In these days of free, consumer-level video-processing tools such as Windows Movie Maker, it may seem pointless to invest time and effort in learning to use an open-source package such as VirtualDub which, at first glance, appears complex and far from user-friendly.
But when you just want to do a quick editing or transcoding operation, and don't want to wait three days for Windows Live Essentials to download and install, VirtualDub is the perfect alternative. It offers several valuable features that other packages lack, and helps you get quick results without any fuss or patronising wizards.
In its current guise it's just a 1.6MB download - it doesn't even need to be installed: just unpack the ZIP file on your hard disk and run the executable directly.
What can VirtualDub do?
VirtualDub started life as a video capture utility, back in the days when camcorders and video sources were normally analogue and you needed a dedicated video capture card to digitise the analogue source for your PC. Today, that function is redundant for most of us, as modern camcorders produce native digital files. Getting video onto your computer thus becomes a simple matter of plugging the camera into a USB or FireWire port and dragging the files to your desktop.
But that still leaves VirtualDub with three important uses: basic video editing, processing and recompression into different video formats.
When it comes to editing, one of VirtualDub's most useful features is the direct stream copy function. It's useful whenever you need to make edits to a video that's already been saved to a compressed format, such as MPEG. For example, say you want to take a clip from the middle of the file. Other (supposedly more user-friendly) editors will insist on recompressing the clip once you've extracted it, even if they're saving to the same format as the original file. But VirtualDub allows you to make basic edits - cropping and cutting scenes - and save the file back to disk without needlessly decompressing and recompressing it.
This is a boon for two reasons. First, it saves the video from generational degradation: decompressing from a "lossy" video format and recompressing will inevitably reduce its quality. Just as importantly, though, it also saves bags of time. You'll appreciate this if you've ever tried to make a quick DVD edit with Windows Movie Maker and ended up sitting for an hour staring at a compression progress bar.
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| Virtualdub helps you get quick results without any fuss or patronising wizards. |
It works the same if you want to join together two video files: as long as they're in the same format, with the same resolution and frame rate, VirtualDub can splice them together into one seamless video without recompressing them. Direct stream copy also works for audio, as you'll see if you take a look at the video conversion walkthrough on the next page.
Another distinctive feature of VirtualDub is the ability to produce a video file from a series of still images. This gives you a completely free way to get into time-lapse photography and stop-motion animation: your camera or capture device doesn't need to have a specific time-lapse or stop-motion mode. Give VirtualDub a folder full of files and it will combine them and spit out a video file.
If you're interested in software development, VirtualDub is also noteworthy for being one of a few modern applications to include hand-written assembly language in its code. Writing speed-critical sections of a program in native machine language - as opposed to a higher-level language such as Visual Basic or C++ - was common practice a decade or two ago, when computer processors were tens of times slower than they are today. But nowadays, programmers habitually rely on clever compilers to optimise their code for them.
Indeed, the jury is out on whether trying to optimise machine language code "by hand" is really a good idea in today's world of branch-prediction and speculative-caching processors, where it's all but impossible to anticipate exactly how the CPU will process a particular routine. But the fact remains that VirtualDub is very fast when it comes to time-consuming reprocessing and transcoding of video files.
That brings us to yet another of VirtualDub's strengths: transcoding. It can, for instance, read the 5GB+ of VOB files from a DVD and convert them into a more advanced compressed format, such as DivX, to produce a file of about 1GB with little loss in quality. VirtualDub doesn't include the MPEG2 decoder to work with VOB files by default, but its abilities can be extended with plugins, and you can find one suitable for you via a simple web search.
Note, though, that strictly speaking, it's illegal to use this method to archive or recompress commercial DVDs. It is useful though for converting things like wedding DVDs, or videos of your local sports team.
Step by step screenshot walkthough: click below for the next page...
