Faster preview trick. Is this a good idea?

johnmeyer wrote on 4/23/2004, 8:45 PM
I saw in another thread a multiple cat demo by chaboud (Cat Demo).

If you download the whole project, you will find that he set the project properties to 360x240, i.e., one quarter resolution, even though the media is 720x480. I tried to figure out why he would do this, and then it hit me:

If you do this, your preview speeds up tremendously.

It is actually a pretty neat trick if you think about it: Do all your editing with the project properties set to low resolution, and then, just before final render, bump it back up again.

I looked for this in old messages, but didn't find anything. Is this a well-known trick for trading off spatial vs. temporal that all you pros out there have always known about? I sure didn't know about it.

Using this trick I was able to get 29.97 frame rates in the preview window (albeit at lower resolution) on effects that were still jerky even at draft resolution. It also worked when sending the video out to the NTSC monitor.

Comments

vitamin_D wrote on 4/23/2004, 9:00 PM
- jim
ibliss wrote on 4/23/2004, 9:01 PM
I think you may potentially run into some problems going down this route. It's fine for general workflow, as you say, but when you switch back to 'normal' resolution some vid effects may actually appear differently. Not vastly so, and if you are prepared for this, then no problem. Something to consider though.

Also, generate media by default is created at the project resolution, so when you scale back up to DV size, titles and the like will not look as sharp. You can get round this by changing the gen media to the big frame size later, a bit dull. I expect someone could perhaps create a script to resize all generated media..... who could that be i wonder :)
Cheesehole wrote on 4/23/2004, 9:13 PM
Either I need to see exactly what I'm going to get pixel for pixel... or I want to see the animation as smooth as possible. So I use Best or Draft and ignore the rest.

In Best mode the preview frame rate can actually go down using a lower frame size, and I wouldn't be seeing exactly what I'm going to get...

Just depends on your priorities. If it works for you it's a good idea! :D
taliesin wrote on 4/24/2004, 6:13 AM
I just tried that trick but it does not seem to work. There is no improvement for the preview then on my systems. Not even on a simply dissolve. Furthermore it even slows down the preview playback rate a little bit for clips without any fx.

Is there anything else to watchout except the project properties frame size?

Marco
johnmeyer wrote on 4/24/2004, 12:47 PM
I need to see exactly what I'm going to get pixel for pixel... or I want to see the animation as smooth as possible. So I use Best or Draft and ignore the rest.

I agree completely: If you don't want to wait for a pre-render you typically either want to get either the best spatial, or the best temporal quality. What this "trick" does is give you another temporal speed level that is up to 4x faster than "Draft." The video gets pretty coarse, but the frame rate can go up to 29.97 (or 25) even on pretty complex effects.

I just tried that trick but it does not seem to work.

Make sure you use some fX that really slow things down, so that you only get a few fps, even in draft mode. Than, click on the project settings icon on the preview window, and change width from 720 to 360 and height from 480 to 240. You should see 4x the frame rate. The difference is not subtle. I guess there are some circumstances where the downsampling time can outweigh the benefits, but if you are doing lots of compositing and effects and cannot get enough frame rate to really tell what is going on, this "trick" might really help. Network rendering might have been a better solution, but apparently -- if I have correctly read what other people have said -- it doesn't get used for pre-rendering.
taliesin wrote on 4/24/2004, 1:01 PM
Mmh, I applied both Gaussian Blur and FilmEffects (Preset: Very Old Film). I first playbacked using the PAL DV settings and preview set to "Good (Auto)". This results in playbacking a frame rate of 3.5 fps on my system.
Then I switched the project settings to a frame size of 360x288 which is half of PAL DV settings.
Now the playback rate is at 2.1 fps.

Whatever I do using a smaller frame size than PAL DV for my PAL DV files does slow my preview down.

Marco