I found out what went wrong with my earlier video. I had the “use hardware encoder” box checked. When I un-checked it, the problem went away.
WHY WAS THIS SO DIFFICULT TO FIND?
Because I was mis-led by something that boils down to (maybe) a cultural artifact of some kind?? There is a “detect hardware encoder” option next to the “use hardware encoder” box and this is usually explained in the “manual” in the following way:
Run the “detect hardware encoder” and see if you have a hardware encoder. If you do, check the box marked “use hardware encoder” to activate it.
This is a bit weasley. It implies that if you have some kind of hardware encoder, then you will have no problem using it if it’s detected. But this isn’t true. Shotcut detects a “hardware encoder” on my laptop but when I use it it fouls up the video. So just “having it” isn’t enough. Shotcut can DETECT it, but it can’t tell you if it will work or not.
SO THE SOFTWARE SEEMS TO ENCOURAGE YOU TO SWITCH ON SOMETHING THAT MIGHT FAIL?
Yes. In an airplane, your butt would be scattered over several counties due to something like this. Telling me to “go on ahead and let ‘er rip” is dumb. Having a detector that can “find” an option does not imply that it will work. Shotcut should tell me that enabling it may or may not work. The correct procedure should be:
Check hardware for correct operation.
If hardware is not available, OR if it fails the ops check, disable it.
Shotcut does not tell me, the ignorant noob, that enabling this may foul up my videos. It implies that if it “detects” hardware acceleration, then it’s “good to go.” This is not true. You have to test it to make sure it works, but with the way it’s presented it seems as if that would be the LAST thing to cause a problem– when it should be the first thing suspected because it was never tested before it was deployed. By me. I’m saying I “deployed” it. Me.
So that’s my story and I’m sticking to it.