After years of saving money, finding the best crew, and refining your filmmaking skills, you finally produce the short film that will prove your talent as a filmmaker. Unable to wait for festivals or other distribution, you want to share your work with the world immediately by putting the movie on the web. But what ends up online is not your beautiful 16mm film, but something the looks like it was shot with a PixlVision camera with a shattered lens; the actors’ performances now sound like police walkie-talkies; and it still takes twenty minutes to download the whole thing.
This example may be a little extreme, but it’s not that far from what many filmmakers experience when putting their films on the web—the internet’s promise of widespread distribution comes at a price of image and sound quality. Still, the internet does hold great promise as a way to share video with collaborators, friends, and a worldwide audience, but one must first master the complexities of preparing media for the internet—a process called compression. The last few years have seen the development of mature tools and processes for compressing audio and video that the independent maker can pick up without having to have a degree in engineering.
The biggest limitation to watchable video on the internet is bandwidth, the potential amount of data that can be transferred between points of the internet. Digital video files require a huge amount of bandwidth since they are very large. A five-gigabyte file may not seem like much, now that computers come standard with hard drives of twenty gigabytes or more, but the internet moves data like a dripping faucet, compared to the reservoir of your computer’s hard drive. The typical home user, even with a DSL or cable connection, does not have nearly enough bandwidth to download a full-screen, high-quality video with little compression. To solve this problem, video files need to be compressed so that they are small enough to download and play on a user’s computer.
Compression is not just a simple shrinking process, though; it is a field that draws upon both aesthetic and technical skills to deliver the smallest file that still retains the quality of the original media. It is fairly easy to create a large, slow-to-download file that looks good, or a small, quick file that looks degraded, but quality compression is a balance between squeezing the file size and still retaining the qualities of the image and sound that make the clip worth watching in the first place.
At the most basic level, compression is a manipulation of video data files using software that reduces redundancies within them. But in practice, the successful compression of video starts earlier, when a compressionist changes the aesthetic characteristics of a clip to make it look better once it’s been treated with the encoding software. These steps include blurring, color correction, and cropping. Ideally, compression will factor in earlier in the production of web-destined video, because there are shooting techniques that are helpful to the encoding process, such as shooting on a tripod instead of handheld.
Once a video’s image has been altered, the process of compressing the video file’s data is accomplished with codec software. A codec —which stands for COmpressor/DECompressor—is a piece of software that analyzes the data of a video file and reduces redundancies within it. A codec is usually a piece of a larger video format. For example, the Sorenson Video codec is a piece of the QuickTime format. Most QuickTime-format video on the web is encoded with the Sorenson codec.
Codecs and the science of data compression are not easy topics for most filmmakers to comprehend. Fortunately, compression software takes care of much of the difficult work. There are two general types of software for video compression: Plug-ins and compression features that are added to video editing software, and specialized compression programs designed for people who prepare internet media on a regular basis. Which is best for you will depend on many factors, but mostly on how much control you want over your compressed media.
The current versions of most video editing programs include some export settings suitable for internet delivery. These output modules usually offer a few simple settings designed for the compression novice, but they do not offer enough control to create a file that both looks good and is quick to download. If you don’t expect many people to view your work and don’t think they will mind waiting a little longer for a download, then exporting directly from an editing program can be just fine. People who expect their work to be viewed many times and want the best experience for their audience will need to consider a separate compression program.
There are not many compression programs available. The two most popular are Cleaner (see sidebar review) and ProCoder (Conopus, $699). These two serve as one-stop programs for encoding all the major formats. There are also other programs that encode for just one type of format, such as RealOne Producer for RealVideo, Windows Media Encoder for Windows Media, Sorenson Squeeze for QuickTime, and Wildform Flix Pro and Sorenson Sqeeze for Flash MX video.
Cleaner and ProCoder are designed for users who need total control over all their encoding settings, and also include specialized tools to automate the process of compressing many clips into different formats and settings. These programs are a good choice if you foresee a need to constantly encode a large number of video clips. If you are planning to encode just a few clips, you can get away with using one of the cheaper, single-format programs. Since those programs support only one or two formats, find out ahead of time what format you will need to distribute your film in and then select the appropriate software.
Once you have chosen your encoding program, you’re going to need more reference help than any manual can provide. The best guidebook is Ben Waggoner’s Compression for Great Digital Video (CMP Books, $49). Waggoner claims to be the “world’s greatest compressionist.” I don’t know if that’s the case, but his book is a great resource for anyone who would want to challenge him for the title. The book performs the seemingly paradoxical act of being very readable while going into incredible technical detail. Wagonner leaves no subject untouched and explains such diverse topics as how eyes and brains interpret images, a few notes on information theory, how TV’s and VTR’s work, as well as information about preparing video for the internet. Although a little pricey, the knowledge contained inside the book will make a huge difference in the quality of your online video.
The process of video compression is quite different from filmmaking. Don’t worry if you feel out of your league when trying to prepare your media for the web. The best advice I can give is to look at what’s already available on the internet—check out the leading vendors of online video, and notice the quality and loading times of their clips. Experiment with your own media, making several versions at different settings—which is exactly what professional compressionists do to find the best settings for each clip.