sudden slow down when rendering a video (solved)

Hussayn wrote on 10/18/2008, 4:10 AM
Hi;

i noticed a weird effect with rendering speed (i use "vegas pro 8.0b (build 217)" )

I was preparing for a 90 seconds teaser video.
Yesterday i rendered several times and could achieve rendering times
of about 120 seconds for a .mp4 rendering and nearly the same for a best
quality .wmv rendering (2 sound tracks, 2 video tracks)

Now today, i changed some small parts like the trailing info panel and i added
one 3 seconds scene right in the middle of the video. So apparently no big modifications.

But now my rendering time jumps up by a factor of 3 to about 350 seconds. The
computer configuration did not change, nor do i have massive background tasks
running. I am not doing any fancy things at all, especially nothing different
compared to yesterday.

I only temporarily changed the project settings to check out something, but i
returned the settings back to original before my final rendering. So what could
cause such a slow down and how could a debug the cause ?

Any hints ?

Comments

farss wrote on 10/18/2008, 4:44 AM
What is your source footage, is it HDV by any chance?
If so it's possible the 3 second scene you added has an error in the mpeg-2 stream that takes Vegas a long time to resolve. If that guess is correct you could try converting that 3 second clip to uncompressed HD. As it's only 3 seconds long the file size will not be too huge. Alternatively you could also use the 8 bit Sony YUV codec.
Of course I'm making a lot of assumptions here.

Bob.
Hussayn wrote on 10/18/2008, 6:23 AM
Hi, Bob;

Thank you for your hint. After i read your entry, i took another round on this problem.
No, i do not have HDV or mpeg-2 based footage. It is all from fraps and crazyTalk
(i am making machinima moovies). So i looked again at the property setting and
experimented a bit. And it looks like i eventually found the problem:

there is one project property named "pixel format", which i probably have touched
unintentionally. It was set to "32 bit floating point". When i set it to "8-bit" the
rendering speed instantly jumped back near to what i had before.

So i looked in more detail on rendering quality. So far my project does not seem to
suffer from this change regarding that. So i guess, my problem is solved, as the
documentation clearly states "32 bit format consumes significantly more cpu
resources" which is exactly what i see.

Thank you anyways for your response. It was still helpfull to push me toward the
solution.
farss wrote on 10/18/2008, 7:06 AM
I should thank you, being the curious type I looked up Fraps and CrazyTalk. Looks like fun.

Bob.