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Why Does Compressing a Video for Vimeo In FCP Double the File Size?

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Paul Pikarsky
Why Does Compressing a Video for Vimeo In FCP Double the File Size?
on Oct 7, 2013 at 3:29:21 pm

Hello All,

We're finishing up a 3:35 corporate web video in Final Cut Pro 7.

Working in FCP we normally make a 1280x720 viewing file using "automatic" instead of restricting the compression. That file was about 180MB.

We're now following Vimeo's guidelines for compression restricting the video to 7000 Kbits a second and the audio to ..

When I export the restricted compression for internet streaming, it comes out to be about 351mb.

Why is the file doubling in size when it should be compressing smaller for the internet?
Is this standard in a situation where you restrict the kbits/sec and change the audio to AAC?

Am I doing something wrong in the process that is making my video bigger as opposed to a smaller file size?

Thanks for your time!

Paul


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Ivan Myles
Re: Why Does Compressing a Video for Vimeo In FCP Double the File Size?
on Oct 7, 2013 at 6:26:52 pm

In general, the file is encoded to meet the target bitrate. Based on the file sizes it sounds like your Vimeo setting is about twice the automatic setting. Note that the recommended Vimeo bitrate is for submitting the file prior to recompression. The final Vimeo bitrate is about 2500 kbps for a 1280x720 file.

I am having trouble with the math using the numbers in your post. The bitrate for the automatic setting can be calculated as follows:

Bitrate = File Size / Duration
= (180MB) / (215s) x (8 b/B) x (1024 kb/Mb)
= 6858 kbps

This seems high for a 1280x720 automatic setting. What is the frame rate?

The encoded bitrate using the Vimeo setting is as follows:

(351MB) / (215s) x (8 b/B) x (1024 kb/Mb) = 13,374 kbps

This is much higher than 7000 kbps.

Please confirm the file sizes and length of video. If the numbers in the original post are correct, please take screen shots of the export panel with the automatic and Vimeo settings.


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