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User profile for user: teacher24_70
teacher24_70 Author
User level: Level 2
292 points

Trim commercials from mp4 files without re-encoding

I used Elgato Video Capture hardware/software to transfer a VHS (TV movie recording) to my Mac. It created a file 1.45 GB that included commercials. According to Elgato's documentation (I know it's old) I can trim commercials in iMovie without having to re-encode it. I was easily able to trim out the commercials but was then forced to "export" the file (which seemed to re-encode) and resulted in an 8 GB file--more than 4 times the original file size.


I've read documentation that iMovie (current version 10.3.3) HAS to encode, so the Elgato documentation must have been for a MUCH older version of iMovie that dealt with files in a different way. I've also read that I can use Quicktime 7 to trim and save without re-encoding, but it doesn't seem that QT7 is compatible with Big Sur so I'm not even sure it's worth trying to find and download.


Does anyone know another way of trimming out the commercials without resulting in a file that is 4 times larger than the original?

MacBook Pro 13″, macOS 11.6

Posted on Aug 24, 2022 11:32 PM

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User profile for user: Rich839
Rich839
User level: Level 8
47,844 points

Posted on Aug 25, 2022 9:28 AM

Your download of the commercial movie may be a violation of the copyright laws. Assuming that it is not:


Yes, iMovie would need to re-encode in order to embed the deletions of the commercials.


Check your iMovie export settings. Rather than alter the resolution, you can reduce the size by adjusting the Quality settings to High, Medium, or low, or choosing the Custom quality and using the slider to reduce the Mbps value. Avoid using the Best Quality (pro res) settings, because that will give you a very large .mov file, about 4x the size of the other settings.


Another way to reduce the file size of an exported project is to export it to Email. In the export box you will have resolution options of Small, Medium, or Large. Select the one you want and export. After the export is finished, an email template will appear with the icon of the exported movie contained in the body of the email. Drag the icon out to your desktop (don't send the email). Then see if the movie plays in the size and quality that you want.


-- Rich





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User profile for user: Rich839
Rich839
User level: Level 8
47,844 points

Aug 25, 2022 9:28 AM in response to teacher24_70

Your download of the commercial movie may be a violation of the copyright laws. Assuming that it is not:


Yes, iMovie would need to re-encode in order to embed the deletions of the commercials.


Check your iMovie export settings. Rather than alter the resolution, you can reduce the size by adjusting the Quality settings to High, Medium, or low, or choosing the Custom quality and using the slider to reduce the Mbps value. Avoid using the Best Quality (pro res) settings, because that will give you a very large .mov file, about 4x the size of the other settings.


Another way to reduce the file size of an exported project is to export it to Email. In the export box you will have resolution options of Small, Medium, or Large. Select the one you want and export. After the export is finished, an email template will appear with the icon of the exported movie contained in the body of the email. Drag the icon out to your desktop (don't send the email). Then see if the movie plays in the size and quality that you want.


-- Rich





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Trim commercials from mp4 files without re-encoding

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