Aspect ratio conversions cause huge rendering times

I have source videos that are 30 seconds or so in length and in 16:9 aspect ratio. If I export those without changing aspect ratios (even with fancy filters), the export only takes a few minutes. However, if convert those into 9:16 aspect ratio (required for youtube shorts), the same exact clip will take a few hours to export, even with hardware encoding enabled. My friend uses wondershare for this same process and only needs a few minutes for the same export and also has live previews without lowering quality. Am I missing some steps, or does shotcut just need this long to convert aspect ratios?

For reference, I have the project in 9:16, one main track for the scaled/cropped source video (which is 16:9), and one blurred background track based off the source video to fill out the top and bottom instead of having black bars there.


If this is turned off, what is the rendering time? Is it perhaps the blur filter taking a long time to process?

In addition to @Austin’s question…

Have you tried to enable “Parallel Processing” in the advanced section of the export tab?

It seems like the processing time is about the same unless I don’t have an aspect ratio conversion happening. Thanks.

That’s enabled already. Thanks.

I am also curious about this. In my experience, aspect ratio conversion is not particularly time consuming. But blur often is. Have you tried disabling filters one-by-one to see if one of your filters is causing the slow export?

You could give the Blur:pad filter a shot, it sounds like it’s exactly what you want and might be more efficient.

It does seem to be all about the blur filter. Thanks for the suggestions. I was using gaussian blur which makes a 4 minute export run for almost 3 hours… I’m testing with some of the other blur implementations. So far, they all seem significantly faster.


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