File size conversion question

[Techno]

Working on the theory that there are no stupid questions......

I have taken some footage with my GoPro HD. When I transfer it from the card it is in MPEG4. If I use MPEG Streamclip to convert it to Quicktime, it grows in size. For example, a 500MB clip becomes about 14GB.

Is that because the MPEG4 format is so highly compressed? Can someone offer an insight into why the clip is so much bigger after conversion and what the benefits are, apart from apparently being easier to edit.

 

[DirtyPicturesTV]

GoPro shoots in H.264, so yes, it's more compressed than, for example, an intermediary format like ProRes.

Quicktime is a container, not a format, so calling your file Quicktime is meaningless.

But if your conversion is increasing the file size so much, you may be defaulting to something with a data rate far beyond what you need to work with. You can, for example, tweak your Streamclip settings and play with lowering the data rate to get a smaller file.

Here's what I would do:

In Streamclip, with a raw GoPro H.264 file open, choose File > Export to Other Formats.

Now hit the Options button to have control over your export settings.

This Export to Other Formats setting gives you greater control than just the basic Quicktime option, and you can still export using the Quicktime container with any video format you want (I suggest ProRes 422 or 422 (HQ) if you have not already done so). In fact, Streamclip simply opens the Quicktime encoding engine just like you see when exporting in FCP.

If your files are still too big, try lowering the Compression Quality or Data Rate (under that same Options button, hit Settings); then do some test exports to check quality.