"This file does not support seeking"

I’m fairly new to shotcut and video editing as a whole but I’ve sunk a couple dozen hours into shotcut so far and this is the first time seeing this error.
I dropped a normal MP4 into shotcut but it now says it cant use it and it is non-seekable. The weird thing is, i recorded it the same way I recorded everything else that i’ve edited on shotcut.
Background:
I’m editing a gameplay video and my recording software likes to split a whole recording into smaller recordings so I end up with a few MP4’s to deal with. It’s never been an issue before, I just drag them all in and stitch them together and they work. However, halfway through editing this video, I dragged the 3rd/4th chunk of the video and every subsequent chunk shows the same error. They’re all the exact same MP4 format, exactly the same details and everything. Anyone have any idea what I can do to fix this? Converting them into “editing friendly” bugs out the recording significantly, making it very choppy.

That is your only option.

making it very choppy.

Use preview scaling and proxy.

ok, thank you.
Do you have any idea why this problem occurred? Like I said, it happened randomly part way through a recording? Would it be a problem with my recording software?
(essentially, what causes an MP4 to become non-seeking so I can prevent it from happening.)

The recording software switched to variable frame rate. It might do this if the computer can’t keep up the normal frame rate due to too much stuff running at once. It could also be that all the files are variable frame rate, but the first three were so steady that they weren’t detected as VFR.

I’m not so sure. Sometimes i will import a file and it will say that it is a variable framerate but it’s no problem, i just use it anyways. These MP4’s are different for some other reason.

You just confirmed my suspicion. When all is well, the rate is steady enough to not be a problem. If you start up Crysis in the background, recording starts to lag. :sweat_smile:

no no, there wasnt a variable framerate for this file. My point was that when i do have files with a variable framerate, I can still use it however this is a different problem entirely.

Unless the entire file has passed a vfrdet test with ffmpeg (or some similar process), this claim cannot be verified or relied upon. Shotcut only checks a small sample at the beginning of the file for speed reasons. Inconsistent time stamps could occur later in the file and cause problems.

If the video is coming from a screen recorder that isn’t specifically set for CFR, then we should assume it’s VFR. Another possibility is if a screen recorder set for CFR lags under heavy load and produces a file that isn’t smooth.

More accurately, you are sometimes getting lucky. This is not an officially supported or recommended workflow. It all depends on how steady the VFR is. If VFR is in the mix, conversion to Edit Friendly is the only real fix. If the converted file is choppy in a media player, then the screen recorder is making a bad file. If the converted file is choppy only in Shotcut, use proxy and preview scaling.

Without knowing what screen recorder you’re using and it’s settings, it’s hard to diagnose further. But the problem is definitely coming from there. It might also be a fragmented MP4 issue. If so, then maybe saving files as Matroska (MKV) instead of MP4 might be a solution.

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