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Pre-Render Format & RAM Preview Issue

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Tom Hawcroft
Pre-Render Format & RAM Preview Issue
on Aug 15, 2014 at 7:59:29 am

Hi there,

Couple of queries I think may be linked but not sure...

I pre-rendered a heavy comp as an AVI and imported it back to replace the original footage. But now I can only RAM preview about 15 seconds, whereas my footage is about twice that length. The AVI is pretty big at nearly 6gb, so I put it on an external drive. I thought pre-rendering was a way of making things faster, but I can't see how 6gb is any easier for the system to deal with.

Should elements like this be kept on the local disk, or is there a better lossless format I could choose as a pre-render?

Many thanks!


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Walter Soyka
Re: Pre-Render Format & RAM Preview Issue
on Aug 15, 2014 at 11:10:52 am

Even if you used a compressed format, Ae will still decode it and store it uncompressed in RAM for preview.

Without the pre-render, Ae would still require all that amount of RAM (uncompressed RGBA at the bit depth of your project), plus whatever RAM it needed to calculate all the layers inside the comp, plus CPU time to compute effects and blending.

There's nothing wrong with putting the RAM preview on an external drive, but if accessing that disk is very slow, it will drag down performance.

What are your system specs?

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Tom Hawcroft
Re: Pre-Render Format & RAM Preview Issue
on Aug 15, 2014 at 11:46:42 am

Hi Walter,

I suspect my system specs are embarrassingly weak, 5 year old Dell laptop with 4gb RAM... but I haven't had any problems previously with the preview stopping short, so I will suspect it's either the file being stored externally, or that other applications were draining the memory.

It's very useful to know that the pre-render format doesn't really matter in terms of the preview, but would you say that full blown AVI (for a PC) is the best lossless format for this? I saw one tutorial recommending an image sequence.

Many thanks for the response, all knowledge and advice gratefully received...

Tom


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Walter Soyka
Re: Pre-Render Format & RAM Preview Issue
on Aug 15, 2014 at 12:03:18 pm

[Tom Hawcroft] "I suspect my system specs are embarrassingly weak, 5 year old Dell laptop with 4gb RAM... but I haven't had any problems previously with the preview stopping short, so I will suspect it's either the file being stored externally, or that other applications were draining the memory."

I'll bet that you were using a lower resolution for your earlier previews; this requires less RAM than the full-res render.

If you share your comp settings (comp size and frame rate) and project bit depth, I can explain the math involved in the memory consumption a bit better.


[Tom Hawcroft] "It's very useful to know that the pre-render format doesn't really matter in terms of the preview, but would you say that full blown AVI (for a PC) is the best lossless format for this? I saw one tutorial recommending an image sequence."

I like image sequences for a few reasons: you can easily re-start interrupted renders, you can easily re-render only a small portion of the total length, and you can process them externally with all kinds of other tools.

However, image sequences can also run a bit more slowly on mechanical hard drives (accessing many files versus accessing a single one).

The container should have no bearing on RAM consumption, though.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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