Why does VideoReader not load a video, inspite of GStreamer availability?

    >> VideoReader.getFileFormats()
Video File Formats:
    .avi - AVI File
    .mj2 - Motion JPEG2000
    .ogg - OGG File
    .ogv - OGG Video
>> file_name = 'trial.avi';
>> myfile = VideoReader(file_name);
Error using VideoReader/init (line 611)
Failed to initialize internal resources.
Error in VideoReader (line 176)
            obj.init(fileName);

I get the above Error when trying to read a video file. Tried .avi, .mp4 and .MOV.

OS - Debian Stretch 9 Matlab version - 2018b Gstreamer - 1.0 (latest)