possible bug in `qtdemx` element

[David Ing]

I have a video file (no audio) which plays nicely in

   - VLC
   - Windows Media Player on Windows 10
   - Whatever application plays videos by default in Windows 10

The video is here:

https://drive.google.com/file/d/1EJj8Ydb5khkQAxCtbjZ0piZPk93Lwwz8/view?usp=sharing

I have analyzed the video with `ffprobe` (in many ways) and I cannot find
any problems with it.

The problem is: *qtdemux* doesn't play nicely with the video; and so I
cannot use GES with the video (which is my ultimate goal).

The problem apparently exists in Gstreamer 1.14.4 and 1.16.0 (these are the
two versions I tested).

The problem is easily reproduced using `gst-launch` commands.

# ------------------------
# Gstreamer 1.14.4 (mingw windows)
# ------------------------
$ *gst-launch-1.0 filesrc location=screencap.mp4 ! decodebin ! playsink*
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Redistribute latency...
Redistribute latency...
ERROR: from element
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstQTDemux:qtdemux0:
Internal data stream error.
Additional debug info:
qtdemux.c(6073): gst_qtdemux_loop ():
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstQTDemux:qtdemux0:
streaming stopped, reason not-negotiated (-4)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...

# ------------------------
# Gstreamer 1.16.0 (mingw windows)
# ------------------------
$ *gst-launch-1.0 filesrc location=screencap.mp4 ! decodebin ! playsink*
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Redistribute latency...
Redistribute latency...
WARNING: no real random source present!
ERROR: from element
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstQTDemux:qtdemux0:
Internal data stream error.
Additional debug info:
../gst/isomp4/qtdemux.c(6607): gst_qtdemux_loop ():
/GstPipeline:pipeline0/GstDecodeBin:decodebin0/GstQTDemux:qtdemux0:
streaming stopped, reason not-negotiated (-4)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...
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