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| How
to make the background transparent in your Wild
FX Pro video titles |
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| Contents |
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| Top |
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| Introduction |
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| Many
people want to create video titles with transparent
backgrounds so they can then import them into their
non-linear editing system and overlay the titles
onto existing video. You can do this using Wild
FX Pro. This brief tutorial contains some information
on this. Since every non-linear editor works a
little differently you will need to work with the
imported files differently depending on the software
you are using. |
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| Alpha
channel |
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Probably
the best method for creating transparent backgrounds
in video is to use an alpha channel.
Images represented on video are composed of three
grayscale images called channels – one red,
one green, one blue - or RGB images. An alpha channel
is a fourth channel in an RGB image that defines
what parts of the image are transparent or semi-transparent.
An alpha channel can be either straight or premultiplied,
depending on the program that created the image.
Wild FX Pro uses the straight alpha channel. When
an image contains a straight alpha channel, the
transparency information is stored only in the
alpha channel.
When you select the transparent background option
in the Video tab you activate the straight alpha
channel setting in the graphics mode of your output
video. |
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This
enables you to use the alpha channel setting if
you select an output codec that supports alpha
channels. If a codec which does not support alpha
channels is used, the alpha will be lost in the
final output. By adding an alpha channel, you can
bring the video into a video editing software that
supports alpha channel to make the background transparent.
The option to use an alpha channel will only be
available for output video codecs that support
alpha channels. We advise using a Quicktime MOV
or AVI output preferably with no compression (codec="none")
or with a codec that supports transparency.
In Wild FX Pro when you select the “Options” button
at the top of the Video tab it will open the Movie
Settings window. The Movie Settings Window tells
you which codec you have selected. |
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Selecting
the the “Settings” button opens the “Compression
Settings” window.
Here you can change the codec you have selected.
In Wild FX Pro you can use any codec you have installed
that runs through the Quicktime system on your
computer. (Make sure you have the complete “Recommended” install
of the free Quicktime player to output video.) |
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The
Quality slider that lets you set the output video
quality. Better quality equals larger file size.
For video titling I will select “Best”.
There are also options to set the:
- Frames per second: this
determines the output video framerate. Remember
that this is not the same thing as the effect
framerate that is set in the Main tab. (As
a general rule you want your effect framerate
to be a factor of your video framerate. So,
for instance, if your video framerate is 30fps,
you will probably want to set your effect framerate
to 10, 15, or 30.) If you are planning on bringing
your Wild FX Pro output into another project,
you will want to match the framerate of your
project.
- Key frames: Compressed
video frames are defined as "interframes" or "intraframes".
Interframe means many frames are described
based on their difference from the preceding
frame. Intraframe means each frame is compressed
separately and independent of surrounding frames
(for example, JPEG is an intraframe codec).
If you use an interframe codec it will utilize
intraframes, which are the "keyframes",
or reference frames, that are used to generate
the interframes. For working with Wild FX Pro,
you will probably want the best quality and
you will want every frame to be a keyframe,
so you leave it unchecked, or set a value of
1. Higher values result in lower file sizes.
- Limit data rate to:Here
you can set the bitrate of your output video.
For working with Wild FX Pro, you will probably
want the best quality and you will not want
to set a limit to your data rate so you will
leave this unchecked or set a very high number.
Higher values result in larger file sizes.
If you select the Options button, it opens the
Encoder Configuration window. For Indeo this contains
the Transparency setting. |
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Using
the dropdown menu on the left you can select “First
Frame Analysis” as the transparency mode.
The following formats/codecs support the use of
alpha channel transparency through Wild FX Pro:
- MOV: Animation, None (uncompressed),
PNG, TGA, TIFF, Indeo (For more information
on Indeo codecs, check out: http://www.ligos.com/indeo.htm.)
- AVI: None (uncompressed)
- Image Sequences: PNG, TGA,
TIFF
NOTE: The color depth option (if
it is available) must always be set to " Millions
of Colors+" to use alpha channel transparency. |
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| Keying
out the background |
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Another
method used to make the background in video transparent
is called keying – you key out the background
color and make it transparent. You can use a key
in your non-linear editing software when your video
has a solid background color that makes it easy
to distinguish from the foreground.
There are many different types of keys. Here are
some of them:
- Chroma Key: Chroma key lets you select a
color in a video clip to be transparent.
- RGB Difference: The RGB Difference key is
a simpler version of the Chroma key that allows
you to select a range of color.
- Luminance key: The Luminance key creates
transparency for darker values in the image,
leaving brighter colors opaque.
- Black and White Alpha Matte keys: These
are used to key out a black or white background.
- Blue and Green Screen keys: These are used
to key out blue or green screens (true chroma
blue and green).
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| Use
a solid background |
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| You
will need to use a solid image background color
(preferably black or white) without any gradient
or image fill to use the alpha channel setting
or if you want to key out the background without
using the alpha channel (see below). |
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| Working
with non-linear editors |
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| Once
you have brought the video title into your non-linear
editing software there is typically some method
used to activate the transparency, so the program
will know to make the background of the selected
video transparent. Each software is a little different
in how transparency is handled, so you will need
to consult the help manual for each product to
determine the exact method. |
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| A
note on using Wild FX Pro’s transparency
setting |
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| Adding
an extra frame: Many of the effects in Wild FX
Pro have elements in them which can appear on the
first frame of the output and throw off the alpha
channel setting. Consequently, Wild FX Pro automatically
adds a single frame to the beginning of the output
if you have selected the transparent background
option (Video tab). If you do not want to have
this extra frame added, you can select the "Remove
extra frame from transparent video output" in
the Options window. |
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| A
note on Wild FX Pro’s SWF output transparency |
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The
.swf output from Wild FX Pro will have a transparent
background unless you:
- set the background to be opaque (Choose BG
Fill window).
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- combine the fade in or fade out features
(Video tab) with the text stroke, text gradient
fill or text image fill options (Main tab)
which will disable the transparency of the
background of the output .swf file.
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| For
further information on how to use Wild FX Pro,
please see our Creating
high quality digital video titles with the Wild
FX Pro Video Titler & Text Animator tutorial. |
