This guide will explain how you can use Avisynth
to create overlays and other video processing. These methods will allow you to
transfer graphics straight from the source
files to NSV without the need to create any temporary video files.
You need to get Avisynth. You can download it from www.avisynth.org. The overlay part of the guide also requires Adobe Photoshop.
Other image editing software may be compatible.
This guide also assumes you have a good understanding of video files and
terms like resolution, framerate, etc.
If you are going to use Divx or Xvid video, you need to get the latest Divx codec
from www.divx.com. Install the
software, then go into the Decoder Configuration Utility. Under
the quality settings tab, make sure "Support Generic Mpeg-4" is selected. It
also is a good idea to select "Disable logo" because that will show up in your
encodings.
Resizing and changing framerate.
Open notepad and then save the file. Make sure the "Save as type" is set to All
Files, then call it "example.avs". This will be our script file.
Open a video file by typing the following line, substituting in your
video's path :
DirectShowSource ("C:\path\to\video.avi")
Save the file again and open it in Windows Media Player (you will have to set
the File Types to all to select it). If all went well, it should start playing
your video.
Now resize this video using a Bilinear filter to avoid jaggies.
In your notepad, add this to your line :
DirectShowSource ("C:\path\to\video.avi").BilinearResize(320,240)
Now watch the file again and it should have been resized to 320 x 240.
You also might want to change the framerate of the video so that you can get a
more efficiently compressed video when you encode it to NSV.
You can do that by adding a new line to your script, with this in it :
ChangeFPS(15)
This will convert the framerate to 15fps.
You can visit www.avisynth.org for a whole list of other filters you can apply, but
one more that I will share that I like to use is the Temporal Softener. It will
help get rid of noise, which can be hell on encoding.
You can apply it using :
TemporalSoften (4,4,8,15,2)
Overlaying a station watermark
Here's where things start getting a little tricky. First off, this is when we
start dealing with several sources (the video and the images for the overlay) so
we need to start naming the sources. We do that by a simple "name = ".
The loading of the video in our script now becomes :
video = DirectShowSource("C:\path\to\video.avi").BilinearResize(320,240)
Make the image to overlay.
You need to launch Photoshop (or similar
image editing software.). Start by
creating an image with the size of your planned video output (ie. 320x240). This
allows for easy positioning as you can do it right in Photoshop. Make sure the
background is transparent. Now create a logo, for my example, I'll use a simple
shape with a spray behind it. You can make it as complex as you want. This guide
will allow you to have transparences (even partial transparencies) in your
image, so go all out.
| Example
image :
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Now add a new layer, and drag it all the way to the bottom of the layer list.
Make sure that layer is highlighted, then use the paintcan to fill the entire
layer in with black. Its ok if you can't see the black parts of your logo
anymore, they will show up in the video.
| Example image :
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