Rendering time

PaulT1 wrote on 1/5/2003, 9:34 AM

I have edited 2 one hour parts of a movie, both with about the same amount of transitions , titles, audio and videoFX. When I rendered the first part it took little more than 1 hour, the second part took 8 1/2 hours even though the box "fast video resizing" was checked. The rendered movies are both fine and I cannot detect any differences on the final result.
What may be the reason for the big time difference in rendering?

Comments

ralphied wrote on 1/6/2003, 10:18 AM

Were you rendering both files to DV format or to some other format, say MPEG-1 or -2? It almost sounds like the first one rendered to DV format and the second one to MPEG-2.

Depending on the number of titles and transitions, a 1:1 render time seems reasonable when rendering to native DV format. However, rendering times on the order of 4:1 are more the normal when rendering to MPEG-2.

If the second part was, in fact, render to DV format, you have some serious problems because it should never take a 8:1 ratio.

I have also run into occassions when DV rendering times did seem to take long, and I knew there was a problem because the hard disk activity light was not on constantly. Except for transitions and titles, the hard disk activity light should be on almost constantly because the software is smart enough to realize re-rendering of these portions is not needed and so the process is just about a direct disk transfer. The problem turned out to be a process running unknowingly in the background that was hogging up the CPU.

The next time you render it and it seems to be taking longer than usual, open up Task Manager and see if there are any other processes running that are using CPU time. If there is a process, shut it down ("end task") and you should see the rendering speed back up.

I hope this helps.

Grazie wrote on 1/6/2003, 10:40 AM

Does rendering to a avi first cut down the Total render time?

Chienworks wrote on 1/6/2003, 11:41 AM

Generally rendering to AVI is faster than rendering to most other formats because there will be less compression going on (although, as i sit here and type, i'm doing a few renders to AVI using Cinepak and it's crawling, but then, Cinepak is rather extreme compression). However, Rendering to AVI first, and rendering that output to a more compressed format will take longer than rendering directly to that compressed format.

There is one good use for rendering to an AVI first though. Quite often, i'll render projects to a wide variety of formats and bitrates. If i render to a DV .avi file first, then all my transitions, fades, composites, etc. only have to be rendered once. All the compressed renders to .wmv, .rm, .mpg, etc. files from the rendered AVI file will proceed much quicker than if i rendered each output file from the original project. Quality loss is negligible since most of my source was DV anyway.

Grazie wrote on 1/6/2003, 12:33 PM

Clear and intrstructive as ever! Thanks Chienworks. We have been having some really nice clear crisp days in London. Just been out filming our local park which has some "cute" parakeets etc. Lots of yellows and blue sky - oooohhh I feel a Chienworks upload soon. Just looove this Canon XM2.

Grazie

PaulT1 wrote on 1/6/2003, 4:28 PM

Thank you for your help, unfortunatly the problen is still there.
In reply to your suggestions, both movies (lets call them movie-1 and movie-2)
were rendered to the Video for Windows (*.avi) format and during both renderings
no other programs were running.

I have 2 hard disks with a total of 120 GB partitioned into 5 parts of which I
use 1 partition of 60 GB exclusively for video work. In order to make space on
this video partition I have moved the previously rendered movie-1 and movie-2
onto another partition and made the following tests.

I have re-rendered 20 minutes of both movies since I have the associated project
files and media pools still on the disk and got the following results:

The estimated size for movie-1 was indicated as 13.03GB
The estimated size for movie-2 was indicated as 13.16GB
The approximate time left for movie-1 was 00:27:06 and completion was 42%
The approximate time left for movie-2 was 07:15:00 and completion was 4%
And the size of the partially rendered movies after the 20 minutes was approx.
5.5GB resp. 520MB

This test was done exactly with the same setup, one right after the other, and as
you correctly stated ecxept during transitions and video overlay titles the hard
disk activity light is on constantly for movie-1 but not for movie-2.
There must be a difference in the project file between the two and I wish I knew
what it was. I can live with it and do the rendering over night (unless I have a
power failure) but I would still like to know the reason. I have previously
rendered about four or five other 1 hour movies and never encountered this
problem.

BillyBoy wrote on 1/6/2003, 4:47 PM

Did you apply any FX filters? Some are very slow. Like Median.

IanG wrote on 1/6/2003, 5:34 PM

Purely in the interests of science, could you try booting the system, rendering Movie-2 first and then Movie-1? I have absolutely no idea what's going on, but this would give another indication of where to start looking.

Ian G.

PaulT1 wrote on 1/6/2003, 8:15 PM

On my last test I rendered the 20 min. of movie-2 first and then the 20 min. of movie 1 (I guess I had also a suspicion that this may have anything to do with it)
You have seen the result.

Now I made another test:
I rendered only a loop region of 2 minutes (00:02:00,07)for movie-2 and (00:02:00,08)for movie-1 both containing no titles no transitions and no videoFX with movie-2 first, followed by movie-1. The rendering times were 15:26 for movie-2 and 1:16 for movie-1

ralphied wrote on 1/6/2003, 8:43 PM

Is it possible that you might have done some trimming on the timeline by clicking on the end of an event (either start or finish) and dragging the cursor WITH THE 'CTRL' KEY inadvertently PRESSED? If you happended to do this, you changed the playback rate. This would result in a complete re-rendering of the file similar to as if you would have had a transition applied to the entire event.

I would try recreating (retrimming) the original second movie file.

JohnnyRoy wrote on 1/7/2003, 4:15 AM

Yea, my guess would be the playback rate got changed by accident. Go into clip properties for all the clips and make sure the playback rate is set to 1.000 for each one of them.

~jr

PaulT1 wrote on 1/7/2003, 10:12 AM

Thanks for the hint. You just told me how to slow down or speed up an event, something I have not found in the manual.

I checked all events for the playback rate, it is 1.000 on all of them. Even if this would have been the case, it could have affected only the particular event and would not account for this large increase in rendering time.
During rendering of movie-2 it appears as if all events had been modified since during the entire rendering process the harddisk activity light turns on and off.

Well, I guess I will just have to live with it on this movie and hope it does not happen again. Perhaps I may later on find out what it was.

Former user wrote on 1/7/2003, 10:24 AM

Is there a chance, and this is just a guess, that one is being rendered at a different quality than the other?

Dave T2