Alpha Images

[shoutcast101]

scvi.net has been very useful to me. However I want to add a logo to my images as shown in this tutorial:

Nullsoft Video © Information

Adding graphics to NSV files
Written by ken52787
Edited by Sankt

This is a guide for adding logos to new video, not existing NSV files. You must re-encode existing NSV files to add logos to them.

Step 1.
Make a logo in Adobe or similar graphics program. Unless your logo is a solid square, you will need to open a alpha channel.

There are 2 ways to do this.

* use a black background
* create a separate picture with grey as an alpha channel

The first method is the easiest. If you have any other black in the logo, that'll disappear using this method. The second method requires making two images, both this same size. Use grey in areas that you want transparent on the first image. Save the images as a targa (tga) or bitmap (bmp).

Step 2.
Get virtualdub (www.virutaldub.org for the official site, or fcchandler.home.comcast.net/stable/VirtualDub-MPEG2.zip for a version that allows you to use MPEG2). Open it up and load up your source video. Go to Video > Filters, and click Add. Double-click logo and load your image. Check the alpha option. Use premultiplied alpha if you did the black background solution, or the other Alpha image option if you made that separate file.

Set the opacity low if you want your logo slightly transparent. Adjust the justification settings to get it in the right area. Press OK.

I find it much easier to do all the resizing and deinterlacing, etc in VirtualDub (instead of nsvenc).

Step 3.
In the video menu, go to compression. Select a codec to make the temp video for NSV encoding. There probably will be VP3 and VP6 options, but don't use those. I personally use Uncompressed (even though it is huge) for it's speed. Cinepak on 100% quality is smaller, but still rather large. I'd recommend staying away from codecs such as Divx. When selected, go to File > Save as AVI

Step 4.
When complete, encode this new AVI in your favorite NSV encoder and delete that giant AVI file.

As you can see from the image, this concept can be used for other things. For example, I'm adding a very large message asking for relays.

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However I cannot find a tutorial which shows how to make alpha images. It can be in any popular graphics program (I have demo copys on cd!). Photoshop, Photoshop elements, Paint Shop pro, Ulead Photo Express, The GIMP, Photoimpact, CorelDraw 11

[sankt]

www.mankua.com/psdocs/psp_tut.htm

www.simtrainz.com/vulcan/tutorial2.htm

[shoutcast101]

Looks great I will try it out now.

[shoutcast101]

Sorry I still don't get it! Are there any more basic tutorials?

[ken52787]

There are 2 ways to do this.

* use a black background
* create a separate picture with grey as an alpha channel

The first method is the easiest. If you have any other black in the logo, that'll disappear using this method. The second method requires making two images, both this same size. Use grey in areas that you want transparent on the first image. Save the images as a targa (tga) or bitmap (bmp).

follow this. for example, in the first one, use black as if it were the transparent part

[shoutcast101]

ken52787, when I do this virtualdub says that filters cannot be started because there is no alpha channel.

[shoutcast101]

sankt, I went through the tutorial again and I have not got it working using tgatool. Thanks

[shoutcast101]

This is really weird. For some reson alpha is only working on some of my avi's why is this?

[shoutcast101]

To show you what I mean I will attach some avi files. I can only attach one per post so I will post two files This one is named a txt so it will work when adding a logo in virtual dub. Download it and rename .avi. THIS file WORKS. Then next file does not work in virtual dub when adding a logo. Both avi's use the same logo and settings.

[shoutcast101]

Part two. THIS FILE DOES NOT work with logo. I have had to zip it up. rename .zip to .txt

[shoutcast101]

Anyone

[shoutcast101]

Fixed it!