Found workaround to lagging PinP preview

nolonemo wrote on 4/25/2007, 8:31 AM
This is probably obvious to the old timers, but I just figured it out and wanted to share with the less grizzled users.

I have 4 tracks of video sync'd and sized to display 4-up in the preview window using track motion, so I can view all cameras simultaneously on playback and mark cuts. Unfortunately this puts enough load on my system that the preview framerate in draft full mode is around 8 fps, too jumpy to be able to judge video quality (I'm editing parent-shot video of a concert, so the quality of pans and zooms is variable, not to mention intermittent spastic framing adjustments). I haven't been able to get the frame rate higher, even trying a bare install of XP and Vegas to minimize system overhead.

Anyway, I realized that I could render the 4 tracks sized for the PinP to a single .avi, place that on a new video track, mute my 4 original tracks, and play the "preview track" back to mark my cuts. Works like a charm, I get full 29.9 framerate in full preview mode, probably could go to higher quality, too.

Once I've made and adjusted my cut marks, I'll delete the preview track, cut and put the final edit of the 4 tracks together.

The only downside is the render time to get the preview track, but that's a "let it run overnight" deal, so no biggie there.

I'm a happy camper again!

Comments

johnmeyer wrote on 4/25/2007, 1:42 PM
Well, you may be able to achieve your goal without the rendering. Here is how to get full frame rate -- even on my lousy old computer -- without pre-rendering the whole darn thing.

I just duplicated your situation. I put four tracks into a new Vegas project. I put four different DV AVI files (NTSC) onto the four tracks. I then used Track Motion (don't use the PIP fX -- it is slower) to re-size each to 360x240 and positioned them into the four corners of the screen, thus giving me the 4-up that I think you are describing. I cancelled the building of audio peaks so that process didn't interfere with my tests.

I have a very old computer (almost four years old) with a single CPU, single core, single-thread (yes, not even hyperthreading) P4. Using the "Preview (Full)" quality on the computer display (no external display) and with no videoscopes displayed (they can reduce playback rate), I got 10.3 fps, according to the fps meter on the preview display. It bounced around a little, but that was roughly the average.

I then did two different things.

First, I took one of the AVI files and copied it from my internal IDE drive (all four of these files were on the same drive in the same folder) to another drive. Once it was copied, I removed the original instance of this file from track 3, and also removed it from the project list, so Vegas would definitely not be looking for it at all. I then instead dragged the copy of this file from the folder on the second drive. I then previewed again.

This time I got 16.0 fps. That's a 60% increase achieved simply by putting one of the four files onto a separate drive.

So, the first piece of advice is that if you have more than one drive, for heaven sake, put each camera's video on a different drive. If you have four drives, put each camera's video on a different drive. Make sure it is physically a different drive, and not just a different partition (drive letter) on the same physical drive. Also, if possible, use a drive that is not in a master/slave relationship with the drive that contains your other video (although the test I describe above was actually done by copying to another drive that IS a slave and therefore on the same IDE channel). The problem with reading four files simultaneously from the same disk drive is that the Window O/S and the disk drivers are not just designed to stream four simultaneous streams (although the old BeOS WAS designed for this, but that is a story for another time).

Now, if you want even more performance, and are willing to trade spatial resolution for fps, then you can go to the project properties (located on the preview window) and change the project properties from 720x480 (if you are NTSC) to 360x240. I learned this trick four years ago from one of the Sony engineers who posted a solution to some other problem. If you have Vegas 7, you can stretch the preview window back up to the same size (right-click and then select "scale video to fit preview window"). I just did that, and I went from 16.0 to full frame rate.

Of course, if you do this, you MUST remember to switch back to 720x480 before you render!

Hope that helps!!

Zulqar-Cheema wrote on 4/25/2007, 2:53 PM
Just so you don't forget , put a bit of text at the front of the video to remind you to change back.
jaydeeee wrote on 4/25/2007, 4:42 PM
This J.meyer post might even be grounds for a sticky. Good suggestions!
nolonemo wrote on 4/25/2007, 4:51 PM
Dang, and I thought I had been clever! Thanks, John, I hadn't thought about the bottleneck from simulataneous streaming off of one drive. Unfortunately, I "only" have Vegas 6, and I really need the larger preview window. But since I have two HDs in the laptop, I'll try putting two avis on one and two on the other, if I can get the framerate up to around 18-20, I think I would be OK.
johnmeyer wrote on 4/25/2007, 5:16 PM
First, thanks for the kind words. I always try to help, and I spent a little time on this one, so I am really happy that it may actually be useful.

I think that, with your better computer (compared to mine) that if you can at least split the four cameras across two drives (and three or four would of course be better), I'll be you can get full framerate in Preview mode (Draft mode is too horrible to contemplate -- you definitely want to ditch that, if you can). As for getting a larger display with V6, my recommended solution to that is to use an external monitor. Near as I can tell, the clever engineering behind the Firewire preview doesn't seem to diminish the framerate by much at all. However, if you do use this, you'll probably want to NOT use an external Firewire drive for one of your video streams. Use USB, SATA, or internal IDE instead. Also, the MAIN problem here is telling one set of heads to go four places at the same time. Therefore, even with the bottlenecks of having all the video streaming over the same IDE or USB channel, you'll still be WAY ahead of the game compared to getting it from one drive (which by definition is streaming over one channel).

I'd bet good money that, before fX and any other things that will slow it back down, that you'll get full frame rate, or very close to it, if you can get the video on four drives.

farss wrote on 4/25/2007, 5:33 PM
On the audio side of this is one advantage of file formats like BWF, the multiple audio tracks are interleaved.
Which reminds me of another trap. ALWAYS make certain your audio project properties match your media's properties. Vegas's default is 44.1K which means all DV audio is being resampled.
And another. Check your audio tracks media properites. Due to a snafu in VidCap it's very easy to end up with 16/32K audio, Again this imposses a CPU overhead with resampling.
If you've extracted audio from a CD you can also give the CPU a helping hand by prerendering the track to 16/48K, again to avoid it being resampled everytime you playback the track.
Also changing Resample from Best to Good will also reduce CPU overhead IF resampling is being done. If you are resampling audio always switch to Best for the final render.

Bob.
johnmeyer wrote on 4/25/2007, 5:55 PM
Which reminds me of another trap. ALWAYS make certain your audio project properties match your media's properties.

Bob, thanks for reminding me. I forgot to make that change when I upgraded to V7 and for the past six months have been running with 44.1. I have now set the default to 48k.

I also deleted those three unnecessary plugins which, by default, are loaded onto each audio track (although Sony claims that their presence on each track doesn't suck cycles).