Digitizing Video
An Introductory Course by Kirk Pearson
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Unit
One:
Introduction to Digital Video
Unit
Three:
Computer Readiness
Unit Five:
Video Capture & Editing
Inputting Footage
Given the processor-intensive nature of digitizing video, it would be wise to do some housekeeping on your computer ahead of time, a little tuning as it were. Typical activities you probably already do periodically such as deleting unused files and programs, running diagnostic and maintenance utilities such as Norton Systemworks, and defragmenting hard drives should be done before getting underway. You should also set up an area (or whole drive) and directories to separately house the projects you intend to take on. A couple of the many sites offering helpful information in the area of computer maintenance are 'TheallIneed.com' and '5starsupport.com.'
Hopefully by now you have your hardware and software in sync, your computer tuned up, and you have all necessary cabling and connectors to physically hook your input device up to your computer. If so, you are ready to get started. Since this is a generic course on digitizing video and I don't know exactly what software you are using, you'll have to rely on its particular 'wizards' (if available), help screens, and documentation for specifics. Some advise having your input device powered up before you start your computer to ensure that it is properly recognized and that the appropriate drivers are loaded. You will then start your program and open its capture interface.
When capturing footage, there are a number of options that you may be presented with, particularly if starting with analog video. We've previously discussed video format (or codecs) and resolution in earlier units. At this juncture I might add that DV format shares a resolution of 720x480 pixels with MPEG-2, the one commonly used with DVDs. And if DV video is selected as the capture format, it has a preset resolution that you cannot adjust. MPEG-1 captures at either 320x240 or 352x240 pixels depending upon the device used for capturing (the latter resolution being more appropriate for VideoCD or SuperVideoCD, video formats for use with CDs popular before DVD players became affordable). For more information than you really want on pixels and resolutions try 'Lurker's Guide to Video' and select the 'How Big is Video?' link.
Frame rate refers to the frames per second that are stored when capturing video. For the common formats (MPEG-2, MPEG-1, and DV video) the default is 29.97 to coincide with the NTSC standard for televisions. For other formats you may be able to choose alternate frame rates if there is a reason to do so (uncommon). In a similar manner, video data rate refers to the amount of data stored per second. If capturing in DV format this is a preset valued at 3.6 MB/sec, while MPEG-2 and -1 are scalable and can be adjusted.
There can also be settings for audio format and data rate during captures. Audio format is typically MPEG or if left uncompressed, is saved in some type of PCM (Pulse Code Modulation) format. (It's a little technical but if you'd like to learn more about it try PCM1 or PCM2.) Audio data rate is often set when you select other capture parameters but if left uncompressed, CD-ROM quality sound is usually preferred (this involves a sample rate of 44 kHz or 44K per second, in 16-bit mode for stereo which results in 176K/sec total audio data rate).
Other concerns with capturing analog video may include signal tuning for factors such as color, brightness, and audio volume. Depending upon the video editing software being used, there may be more or fewer options, and more or less automation to the whole process (remember the 'idiot light' analogy?). You may also have the option of scene detection which means that the software will break the incoming video down into segments based on time codes (DV camcorders) or in some cases content. In the latter, the editor is scanning for significant changes between frames which it interprets as a new videoing session. This doesn't always work right since during the same videoing session you may have moved from one area to another which could be interpreted as a separate session.
Something to watch for are dropped frames. These happen when the incoming
data can't be stored to disk fast enough. The editing software will keep
repeating the last frame successfully stored until the computer catches
up which can cause anomalies in the saved file when viewed. This shouldn't
be a problem with newer computer equipment but may necessitate reduction
in the data rate if older equipment is responsible.
It is generally recommended to begin with a short capture, just a minute
or two, and then stop the capture operation and play the video to test
your settings and view the quality of the captured data. This may necessitate
leaving the capture interface and going into editing but you don't want
to find out after a long capture session that there was a problem which
ruined the project. Similarly, assuming that you've captured at the highest
quality, you may also want to convert your sample to the final distribution
format (if different) and test that as well. Since this involves another
encoding step, you may experience unsatisfactory results that can be compensated
for by changing the capture settings.
Basic Editing
Editing video can be characterized as part art and part science. You've been getting a healthy dose of the science end of it with hardware and software issues, and although editing entails some science too, it is where your artistic flair will come in. The fact is, once you have successfully captured your footage (and if you began with analog material), you have already digitized your video. Editing is where you forge your footage into something entertaining and unique. As such, a course like this can take you only so far in regard to this area and the rest will be up to you. Over the next two units we'll take a brief look at the three main aspects of video editing: clip trimming/splitting, transitions, and titles.
With the 'artsy' caveat aside, whether you utilized scene detection during your capture or not, you will begin by examining your individual scenes or clips and begin organizing your 'movie' or project. This may involve splitting or combining clips, removing some altogether, importing others, revising individual clips, etc. The storyboard was mentioned earlier in the course and is designed with this process in mind. The overall goal is to create clips/footage that have a high content and relevancy to your project's purpose and that allow for multiple transitioned sequences rather than a few that are long.
