How Changing Video Frame Rate Affects File Size

Posted on by Larry

Last week, I wrote about the challenges 8K video presents to our storage systems. More generally, though, that article was about how storage bandwidth and capacity increase as frame size increases. This week, I want to look at the effect increasing video frame rates has on storage capacity and bandwidth.

NOTE: In this example, I’m using Apple ProRes as a baseline codec. Other codecs will generate different numbers, but the basic results are the same. Here’s a white paper from Apple with all the source numbers.

EXECUTIVE SUMMARY

Regardless of frame size, as frame rates increase, storage needs and bandwidth also increase. If we set the storage needs of 24 fps video (regardless of frame size) to 100%, then:

Just as capacity increases by these amounts, so, also, does bandwidth. Higher frame rates require bigger and faster storage.

THE CHARTS

This is the key chart that illustrates the numbers outlined in the Executive Summary. If we set 24 fps media to 100% capacity and bandwidth, note how increasing the frame rate increases both the capacity required to store the media and the speed of the storage bandwidth to support the increased frame rate.

NOTE: What about audio? Well, an hour of uncompressed 16-bit audio is 650 MB. While not a small file, this pales into insignificance when compared to the gigabytes per hour that video requires.

The next three charts illustrate, based on Apple’s research, the capacity changes for 1080p, UHD, and 8K media as frame rates change.


(Storage capacity required to store one hour of 1080p media.)


(Storage capacity required to store one hour of UHD media.)


(Storage capacity required to store one hour of 8K media.)

Notice that in all three charts, the shape of the curve is the same, only the amount of data being transferred changes. For example, 60 fps 1080p ProRes 422 requires 132 GB to store per hours while 60 fps 8K ProRes 4444 requires 5,091 GB!

NOTE: While many high-end productions are now shooting HDR material at bit-depths up to 16-bit, the general relationship of frame rate to storage remains the same, though the specific numbers will vary by frame size and codec.

SUMMARY

When working with HD media, it is easy to assume that our storage can easily handle different frame rates – and it can, because the amount of data being transferred each second is relatively small at small frame sizes.

However, changing frame sizes require a close examination of our storage as frame rates also increase.


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