Two quick video questions.....

Glen_Elliott wrote on 8/26/2003, 9:28 PM
Two quick questions:
1. When I'm playing back footage on the timeline and click an area on the timeline ahead causing the cursor to jump to that position I notice my frame-rate takes a quick dive and comes back up....this is normal right?

2. This may be a bit hard to explain but- if I resize my preview window to full size whether it be full-quality or preview- I encounter a weird wavy-jitter kind of phenomenon during areas of large constant movment- like pans. Kinda hard to explain other than the image almost looks like it's shearing. Is this normal? When the preview window is about half size (half resolution) it doesn't appear to be as noticeable. Mainly when the preview window is full size (720x480).

Comments

theigloo wrote on 8/26/2003, 9:50 PM

1. Yes - normal. You're HD needs a little time to figure out where you told it to go and start reading. There will be a short lag.

2. Sounds like you have a slow computer or a slow HD. What are your system stats?
DataMeister wrote on 8/26/2003, 9:50 PM
I think what you are seeing probably fairly normal. Both of those symptoms sound like something regulated by the CPU and hard drive speeds.

It should be normal (as far as the laws of physic are concerned) from the frame-rate to drop a little as the hard drive heads move from one location to another to pick up the data for that location of the video. If everything goes back up to the same frame-rate then I would say it should be working fine.

The preview window shearing is probably because the CPU isn't able to decode the video fast enough. Is this video in a format capable of using a variable bit rate? Something like MPEG2, or WMV, etc.

JBJones
DataMeister wrote on 8/26/2003, 10:01 PM
Man! igloo,

You beat my post by 8 seconds.

JBJones
theigloo wrote on 8/26/2003, 10:03 PM

Well we both said the same thing - so we must be on to something :).
Glen_Elliott wrote on 8/26/2003, 10:15 PM
Athlon 2200+, Asus A7V33 mb, 512mgs DDR Ram, Gforce 4 Ti 4600, OS drive Maxtor ATA133 40 gig, Dedicated video drive Maxtor 80gig.
It's definitly no slouch and my new PC is even better- P4 3.0ghz, Asus P4C800-E delux mb, 1024mgs dual channel Corsair XMS 3200 ram, dedicated 240gig SATA Raid-0 vodep drive....though I haven't had the time to install Vegas and test it on that machine as well.
One note that might be of interest is that I'm now utilizing Nview (dual LCD monitors) so my desktop is now running at 2560x1280. Don't know if that might have anything to do with it?

Regarding the video "shearing" Jbjones mentioned it might be my CPU having trouble decoding the video, and asked what format it was in. ----This is happening from within Premiere and the format is the default AVI format that Vegas captures.
DataMeister wrote on 8/26/2003, 10:35 PM
Oh.

My theory was that perhaps the CPU was having trouble decoding the extra information during the higher data rate of a fast scene. However DV is a constant data rate so that theory goes down the drain.

Maybe it is based some how on the video adapter not being able to refresh fast enough with that much screen realestate.

Does the effect still occur when you reduce the resolution to a single screen?

JBJones
GmElliott wrote on 8/27/2003, 2:19 PM
Do you think it might have anything to do with the fact I'm using dual LCDs and not CRTs. I know the main concern for LCDs is ghosting and this definitly doesn't look like ghosting.
DataMeister wrote on 8/27/2003, 2:37 PM
I would think something more along the lines of the graphic card memory not being fast enough to seamlessly redraw that many pixels that fast. But I don't know for sure. It's just speculation.

JBJones
Glen_Elliott wrote on 8/27/2003, 3:32 PM
n/t
BillyBoy wrote on 8/27/2003, 3:53 PM
If Vegas is feeding out via firewire your video card is totally out of the loop. You could have 1 GB of ultra fast DDR RAM on the video card... wouldn't help a bit. If you're not happy with the playback speed of preview, and you can't live with dropping the quality down (that will speed up play back) then the only thing that really improves playback is a FASTER CPU.

I think I must have said that 50 times at least recently. :-)
Glen_Elliott wrote on 8/27/2003, 9:21 PM
It was the preview window from within Vegas, not via IEEE to external monitor. It doesn't seem to be a problemw when the preview window is small- but when I resize it at "full size" thats when I see the video sorta shearing during pans.
DGrob wrote on 8/28/2003, 2:45 PM
Just curious, do you have any video output FX applied via the preview window icon? DGrob
GmElliott wrote on 9/4/2003, 9:09 AM
I think it might actually be my display. I just recently switched to LCD display. Despite the fact it boasts a 16ms pixel response maybe I"m seeing some sort of pixel delay artifacting?! Anyone have any insight into this?
PDB wrote on 9/4/2003, 10:51 AM
As per the "shearing" sound like what you are seeing is the effect of interlaced video on a progressive monitor...If so, it's perfectly normal I believe...you probably can't see it on a small preview window cause....well because it's small...
riredale wrote on 9/4/2003, 11:43 AM
I agree. Each field in an interlaced frame is from a slightly different point in time, so if you combine two fields (which is what Vegas does when you ask for a full 480x720 presentation) there will be a strange sort of "comb" effect on edges. You don't see it on a small window because presumably Vegas is smart enough to just use one field for the presentation.

On an interlaced TV, everything will look fine.