cvtColor RGB to GRAY end up in a shorter video with nine tiles instead of one

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I am new to opencv and python and not really sure ehere to address this issue... When I gray-scale a mp4 teststream I end up with a grayed video but it is shorter than the original and i see it multiple (9) times in the viewing frame.

To test my code I used cv2.COLOR_RGB2YUV and that woked fine

This works fine 10 sec.video as one image in the viewing frame

new_clip = test_clip.fl_image(lambda x: cv2.cvtColor(x, cv2.COLOR_RGB2YUV))

This fails only 3 sec. output and 9 tiles of the same content in the viewing frame

new_clip = test_clip.fl_image(lambda x: cv2.cvtColor(x, cv2.COLOR_RGB2GRAY))

Best regards NIls

tested in miniconda jupyter notebook: bleach 1.5.0 py36_0
cycler 0.10.0 py36_0
dbus 1.10.10 0
decorator 4.0.11 py36_0
entrypoints 0.2.2 py36_1
expat 2.1.0 0
fontconfig 2.12.1 3
freetype 2.5.5 2
glib 2.50.2 1
gst-plugins-base 1.8.0 0
gstreamer 1.8.0 0
hdf5 1.8.17 1
html5lib 0.999 py36_0
icu 54.1 0
imageio 2.1.2 py36_0 conda-forge ipykernel 4.6.1 py36_0
ipython 6.0.0 py36_0
ipython_genutils 0.2.0 py36_0
ipywidgets 6.0.0 py36_0
jbig 2.1 0
jinja2 2.9.6 py36_0
jpeg 8d 2
jsonschema 2.6.0 py36_0
jupyter 1.0.0 py36_3
jupyter_client 5.0.1 py36_0
jupyter_console 5.1.0 py36_0
jupyter_core 4.3.0 py36_0
libffi 3.2.1 1
libgcc 5.2.0 0
libiconv 1.14 0
libpng 1.6.27 0
libprotobuf 3.2.0 0
libsodium 1.0.10 0
libtiff 4.0.6 2
libxcb 1.12 1
libxml2 2.9.4 0
markupsafe 0.23 py36_2
matplotlib 2.0.0 np112py36_0
mistune 0.7.4 py36_0
mkl 2017.0.1 0
moviepy 0.2.3.2 <pip> nbconvert 5.1.1 py36_0
nbformat 4.3.0 py36_0
notebook 5.0.0 py36_0
numpy 1.12.1 py36_0
olefile 0.44 py36_0
opencv 3.1.0 np112py36_1
openssl 1.0.2k 1
pandocfilters 1.4.1 py36_0
path.py 10.3.1 py36_0
pcre 8.39 1
pexpect 4.2.1 py36_0
pickleshare 0.7.4 py36_0
pillow 3.4.2 py36_0
pip 9.0.1 py36_1
prompt_toolkit 1.0.14 py36_0
protobuf 3.2.0 py36_0
ptyprocess 0.5.1 py36_0
pygments 2.2.0 py36_0
pyparsing 2.1.4 py36_0
pyqt 5.6.0 py36_2
python 3.6.1 0
python-dateutil 2.6.0 py36_0
pytz 2017.2 py36_0
pyzmq 16.0.2 py36_0
qt 5.6.2 2
qtconsole 4.3.0 py36_0
readline 6.2 2
setuptools 27.2.0 py36_0
simplegeneric 0.8.1 py36_1
sip 4.18 py36_0
six 1.10.0 py36_0
sqlite 3.13.0 0
tensorflow 1.0.1 np112py36_0
terminado 0.6 py36_0
testpath 0.3 py36_0
tk 8.5.18 0
tornado 4.5.1 py36_0
tqdm 4.11.2 <pip ...











































































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