Question About Previews

[ShaunK321]

I've been using Premiere Pro for over 15 years at this point, but I've never had great success with Preview files actually speeding up rendering. A couple years ago someone told me to switch my Previews codec to GoPro CineForm (YUV 10-bit) and then the final render would go faster if I used previews. That did seem to sometimes make a difference when exporting h.264 files.

Right now, I have a long video (2.5 hrs) that has lots of clips with Neat Video's Reduce Noise v5.1.0 plugin applied. These are 10-bit 4K clips from a Panasonic Lumix GH5 and Reduce Noise typically takes a while to render, so I rendered the entire timeline overnight to save myself time in the long run since I have to render it out for web, Blu-ray, and DVD. When I go to render out the timeline that now is showing all green across the whole thing, I choose "Use Previews" and I don't select "Use Maximum Render Quality", I notice that when it gets to the clips with the Reduce Noise effect, it's taking just as long to render those clips as it did to render the preview files. So, basically, it's re-rendering all of the clips with Reduce Noise on them that I've already rendered as previews. 

What am I doing wrong?

System Specs:

Windows 10 64-bit

64GB Ram

AMD Ryzen 3900X 12-core

RTX 2060

NVME 2TB system drive

NVME 1TB project drive 

[Christian.Z]

@Kevin-Monahan would be able to give the best insight on this.

[R Neil Haugen]

There's two ways to approach this.

The first is to do a render & replace to a good intermediate codec like Cineform, ProRes, or DNx when you've got something heavy like Warp or Neat Noise Reduction involved with a clip. That will "bake in" the processing to the clip, so that there's nothing about it to re-compute on exit. I do that quite a bit.

The other is to do their "smart previews" process, which works by using the same preview codec as your export will be. So within that, tell it to create previews (again, to the same-as-export codec) and then do check the "use previews" box on export. This may work much better with an intraframe like the three above mentioned codecs than with H.264/long-GOP codecs.

But often, the export is so much faster that you can export to the say Cineform that you used with your previews with "re-import" checked, then use that master file to make your H.264 deliverables, and still save time.

Neil

[ShaunK321]

There's two ways to approach this.

The first is to do a render & replace to a good intermediate codec like Cineform, ProRes, or DNx when you've got something heavy like Warp or Neat Noise Reduction involved with a clip. That will "bake in" the processing to the clip, so that there's nothing about it to re-compute on exit. I do that quite a bit.

Sounds like a better solution that what I've been trying, but of course the other benefit of doing a preview render is that I can play back those now rendered sections smoothly and also continue to edit and not have to re-render the whole timeline. Of course that's IF the rendered previews actually benefited me in reduced export time, which currently they are not.

The other is to do their "smart previews" process, which works by using the same preview codec as your export will be. So within that, tell it to create previews (again, to the same-as-export codec) and then do check the "use previews" box on export. This may work much better with an intraframe like the three above mentioned codecs than with H.264/long-GOP codecs.

But often, the export is so much faster that you can export to the say Cineform that you used with your previews with "re-import" checked, then use that master file to make your H.264 deliverables, and still save time.

So, my issue with this method is that I have several different formats I have to export, so using the same codec for renders as my final export wouldn't apply.

I ended up doing your last suggestion and rendering out the entire video as a CineForm 10-bit file. It's fine, I just wish the previews worked because now if I end up wanting to make any changes, it's kind of a pain to not have to re-render the whole thing again.

Thanks for the suggestions.

[ShaunK321]

So, yeah, huge difference in rendering the file I rendered out with the CineForm 10-bit codec to my blu-ray and dvd formats. Went from 9+ hours each rendering from my timeline with previews, to about 30 minutes each. Just wish there was a more consistent way to make sure Premiere is using the already rendered preview files when you check mark "Use Previews".

[R Neil Haugen]

First ... the first suggestion of mine wasn't rendering previews ... render and replace replaces the original clip in the sequence with the newly created media. Unless you right-click "Restore unrendered" that is the original media as far a PrPro is concerned.

It's just got all changes up to that time cooked into it, so PrPro no longer needs think of them and apply them. Which is why when doing multiple heavy effects like Warp, Lumetri, or video denoising it's so useful. Do one, R&R, then do the other. PrPro only has to compute one on the fly now.

As to using previews ... the previews have to be an intraframe codec like Cineform, ProRes, or DNx and you must export to the same codec. You must have created them after applying all effects to the clip. That way PrPro simply uses the previews without doing any re-encoding.

I don't think long-GOP/interframe codecs like any H.264 can be used for this process.

And what many pros have always done is encode a master, as I said, which is re-imported on encoding by PrPro. This IS the final for the project.

Then all deliverables are created from that master file. So make the previews the same as your master encode will be. Make the master file.

Then in MediaEncoder, you start with that master file, and tell it to make all your deliverables. And it runs away while you go back to PrPro and work on your next job.

Making PrPro the same project, computing the same effects on the same clips three times in a row to get to different deliverables is a waste of resources and time.

Neil

[ShaunK321]

First ... the first suggestion of mine wasn't rendering previews

I understood that. The reason I prefer previews over the render and replace (if the previews also reduced final export time) is that I often have reviews with clients and have to go back and make tweaks to the edit. With render and replace, that means I might have to go back to the original file, make the changes, re-add the effects/transitions, and then do render and replace again. With previews I should be able to just jump in there, make the changes I need and then only have to re-render the small sections that changed. Of course if rendering previews isn't saving me any time with the final output, it only has the benefit of smooth playback on the timeline.

As to using previews ... the previews have to be an intraframe codec like Cineform, ProRes, or DNx and you must export to the same codec. You must have created them after applying all effects to the clip. That way PrPro simply uses the previews without doing any re-encoding.

Okay, I guess that makes sense as to why it didn't go any faster for my blu-ray and dvd exports, but I'm confused as to why it's needing to re-render my clips again when I used the Cineform 10-bit codec for my previews and even exporting to that same codec for my master file caused all of those clips to re-render, taking 9+ hours for the whole timeline. And if rendering a blu-ray export from the Cineform 10-bit master file only takes 30 minutes, why can't Premiere use the Cineform 10-bit preview files it's already rendered on the timeline in the same way?