 14 10:50:24 2015
    ------------------------------------------------------------------------

    Configuration:
      Crash Decoding      : Disabled
      Crash Mode          : continue (default)
      Current Graphics Driver: Unknown hardware 
      Default Encoding    : windows-1252
      Graphics card 1     : Intel Corporation ( 0x8086 ) Intel(R) HD Graphics 4600 Version 10.18.10.3412
      Host Name           : CSE050
      MATLAB Architecture : win64
      MATLAB Root         : C:\Program Files\MATLAB\R2015a
      MATLAB Version      : 8.5.0.197613 (R2015a)
      OpenGL              : hardware
      Operating System    : Microsoft Windows 7 Enterprise 
      Processor ID        : x86 Family 6 Model 60 Stepping 3, GenuineIntel
      Virtual Machine     : Java 1.7.0_60-b19 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
      Window System       : Version 6.1 (Build 7601: Service Pack 1)

    Fault Count: 1

    Abnormal termination:
    Access violation

    Register State (from fault):
      RAX = 0000000006bf1410  RBX = 00000000769afd80
      RCX = 0000000006bf1410  RDX = 0000000000000009
      RSP = 0000000004023540  RBP = 0000000006bf0b70
      RSI = 0000000006bf2410  RDI = 0000000000000004

       R8 = 00000000f74f3090   R9 = 00000000f74f1fa0
      R10 = 0000000006bf4240  R11 = 0000000006b768c0
      R12 = 0000000006b770c0  R13 = 0000000000000004
      R14 = 0000000000000184  R15 = 00000000f7aaa460

      RIP = 00000000f74f2030  EFL = 00010206

       CS = 0033   FS = 0053   GS = 002b

    Stack Trace (from fault):
    [  0] 0x00000000f74f2030 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05906480 read_InputMediaStream_FFMPEG+05890656
    [  1] 0x00000000f74f2175 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05906805 read_InputMediaStream_FFMPEG+05890981
    [  2] 0x00000000f74f2fd5 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05910485 read_InputMediaStream_FFMPEG+05894661
    [  3] 0x00000000f74f3015 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05910549 read_InputMediaStream_FFMPEG+05894725
    [  4] 0x00000000f74f3055 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05910613 read_InputMediaStream_FFMPEG+05894789
    [  5] 0x00000000f74f3095 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05910677 read_InputMediaStream_FFMPEG+05894853
    [  6] 0x00000000f74f4f36 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+05918518 read_InputMediaStream_FFMPEG+05902694
    [  7] 0x00000000f7aaa460 C:\Users\...\FacialFeatureDetection&Tracking_v1.1\opencv_ffmpeg244_64.dll+11904096 read_InputMediaStream_FFMPEG+11888272
    [  8] 0x0000000006bf1410                                   <unknown-module>+00000000
    [  9] 0x00000000769b2240                                   <unknown-module>+00000000

    This error was detected while a MEX-file was running. If the MEX-file
    is not an official MathWorks function, please examine its source code
    for errors. Please consult the External Interfaces Guide for information
    on debugging MEX-files.

I'm not sure if this is due to Matlab or OpenCV. Any ideas?