I don't know if this can help, but because there is a new version of K-lite codec (14.30), I think it could.
You can refer to a previous old topic: https://forum.videohelp.com/threads/351832-Subtitle-Workshop-MP4-MKV-video-preview-problem
Now, when finishing the installation of the K-lite codec, you must tick "Run codec tweak tool"
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You have now two options (maybe take both, I don't know).
1rst option, click on DirectShow Filters under Configuration:
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Then click on ffdshow video decoder
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Go at the bottom of the right
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Click on disabled to make the radio button appear, and choose either "all RGB"
![]()
either YV12
![]()
I don't know which one works, just try. You can install and install K-lite codec as often as you need.
2nd option:
Under Codec and Filter management, click DirectShow x64
![]()
Now click ffdshow videodecoder
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And finally tick ffdhowRAW video processor
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I guess now you can read mkv and mp4 videos with Subtitle Workshop 6.0
Now, I have a question: is it possible to read .vob videos with SW?
You can refer to a previous old topic: https://forum.videohelp.com/threads/351832-Subtitle-Workshop-MP4-MKV-video-preview-problem
Now, when finishing the installation of the K-lite codec, you must tick "Run codec tweak tool"

You have now two options (maybe take both, I don't know).
1rst option, click on DirectShow Filters under Configuration:

Then click on ffdshow video decoder

Go at the bottom of the right

Click on disabled to make the radio button appear, and choose either "all RGB"

either YV12

I don't know which one works, just try. You can install and install K-lite codec as often as you need.
2nd option:
Under Codec and Filter management, click DirectShow x64

Now click ffdshow videodecoder

And finally tick ffdhowRAW video processor

I guess now you can read mkv and mp4 videos with Subtitle Workshop 6.0
Now, I have a question: is it possible to read .vob videos with SW?