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frame size on file size

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Luke Durack
frame size on file size
on Feb 11, 2008 at 2:53:26 am

Hi folks,
Ive never been quite clear on this one. Does frame size affect file size. Ive done a series of tests with the same footage at different frame sizes and the file size seems to always be the same. Is this correct?
Many thanks.
Luke.



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Daniel Low
Re: frame size on file size
on Feb 11, 2008 at 10:38:30 am

Yes it is correct, as long as you didn't alter the bitrate.

On a very basic level:

Part of transcoding is usually defining a bitrate, say for example 500Kb/s. This works out to be 20Kb per frame (@ 25fps).

Obviously the larger the frame the less bits there are to store information on a 'pixel' by 'pixel' basis, so if you increase the frame size and don't increase the bitrate the image will degrade.

As such, the rule of thumb is generally considered to be that larger frame sizes require higher bitrates to meet a certain quality level.


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Luke Durack
Re: frame size on file size
on Feb 11, 2008 at 11:44:46 am

Hi Daniel,
Thanks very much for that. Good to finally have that clear.
Thanks again.
Luke.





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