HomePage 3 of 3: Removing Alpha-Blended Logos
Removing Alpha-Blended Logos
This section shows you how to remove alpha-blended (semi transparent) logos, which are usually harder to remove with acceptable quality. This process is a bit more advanced, and you will certainly need a bit more skill when it comes to editing bitmap images.
Start VirtualDub. Load in the video file that has the logo/watermark you want to remove.
From the "Video" menu, select "Filters". In the window that opens, press the "Add" button and select the "DeLogo 1.3.2" filter, press "OK" to load the filter.
The "DeLogo" filter setup screen should now show up. Press the "Show Preview" button down at the bottom to launch the "Filter Preview" window. Use the slider controls in the preview window to skip to a section of the video where the logo (to be removed) is most visible. For example, in the screenshot below, the logo I want to remove is the "PREMIERE LIVE" logo in the top right corner.
Going back to the main DeLogo window, press the "Save Frame" button (circled below) and save the frame as a BMP file.
Now open the newly saved BMP file in your paint/bitmap editor (leaving VirtualDub still open). What we need to do is to paint over the logo using the red color, leave a border around it with the existing images in the frame, and then paint everything else as blue. First, select the proper red color, the RGB value should be R:255, G:0, B:0 (HTML color code should be #FF0000). Now paint over the logo. Leave a border around the painted logo, and then paint the rest as blue (R:0, G:0, B:255 - #0000FF) - the screenshot below explains this concept a bit better (note the "black" border around the red logo is actually not black, but rather, pixels from the original frame). How you might achieve this depends on your graphics editing software, but I used Paint Shop Pro and what I did was to use the magic wand to selected the red painted area, invert the selection, contract the select by 5 pixels to give me the border, and then paint the now selected area blue (and then cleaning up the unselected areas by painting with blue as well). Save this BMP as another file (you can save over the original, but let's keep it just in case we need to re-do the logo painting later on).
Going back to VirtualDub's DeLogo window, load the BMP file that has the logo painted in red, using the "Load" button in the "Analyse" section (circled in the screenshot below).
Press the "Show Preview" button again. You can select the "Analysis" radio button in the "Preview" section of the DeLogo window - this will show you the analysis mask (red being the area that will be removed, blue being the area that is untouched, and black being the area where some blending might occur).
If the logo does not appear in all frames, you can use the "On Frames" text edit box to enter the frames where the logo does appear, using the following syntax:
- Empty: All frames to be processed
- Single frame value: Only this frame will be processed
- FrameA-FrameB: Only frames from FrameA to FrameB will be processed (eg. "150-200" only the frames 150 to 200 will be processed)
- -FrameA: Process all frames from the first frame to FrameA (eg. "-150" only processes the first 150 frames)
- FrameA-: Process all frames from FrameA to the last frame (eg. "150-" only processes frame 150 until the last frame)
- You can specify multiple frames or regions by separating using commas, for example "-150,175,200-220,250-" (this specifies the first 150 frames, frame 175, frames 200 to 220 and from frame 250 frame onwards will be processed)
Press the "Sample Video" button and select the "All frames" option (this analyzes all frames, so it might take a long time if your video is long - in this case, select "All keyframes" instead).
Click on the "Show Preview" button to display the preview window. You can now click on the "DeBlend" radio button in the "Preview" section of the DeLogo window - the "DeBlend falloff" slider near the bottom can be used to adjust the blurring/blending of the removed logo to its surroundings. Click on the "Standard" radio button to see the preview of what the final (logo-less) video will look like.
You can adjust the properties of the repair mask by adjusting the "Repair parameters" shown on the main DeLogo window.
You can select the "Repair" radio button in the "Preview" section of the DeLogo window to help you see the repair mask more clearly, when adjusting the repair parameters (select the "Standard" radio button to return to the normal preview):
Depths: This is the yellow border around the red repair mask - increasing the depth increases the width of this yellow border.
Power: The lower the power, the more blurred the result.
Interlaced: Enable this when your input video is interlaced, which can improve the processing effect.
Pixel aspect: This specifies the pixel aspect ratio, can be adjusted when the pixel aspect ratio isn't 1:1 - changing this setting affects the border size and shape too.
When you're happy with the results, press the "Close" button to close the DeLogo window. Press "OK" to close the "Filters" window and then re-encode your video, now minus the logo. This guide will not cover the video re-encoding instructions, but you can read a quick reminder of how it's done in our VirtualDub: Two Pass Encoding short guide.
