I just figured out that this bug goes away if I rename the file to something that doesn't use the colon character.  I'm going to guess that the root cause is the same as this bug:

https://bugs.kde.org/show_bug.cgi?id=407778#c16

Special character in the file name like \/ ? : * " <> ¦ are not possible under Windows. Please avoid these characters. 

I close this bug as "works for me".

If it still appears in the latest version, please feel free to re-open it and update the affected version number.

Hi, This bug can be reproduced on Linux, not on Windows.

I presume that Linux is a supported platform for Kdenlive, is it not?  If special characters like ':' are not supported in Kdenlive for any platform, then should it not prompted the user with error messages so they can take some corrective action instead of producing silently corrupted output?  Otherwise, users will never know that they need to avoid these characters and simply assume that Kdenlive doesn't work.

I had something in mind that this was fixed but couldn’t find the commit. 

Tested with a file name contains a colon (rend:der.mp4) with daily build #255 (https://binary-factory.kde.org/job/Kdenlive_Nightly_Appimage_Build/lastSuccessfulBuild/artifact/). Change the speed (by holding CTRL and pull the end of the clip). It plays and it renders correct. Could you test as well?

Created attachment 121947 [details]
INVALID

Hi, I re-tested this with:

md5sum kdenlive-19.11.80-c8f28bb-x86_64.appimage 
68535739219c73c1b55ed6b3ca369273  kdenlive-19.11.80-c8f28bb-x86_64.appimage

Using these steps:

mkdir /tmp/speed
cd /tmp/speed
wget https://binary-factory.kde.org/job/Kdenlive_Nightly_Appimage_Build/lastSuccessfulBuild/artifact/kdenlive-19.11.80-c8f28bb-x86_64.appimage
md5sum 
chmod u+x kdenlive-19.11.80-c8f28bb-x86_64.appimage
wget "http://www.robertelder.ca/Screencast 2019-06-08 13:53:57.mp4"
/tmp/speed/kdenlive-19.11.80-c8f28bb-x86_64.appimage

1)  Added "Screencast 2019-06-08 13:53:57.mp4" and used right-click, change speed effect to set speed to 200. Rendered to out.mp4. Result:  Still produces a file that just rendered to white output.

2)  Added "Screencast 2019-06-08 13:53:57.mp4" and used ctrl drag method to change speed.  Rendered to out2.mp4.  Result:  Still produces a file that just rendered to white output.

3)  Change the clip to ren:der.mp4, then add and use ctrl drag method to change speed.  Rendered to out3.mp4.  Result:  Produced a video that consists of black with white text that says "INVALID".  See attached.

Thanks for reporting. Confirmed. I tested with your file and get the same wrong results. I opened issue https://invent.kde.org/kde/kdenlive/issues/315

*** Bug 411412 has been marked as a duplicate of this bug. ***

I just tested this bug out again using the following steps and it appears to be fixed in version kdenlive-19.12.0a-x86_64.appimage:

mkdir /tmp/speed
cd /tmp/speed
wget http://mirrors.ocf.berkeley.edu/kde-applicationdata/kdenlive/release/kdenlive-19.12.0a-x86_64.appimage
md5sum -c <(echo "1d12febea853500fb1e0f1adeeea4f32  kdenlive-19.12.0a-x86_64.appimage")
chmod u+x kdenlive-19.12.0a-x86_64.appimage
wget "http://www.robertelder.ca/Screencast 2019-06-08 13:53:57.mp4"
/tmp/speed/kdenlive-19.12.0a-x86_64.appimage
#  Now add the clip 'Screencast 2019-06-08 13:53:57.mp4' to timeline.  Right-click on clip and select change speed.  Change speed to 200 using right-click method.  Then render project to /tmp/speed/untitled.mp4

Also tested with re-naming the clip to ren:der.mp4 and adding that to the project.  Renders just fine in both cases.

I now consider this bug fixed since I no longer see any issues with my test case.  I am going to go ahead and mark this bug as resolved (let me know if you'd rather update the bug statuses yourselves).

Thank you for the feedback and contribution. Glad to hear it works.