Scrubbing Lag.

Question

When Scrubbing on the timeline or any of the monitors, the higher the resolution the "choppier" it gets to scrub.

However, some higher resolution formats (i.e 4k Arri mov) perform much better that lower resolution formats (i.e 1080 Canon mp4)

Of course scrubbing is silky smooth when the timeline is rendered. Changing the resolution on the program monitor from full to 1/4 does not affect how smooth is it to scrub, only the resolution when scrubbing. Scrubbing also is smooth if a specific video have been scrubbed/played before.

(i.e if I scrub a 4k video freshly imported to the timeline, it scrubs with an awful lag. If I play the video from beginning to end, and then try to scrub it, it scrubs smooth)

Files natively compressed with Prores don't have any issue. The issue here is mainly with h.264

So in order to achieve smooth scrubbing under any circumstance, and to avoid people who just spend time on forums because they are bored, Please answer the following questions if you have a solid answer.

1) When ONLY playing a video in premiere, what happens in the background. we know that importing, creates peak files and conformed files. what does playback or scrubbing do?

2) Is there a way to force whatever happens in the background during playback without actually playing?

3) Nothing, in any setting around premiere affects the smoothness of playback or scrubbing. Am I missing something?

4) File format/compression seems to be a major factor regardless of the resolution

iMac (Retina 5K, 27-inch, 2017)

4.2 GHz i7

64gb 2400 MHz

Radeon Pro 580 8gb

R Neil Haugen · Accepted Answer

It's pure physics or math if you prefer.

The files you're having trouble with are long-GOP, which is a codec type that works great with a specially designed chip in the camera to reduce a LOT of data to something recordable on the card ... fast. It is NOT designed to edit worth a crap.

There's only a "real" complete (though heavily compressed) " I " frame every 9-30 "recorded" frames. In-between are "p" and "b" frames, which aren't frames at all. They're a data-set of only the pixels that have or will change from the last I frame or the next one ... or both. The computer has to de-encode an I frame, pass along, store to RAM, call up the next p/b frame, recall the I frame from RAM, compute that frame ... pass it along, store to RAM, call up the next p/b dataset, recall ... rinse & repeat.

FAR more work than simply de-encoding complete frames, even "large" many-K frames.

ProRes, Cineform, and DNxHD/R are codecs designed for editing. Every frame is a complete frame and simply compressed in a format designed for fast de-encoding.

So there isn't something weird going on in the program, and your questions there don't really matter at all.

It's the codec you're working with. Which is why you may very well need proxies to get smooth playback when dealing with H.264 1080p, but work some 6k ProRes or DNxHR without trouble.

And when making proxies, do NOT use the included H.264 preset, I've no clue why anyone would want that. Use the Cineform ones ... they will playback smoothly and fast.

Neil

Amuthan007 · Answer

You certainly have a point. But what I don't understand is, MacBook Pros that were released after 2018 comes with the T2 chip that can encode and decode H.264. But I'm having the issue with H.264 in a Mov container. I should not be having this issue. ProRes is a native Apple codec and it'll be fast anyway. But H.264 should be smooth on Macs that carry a T2 chip. I can see that the T2 chip is working because the machine doesn't heat up much or fans don't go into full blast when working on full blast when I work with H.264 files. But the Scrubbing Lag is frustrating. Not allowing me to have a smooth flow of work.

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