firewire questions

FIRST General Forum
1

im trying to make a video for the robotics and im trying to do a motion screen capture of the computer screen. I’ve tried programs like camtasia which will let you capture the desktop but a lot of frames get dropped so it looks choppy. I was thinking of how a dv cam connects to the computer and I thought, what if i connected 2 computers via firewire and had one output its screen so that i can see it on the other computer and record it with a capture program like what adobe premiere has. I don’t even know if this is possible and that’s why I’m asking if anyone has any experience on this subject.

p.s. The computer im on now has the radeon 9700 pro which has a svideo out. and my other computer has the radeon 8500 pro which has the svideo in. So i tried that way, from the svideo to this to the input of the other computer, but the screen came out blurry. This is the closest i’ve gotten to a smooth video but its blurred so it’s useless.

any ideas?

2

We use Sony DCR-VX2000 cameras and computers with Premiere and firewire. We plug the firewire into the camera and into the computer. Then, have you’re project open in Premiere. Then with the camera on the VCR (? not filming) setting, press both the record and blank square buttons at the same time. These buttons can be located on the top of the camera in the flat button tray. Then, press the play button in the monitor window of Premiere. The camera should now be recording what you are playing on the computer. Here is a pic of the cameras we use:
http://www.fotovideoshop.nl/media/sony_dcr_trv2000.jpg

3

Ryan,
I am not sure what you are trying to do. If you have some computer animation on your computer that you want to port out as video, you are going to have to expect problems but there are a variety of converters that are made to do that. If you are trying to edit from a video file, then you need a file converter to take the original file to whatever format you need for your editing. If you are trying to generate a firewire output stream from an internal file, there is software for that too. (It usually comes with the DV Cam so that you can transfer, edit and return to the camera.) Most editing software or video playback software allows you to choose to port out to a video monitor if the hardware is correctly installed.
Remember that the DV Cam is an embedded digital source (stream) as it is recorded. The import software that makes use of the firewire connection, talks to the camera through the firewire and imports and converts the digital video as it is played back on the camera. (Essentially, yet another file conversion.) To complicate matters more, standard definition TV signals, whether digital or analog are sometimes known as 640i or roughly 640x480 interlace, 30 frames/sec. So any conversion from the computer screen to video must conform to this and the result is lowering of resolution(somewhat out of focus), video stutter, etc. High priced software can correct all of the problems but the secret word(s) are “high priced”. I know that our schools use a variety of products running on Apple Computers, which allow file conversions and editing in one package with firewire import and output. I think it is called Imovie.

4

You could do what you want to do with any DV camera… personally, my family has a family-geared Sony camcorder:


It has the option to record to Digital8 tape from sVideo or rca. I’m sure Sony’s not the only one who makes DV cameras that can do this - probably almost any DV camera can do this. If I was doing what you’re trying to do, I’d just setup the camera to record from the sVideo input onto D8 tape then just hit the rewind button and record the input like normal (Premeire, Sony generic software, Windows MovieMaker - capturing through Firewire is common nowadays).

5

My recomendation would be to do a video out to a VCR or the camcorder. Then import that into Adobe Premiere.

BTW Guys, he wants good video screen capture.

6

*Originally posted by JosephM *
**BTW Guys, he wants good video screen capture. **

‘good’ is relative.

I captured some of my robotics videos from a competition from the above-camera. I’d say I got a ‘good’ capture from a $400 camcorder as opposed to a $3000 camera like the kind sanddrag uses. If you have a $3000 camera, go for it. For the rest of us, well…

Also something that you want to consider is resolutions and resizing like Al began talking about. By ‘video,’ I suppose Ryan is talking about he wants to combine video footage with computer captures (Inventor, MAX, etc.) to make a little promo tape. If you’re doing any serious work with those programs, you’re using atleast a resolution of 1024x768. With my little camcorder, the highest capture size I could get is 720x480. So, there’s going to be a significant amount of screen reduction anyways. Al talked about how standard tv signals (i.e. svideo) is 640x480. So basically, you want to take a 1024x768 resolution signal, resize it to 640x480 (for svideo), send it to the camera, and let the camera do whatever the camera does. This in itself is a considerably lossy process - not to mention the loss that you’ll expierience in recapturing. I’m sure the more money you push into your equipment will get better results - i.e. a $3000 pro camera as opposed to a $400 family-geared camcorder. My advice is unless you’re really into digital video editing, accept the lossiness and move on - that money can be spent on better things.

Actually, now that I think about it, this kind of process is VERY lossy. You’re probably better off looking for some kind of SOFTWARE that captures the screen input.

Also something that you need to consider is size. Video can get REALLY REALLY REALLY big. I mentioned I captured some robotics videos at 720x480. Even AFTER DivXing them (DivX is a compression scheme that has been called the MP3 of video), a 4:22 long video file at 720x480 is 140megs. Although I did use a video/audio bitrate that was probably a bit too high (hmm… actually, now that I think about it, the bitrate was way high), it does give you an idea of the size that you’ll need for ‘good’ videos. You’ll also need a few gigs of harddrive space to store the raw footage BEFORE compression.

Anyways, the point of all this is that ‘good’ comes at a price. If you’re a videophile, then sure - empty out the wallet. For the rest of us, well… yeah.

In conclusion: look for a software program for capturing your screen. There’s gotta be something like that out there.

7

i dont really care about the size of the file. (i have a 320gb hard drive along with 2gb of ram). You were talking about a software capture. I tried one called camtasia which is by techsmith. It was dropping frames like crazy. That’s why I’m asking if there is a more effecient way of doing it. I thought firewire would of been able to output the computers screen so i could record that using my computer/other computer, but i guess i cant

8

About the size, I was implying more if you wanted to make it a promotional type of dealie, the easiest would be for it to be under 700 megs so it could fit nicely onto a cd-rom. If this isn’t your goal, well go nuts with the memory (sounds like a nice system you’ve got there). It all depends on what your plans are.

And about Firewire, we didn’t say you can’t. We were just talking about how it’s not going to be full resolution. It’ll just be a bit ‘fuzzy’ - kinda like if you’ve ever tried to output your computer desktop onto a tv through svideo. Still, fuzzy is better than nothing at all.