Why does Premiere re-Render on Export?

[Douglas Turner]

Hi all,

I've used Premiere for years, but not really asked this question before!

When you've already rendered your timeline... and you're exporting the movie in the same format as the project - why does Premiere painstakingly re-render the whole project?

OK - I am using Cineform HD codec, Boris Continuum Deinterlace, Magic Bullet Colorista and Looks... but that's all rendered already.

Am I missing something? Would've thought the already-rendered files would be used to build the output.

Anyway, I'm sure there's a valid reason!

Posted here, as I'm sure it's not just a Cineform question.

Cheers, Doug.

PS- it's taking 7 mins to export 15secs of the timeline - when remove the effects (Deint, Color, Looks), it takes 35 secs to export the same 15secs!

[Douglas Turner]

No thoughts from anyone? Or was it just a stupid question?!

[Harm Millaard]

I believe that Premiere renders on export and does not use the preview render files, that were created by using Enter.

[Douglas Turner]

Hi Harm,

Yep, that seems to be evident - the question is... why is this necessary?!

In which case it's quicker for me not to enable any effects while editing and just turn them on when it's time to Export.

I was just wondering whether I was doing something wrong - if previously rendered Preview files weren't being found by Premiere etc...

Cheers, Doug.

[Harm Millaard]

Doug,

These are WAG's, but maybe:

1. A lot of people never render the time line while editing and thus not creating preview files, so for those you need to create new render files anyway.
2. The programmers may have had limited fidelity in the preview files.
3. The preview render files may not be full resolution and FPS, just to save space and increase responsiveness.
4. Maybe this will be improved in CS3.

[Steven Gotz]

The real answer, no guessing involved, is that if you export to DV AVI from a DV AVI sequence, the program uses the preview files.

If you are exporting to something else, anything else, you don't want the original content to be encoded twice - once to DV AVI and once to whatever you are encoding to.

For example, encoding to MPEG2-DVD, there are slightly different rules involved than in DV AVI. Things that DV would not like are generally OK in MPEG2. Like fine lines.

So, while it takes a long time, it is better for you to have the program encode from the original media, and not the preview files.

[Harm Millaard]

Steven,

The OP is talking about HDV. Why else would he mention Cineform HD? Does that fall in the same category of real certainties?

[Steven Gotz]

Same basic idea. He would be previewing in the Cineform codec, but I doubt Premiere Pro knows to use the preview files since as I said, the only time it does is when it exports DV AVI from a DV AVI project.

I exported a Cineform AVI using a Cineform AVI on the sequence. It happens to be 1;14;18 in duration.

Exporting that file took 1:56, and if I applied an effect (native not Cineform), it took 2:22, and if I rendered it first, it took 2:22.

Douglas never said what he was exporting to. If it is Cineform HD AVI, I think his numbers are off a bit. If something else, then it is to be expected.

Once again, I stand by my statement "if you export to DV AVI from a DV AVI sequence, the program uses the preview files".

[Graham Hickling]

Surely the sensible "rule" for the Premiere to implement would be that if you are rendering out to the same format as your project settings, use any previews that are available!

I mean, obviously if you are rendering DV to mpeg, the previews are of no value. But if it's AVI project to AVI export, same codec and compression, why chuck away the previews???

[Steven Gotz]

You are right, of course, but I doubt that Premiere Pro knows enough about the Cineform project to know it should use the previews. We need to ask David Newman if there is anything Cineform can do about it. Or, am I wrong? Do we need to harass Adobe?

I'll point out this thread to David and we'll see what happens.

[Douglas Turner]

Hi Folks,

Yes, to clarify it's a CFHD project and I'm going out to CFHD avi.

It basically re-renders the timeline I'm exporting - so taking roughly the same amount of time to export as it would to re-render.

Pretty sure the Render Preview files are full-res, but don't know if they're in CFHD avi format (I'll re-check this when I'm at home).

If, Steve, you're sure it's not a Premiere Pro issue - and most likely a Cineform issue I'll relocate the thread over there.

...and I'll test with PPRO CS3! - which I have got working with CFHD projects, but the speed increases reported by other users weren't so impressive for me.

PS- My numbers for the time taken to render/export were correct, even though I have 4GB RAM, Dual Core AMD etc - Boris Deinterlace (using Motion masking), Magic Bullet Colorista and Magic Bullet Looks takes it's toll on render times!!

[David Newman]

As there are several internal stuctures and formats to CineForm files, we haven't yet done a compressed data copy from the input stream. It is on the list, but it is tricker to do than DV which has only two variations (PAL and NTSC -- rarely mixed.) However, I believe Premiere Pro use will not use preview (transition renders) in generating an export movie -- there is a good reason for this, but it escapes me at the moment.