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Why does render take so much longer than encode?

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Steve Adams
Why does render take so much longer than encode?
on Feb 12, 2017 at 12:47:17 pm
Last Edited By Steve Adams on Feb 12, 2017 at 12:49:38 pm

I'm using PP2017 to to take a 30fps 1920x1080 clip down to 33% speed with Optical Flow, and I notice that if I render the clip, by hitting Return, it proceeds at 3-4 seconds per frame, but if I export the unrendered time line to an output mp4 the encoding runs at about 3 frames per second, 10 times faster. Doesn't the encoding have to do the exact same rendering step to produce the output video?

Thanks


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Alex Udell
Re: Why does render take so much longer than encode?
on Feb 12, 2017 at 3:24:41 pm

Hey Steve....

hmmmm....

what are the render settings for the sequence? (codec specifically) and how does that compare to your source media?

it may be in that codec translation or media scaling from the underlying source media to the timeline render format that the time increase occurs....

back in the days of homogenous codecs for sequence media and render media...this was much more predictable...

since PPro can take just about anything on any timeline....there's a fair amount of comuptation that needs to take place in any timeline render if some front end consideration hasn't taken place to source versus redner settings...


I don't know for sure if I am right....BUT that's my best guess...

Alex Udell
Editing, Motion Graphics, and Visual FX
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Steve Adams
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 12:36:48 am

Thanks. But regardless of the render settings, doesn't encoding to an output file do the exact same render?


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Tero Ahlfors
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 5:33:50 am

[Steve Adams] " But regardless of the render settings, doesn't encoding to an output file do the exact same render?"

Depends on the settings. You probably have different settings for the sequence preview format and the actual export. Take a screenshot of your sequence settings and your export settings.


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Chris Wright
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 1:06:18 am

use previews on in export? you've already rendered the output.


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Duke Sweden
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 2:20:56 am

His question is why is rendering slower than encoding, not how to speed up encoding.


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Alex Udell
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 7:33:28 pm

right...

so what I'm saying is that if encoding settings are close to his source media in nature than his rendering settings...

that can explain why one is differing from the other....and why encoding might be faster...

if his rendering settings were identical to his encoding settings...the speed for each should be the same...

Alex Udell
Editing, Motion Graphics, and Visual FX
Let's Connect on Linkedin
Examples: Retail Automotive Motion Graphics Spots
Example: Customer Facing Explainer Video
Example: Infotainment & Package editorial


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Duke Sweden
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 7:42:51 pm

Actually I was replying to Chris' seemingly misunderstood response, but hey, it's always good to hear from ya, ya bum! ;-)


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Alex Udell
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 8:25:32 pm

heh, heh, heh

Alex Udell
Editing, Motion Graphics, and Visual FX
Let's Connect on Linkedin
Examples: Retail Automotive Motion Graphics Spots
Example: Customer Facing Explainer Video
Example: Infotainment & Package editorial


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Andrew Kimery
Re: Why does render take so much longer than encode?
on Feb 13, 2017 at 8:37:43 pm

As others have said, your preview (render) settings and export setting can make a difference. Also, when you are exporting are you using Adobe Media Encoder? AME uses GPU acceleration by default for exporting where as PPro (whether creating previews/rendering or exporting) only uses the CPU, not the GPU AFAIK.


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Steve Adams
Re: Why does render take so much longer than encode?
on Feb 14, 2017 at 4:44:43 pm

I see all kinds of export settings in the Export Media screen but I don't see much about render settings, other than optimize for performance or memory, so I don't know how to compare the two settings.

Also, I'm not using AME.

Thanks


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Andrew Kimery
Re: Why does render take so much longer than encode?
on Feb 15, 2017 at 2:03:36 pm

[Steve Adams] "I see all kinds of export settings in the Export Media screen but I don't see much about render settings, other than optimize for performance or memory, so I don't know how to compare the two settings."

In the Sequence Settings window there are is a "preview" section near the bottom and that's where the settings are for making previews/renders. The number of options available in the preview setting is in part dependent on your sequence settings. For example, if your sequence is setup for Avid DNX then you will only be able to create previews/renders in the Avid DNX codec. By changing your sequence settings you'll be able to change which codecs are available to use for previews/renders.


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Steve Adams
Re: Why does render take so much longer than encode?
on Feb 16, 2017 at 4:02:05 pm

Thank you!


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Steve Adams
Re: Why does render take so much longer than encode?
on Feb 17, 2017 at 4:03:09 pm

One more data point. I believe the reason the render I did by hitting Return took so much longer than the render that occurred during export is that the source is 1920x1080 while I was exporting to 1280x720. So the first render had to manage 2 million pixel frames while the export render worked with 1 million pixel frames. And I have a feeling that render time may be an exponential function of frame size, so doubling the frame size might quadruple the render time.

Anyway, thanks to everyone for their input.

Steve


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Tero Ahlfors
Re: Why does render take so much longer than encode?
on Feb 17, 2017 at 6:57:11 pm

You still haven't provided us the exact sequence and export settings so we don't know what you're doing.


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