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MP4 vs Prores: worth the size difference?

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Olivier Prudhomme
MP4 vs Prores: worth the size difference?
on May 9, 2018 at 6:06:52 pm

I have 4K footage from a Pixel Phone, MP4
I converted to Prores and as expected the files are around 10 times bigger - Data rate diff.

However once in premiere I can not see the difference in quality...
Is there a good reason to edit with the huge Prores files?


Los Angeles - TV Promo Editor - FCP - AVID

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John Heiser
Re: MP4 vs Prores: worth the size difference?
on May 9, 2018 at 7:31:18 pm

You won't see any difference in quality. What you will see is better performance from your computer.

MP4s (h.264) are "long-GOP" files and require more computation to play back and edit; the GOP (Group Of Pictures) consists of a full video frame followed by several delta frames, which represent the differences between that frame and the initial frame, making editing more complicated for the processor. ProRes files are "I-frame," meaning every frame is individually compressed; this makes playback and editing less complicated for the computer.

The other thing you might gain is less artifacting as you apply heavier effects, such as color grading. ProRes is a 10-bit codec, so it won't fall apart quite so soon. Now, your 8-bit MP4s are still limited in the amount of color information that they hold, so expect some blocking on heavy color adjustments and such.

But the primary benefit of transcoding to ProRes (or DNx) is I-frame performance. This is especially important if you're working in UHD or 4k, since those files are "heavier" right out of the gate. In that case, use Premiere's proxy workflow to transcode to ProRes Proxy or ProRes LT for editing. All your exports will still be from the original material (unless it's offline).

John Heiser
Senior Editor
o2 ideas

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Dave LaRonde
Re: MP4 vs Prores: worth the size difference?
on May 9, 2018 at 10:18:42 pm

I hope you used one of those apps that make a phone camera behave like a real video camera! Don't shoot without using it!

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA

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