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Thread: Need help making the black background transparent after keying

  1. Default Need help making the black background transparent after keying

    Greetings,
    I shot in front of a blue screen, then used garbage matte and blue keying to remove the blue background, then I rendered another avi. When I put the avi on the timeline with the final background and logo, I ended up with a black background and I can't remember what I did to make the black background transparent when I used this same technique 9 months ago.

    Here's how I arranged the tracks on the timeline: Video 2: TV studio background; Audio 2: audio.avi; Video 3: video.avi; video 5: HT logo.


    Here's a screenshot of the timeline. Can anyone tell me how to make the black background transparent so that I appear to be standing in the TV studio?
    Thanks, Antoinette

    Attached Images Attached Images

  2. #2

    Default

    When you key footage you need to export to a codec that supports alpha channels in order to preserve the transparency when you re-import. It's > 15 years since I used AVI, which is a container, not a codec, so I have no idea what codec you're using or have available.

    If you have pure black then you should be able to use a luma keyer to get rid of it, but be aware that any our black within your subject will also be keyed.

    I'm not sure why you exported the file in the first place, instead of keying than then overlaying. Perhaps you could share your workflow with us so we can see if we can help you optimise is a little?

  3. Default

    Quote Originally Posted by David Partington View Post
    When you key footage you need to export to a codec that supports alpha channels in order to preserve the transparency when you re-import. It's > 15 years since I used AVI, which is a container, not a codec, so I have no idea what codec you're using or have available.

    If you have pure black then you should be able to use a luma keyer to get rid of it, but be aware that any our black within your subject will also be keyed.

    I'm not sure why you exported the file in the first place, instead of keying than then overlaying. Perhaps you could share your workflow with us so we can see if we can help you optimise is a little?
    David to the rescue!

    Hi David, I exported and reimported the avi so I wouldn't have a bunch of clips to move from the track where I originally edited them to Track 3 which allows me to lay other tracks beneath. After reading your response [instead of keying than then overlaying], I opened the PREL file that has the original keying, selected each segment of the original, keyed file and grouped them. Then it was easy to move the grouped file to Track 3 and lay the background on Video 2... and - voila - the background is now transparent. Thank you; when you've been away for a while, it takes some help to get re-oriented quickly. I really appreciate your help.

    P.S. I'm chronicalling the steps that work so I can have a proven workflow to speed myself along from now on. Again, thanks.

  4. Default Matte Rendered in the Wrong Place

    HI David and all,
    Here's an issue that has me completely puzzled; I followed your advice as mentioned above and layered the original, keyed file on the timeline. Everything looked good so I rendered it as a wmv file and the finished file looks like the garbage matte is in the wrong place. The image on the left is a screenshot showing how the file looks intact on the timeline; the file on the right is a snapshot from the rendered file.

    Any idea why the file would render with the matte in the wrong place when it looks perfect on the timeline? I checked the 8 point garbage matte across all clips and it frames me
    perfectly in every clip.

    Attached Images Attached Images

  5. #5

    Default

    Unfortunately I don't use the same software as you, so you may need help someone one who does.

    However, the very first thing I would do is delete any render files you ay have created. Occasionally render files can screw up exports. Failing that, save the project, reboot and try again.

    If all that fails then try changing the mask very slightly to see if some mask settings are causing the issue.

    But, these are all generic things, some one with the same software may be able to nail it for you in one go.

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