Detonation Films & LumaKeying

[Tyler2000]

I downloaded the free stock footage at http://www.detonationfilms.com/free_stuff.htm.

I can use the chromakey script in AviSynth for the blue and green background videos, but I think I need something different for the videos in the dark. I have heard of luma keying, but I'm not sure what it is. Would luma keying block out the dark areas and only show the light areas? Where can I find a lumakey filter for virtualdub or a script for Avisynth?

Detonation Films says to use a "screen transparency for compositing". I think they are talking about Adobe Premiere, but I don't have that program.

[dipstick]

Thank's for the link.

I can't really help you find a Lumakey filter for Virtualdub. I downloaded one of the dark background explosion clips and played with it in Premiere. I used the Luminance key filter to adjust the transparency. It worked out great. You can check it out on this little clip I made with it:

attack.wmv

The picture of the planes was made for this effect.

Most any good NLE that supports multilayers and transparencies should work for this. If you don't have any, You could output the explosion only to image sequence in Virtualdub. It should only be 5-10 frames anyway. You could then edit them in Photoshop to delete the background. You will still need a way to overlay them on your video. You can use Wax2 for this. Save your images as psd or png with transparent background. Set the time of each image as desired and use the "Quick 3D" plug-in to move them into the position you want.

Good luck!

P.S. This post would probably be better.........and get more attention in Editing Cutting and Joining Forum.

[Tyler2000]

I have been trying to figure out AviSynth.

I used this script:

clip1 = AviSource("base.avi").converttorgb32()
clip2 = AviSource("DirtHitLuma02.avi").converttorgb32()

Layer(clip1,clip2,"lighten")

The video I'm trying to overlay is a puff of smoke. The transparency looks natural with this script, but the smoke looks green when it should be brown.

[Tyler2000]

Should I start a new topic in the Editing, Cutting and Joining Forum or should I wait for a moderator to move this topic there?

[dipstick]

It looks like your gaining some ground. I'm not much of an Avisynth geek (I only use it occasionally) so I cant help too much there. The good news is that there are quite a few Avisynth geeks in the other forums.

Go ahead and start another thread. Use a different tittle like, "How to set transparency with Avisynth?" or "Avisynth & transparencies?"

It's worth a shot. Maybe someone with much more experience with Avisynth can help. If the moderators don't like it, they can close this one.

[Tyler2000]

I have it working now, but I'm not sure why. It seems to work better on some backgrounds than others.

clip1 = AviSource("background.avi").ConvertToYUY2
clip2 = AviSource("foregroundexplosion.avi").ConvertToYUY2

Layer(clip2,clip1,"lighten")

[dipstick]

It's great that you've got it working.

If you feel like it, upload a short clip you create. I'm curious what kind of quallity you can get overlaying alpha channeled clips with Avisynth.

The only thing I use Avisynth for is when I want to split the fields of an interlaced DV file. I never thought of using it to overlay clips.

[Tyler2000]

boom.wmv

[dipstick]

Very cool!

I'm surprised you could do all that wih Avisynth. It must have taken lot's of script writing. It just shows that pusistance realy does pay off.

I like the effect.