Rotating and Cropping a Video Scene
Having always used movie cameras and camcorders in the upright position, I hadn’t realized how many turn them sideways to get a portrait-mode video clip, or create/receive clips that need rotation. Movie Maker can rotate clips by 90 or 180 degrees, but it results in mishaped and/or black borders… and sometimes you need something other than a 90 degree turn.
rotating scenes as needed, and cropping and resizing to appropriately resize the content to fill the screen. It’s something that’s easier to do than to explain.
As I videoed my grandson’s football game on Saturday, I forced myself to take a couple scenes at angles that would need correcting during editing… to get a couple real clips to use for this tutorial.
Here’s a frame from each of 4 scenes as they look in VirtualDub. Two are normal. One needs a 90 degree clockwise rotation, and the other needs turning about 45 degrees clockwise.
I’ll open the same file in both Movie Maker and VirtualDub, and move back and forth between the two apps as I work on the selected segment. They don’t conflict.
I took the footage in widescreen mode. I’ll use the widescreen option in Movie Maker, and the images will appear a bit squeezed in VirtualDub… ignore the squeezing and all will be fine. VirtualDub doesn’t reshape pixels to maintain the aspect ratio as Movie Maker does.
… before getting into it, here are a few notes…
My Toshiba laptop was officially declared a ‘lemon’ by CompUSA last week. Three days after being returned from the last repair trip, it needed a new mother-board (again). As it was under a 3-year extended warranty, I was able to select anything up to the original purchase price to replace it; an HP laptop is on order.
I’ll be at the Microsoft MVP Summit next week, and doing some vacationing on the way back… traveling with my old Dell laptop while I wait for delivery of the new HP. Being cramped for time and computer capabilities, I’ll publish this and the next issue #72 very early, and then skip a week before #73.
…. on to the main topic
Rotating Selected Scenes with VirtualDub…
Older versions of VirtualDub don’t handle the newer type I DV-AVI files from Movie Maker 2 but VirtualDub 1.6.0 (build 215490) does. With the Panasonic DV codec installed on the computer, it’s easy and lossless to go back and forth between Movie Maker and VirtualDub during project editing.
When Movie Maker has a file open, it doesn’t lock it from being used by other software… and VirtualDub acts the same way. One result is being able to use Movie Maker and VirtualDub with the same file at the same time.
I’ll emphasize this point as we go, starting by showing you the screen shot at the right… with the same source file open in both software apps.
When you see a segment that needs rotating, select the segment in VirtualDub by marking its first frame (press the Home key) and last frame (press the End key)… that tells Virtual Dub to use that segment when rendering a new file with your changes applied.
You can apply rotation and cropping filters at the same time, but I prefer doing them in two steps… rotating the segment first, and then cropping while looking at… the clip rightside up.
For this rotation, after selecting the range in VirtualDub, apply the rotate2 filer with a setting of -47 degrees, select the Panasonic codec for video compression, and then render the segment to a new file (File > Save as AVI). There’s no need to resize; it’s DV-AVI in and DV-AVI out… and DV-AVI (NTSC) is always 720×480 pixels.
Leaving VirtualDub open, import the new clip into Movie Maker and see how it looks… I named it a temporary file because I knew it would need cropping also… unless you like this kind of black-border effect, in which case you’re done.
Preview the rotated clip in the MM2 collection and note that its made from just the selected segment of the larger clip.
… Leaving MM2 open, go back to VirtualDub, this time to crop the rotated clip to show the center of interest… and resize that part to the full 720×480 pixels.
Add the resize filter (Video > Filters > resize). Opt for 720×480 for DV-AVI (NTSC) size…
The Cropping option isn’t a filter in VirtualDub… it’s an option that you can use when adding any of the filters.
It’s grayed out until you add a filter. In this case, adding the resize filter ungrays the button.
Pressing the Cropping button opens this window… where you tweak the 4 controls to get the desired offset dimensions.
Many scenes such as this one don’t need precise arithmetic. I eyeball/estimate it as I set the cropping lines. When it looks OK, press the button and move on.
With the cropping settings selected, the resizing ready to make it 720×480, the Panasonic DV codec selected for video compression, save it as an AVI file (File > Save as AVI), and you have what should be the final corrected clip.
… from VirtualDub, go back to Movie Maker 2, import the new clip and take a look at it in the preview monitor.
If it’s good enough, put it into your project and keep going. If you want to tweak it further, it’s still an open project in Virtual Dub… go back and adjust the settings some more, and save it again to a new avi file.
Here’s the rotated, cropped and resized clip in Movie Maker…
Check the clip’s audio track. The wave patterns show the audio track made it through the two rendering processes without us having to think about it.
That’s all there is to it.
Conclusions and Closing
I’m hoping you’ll find the process of using Movie Maker and VirtualDub together like this to be easy and fun…
I didn’t go through the other scene that needed rotating… it would be even easier than the one we did. Use the rotate filter instead of the rotate2… Rotate is for 90 degree increments… rotate2 is for any angle.
If you don’t take videos at angles and don’t need to rotate clips, you can get lots of mileage from the cropping feature… I’m sure there are many scenes where you would like to change the focus of attention by cropping/resizing.