Some generalities to keep in mind are that while you make your changes, most editors preserve the integrity of the initial capture file and save your work in a separate project file. Unless you unlock them, audio and video tracks of each clip will remain together and synchronized. There are usually undo/redo functions which should help to take some of the intrepidation out of the process, and there should continue to be varying levels of automation/presets that are applied by default (such as transition length) so you can ease into more responsibility as you feel ready.
Most editors will allow you to switch back and forth between the storyboard (Windows Movie Maker 2 example) and timeline (Windows Movie Maker 2 example) environments. The latter will be needed whenever you need to see the audio and video tracks separately and/or are interested in exact timing of effects. The former is a more visual representation of how your 'story' will unfold and how well it flows. As you complete your project, it may be advantageous to pay attention to various TV or movies you see and note how the video flows. How are shots varied or positioned? What about transitions and titles? How often do things change and how well is your interest kept? You'll probably see that variety and change are basic elements in video production and are what your target viewers are used to.
As discussed in the Software unit, there are a variety of tracks to work with. You may have more than one for video, and will probably have at least two or three for audio. One is dedicated to the sound that accompanied the video when acquired. The others can be used for background music, sound effects, narration, etc.
It is generally recommended to perform video editing tasks in the following order: clip arranging/trimming, transition and title additions, special effects (if any), and audio additions. This is advised to keep audio in sync with the video. The earlier operations change the position of the video and you want it set/anchored to know where to place your audio portions.
Try to keep a vision of the overall project as you perform your editing tasks (and I might add, the next time you shoot video). Since you undoubtedly plan to use some transition effects, when you are trimming your clips you will want to leave a little video at the beginning and end of each clip that will be preceded or followed by a transition to avoid the transition cutting off video or sound that you intended to include. This can vary but a second or two is usually adequate.
Along similar lines, insert editing (usually available in software with timeline environments) requires a little thought to successfully complete. This is where you are including clips from other video taken and/or are changing the order of clips to produce an effect of more than one camcorder present during initial acquisition. An example would be your nightly news where they keep the newsman turning back and forth between two different cameras to keep inducing change to better hold the viewer's interest. Of course they really do have more than one camera but you can create this effect through thoughtful use of insert editing.
It should at least be mentioned that most video editors have the capability to insert still images as well, and in most cases, even build a slideshow presentation (Ulead VideoStudio 8 example) or short animation with them. Still images are usually kept separately in their own library and tools for viewing and manipulating them are accessed through it. Video editing programs vary on how they display images and it is desirable that they maintain the image's original aspect ratio (the relationship between horizontal and vertical pixels). Some may not and rather stretch images to achieve the aspect ratio which is used for television (after all, it is a video editor) which is 4:3. This simply means that for every four horizontal pixels there are three vertical pixels. The general rule to remember when working with images is leave the original's aspect ratio alone and when cropping or trimming, use the 4:3 ratio for the best, undistorted display on a television.
Slide shows are similar to putting together a music video in that they are a collection of clips (images in this case), joined by transitions, and are typically set to background music. Editors vary in their handling of these tasks with some automating a significant amount of the process. Some editors may also be able to create video from still images by digitally panning and zooming in and out of the picture. And some allow the ability to overlay text or other images. For the most part though, to create these types of presentations easily and with more pizzazz, you will be better off with a program designed to do this or at least you may need to step up to the prosumer-level of editing software.
This section has provided some basic editing background that should be common to most mainstream video editors. There are differences of course, and exactly how the editing tasks are performed is part of what separates one program from another. This should help to get you started and encourage exploration of your particular package's features and how to access them.
Audio Considerations
Audio and the effects that can be applied to it through the video editor are an important dimension of the editing process. Most programs allow the addition of audio tracks which can include narration and external music files. Some also include audio files for special effects and libraries of thematic music that can be useful if composing a 'music video' of your own.
If you desire to add a narration to your video, you will need a microphone and a headset. (The latter permits temporarily turning off your computer's speakers to avoid feedback or sound from them being picked up by the microphone.) Most computers today have ports/jacks on the front and/or back of the computer for both of these equipment items, and there are also microphones available that plug into a USB port.
When recording narration, be sensitive to any potential background sounds and take appropriate steps to eliminate them or reduce their influence prior to beginning. It is also a good idea to draft a script or written copy that you'll be reading to ensure a polished product and avoid errors that may require starting over. Of course this isn't necessary in all cases and depends upon your personal speaking experience and ability and your target audience. Be sensitive to timing issues and know how long or short your narration needs to be to fuse nicely with the video that it is accompanying.
When working with files from CD-ROMs, some find that free tools such as RealNetworks RealOne/Player or Microsoft Media Player offer superior 'ripping' features (file conversion/renaming). The preferred formats for importing audio files are WAV and MP3 since they are supported by most video editors.
Working with audio files is similar to video in that the editor workbench/timeline tools for trimming and controlling either are generally the same. Audio track volume can be adjusted and whenever a video transition is applied, the audio can be transitioned as well to match. Through a process known as cross-fading, audio in the first clip is faded away to nothing while audio from the next clip is brought up to 100%.
Prosumer-level editors allow more operations to be done to audio, and consumer-level editors continue to pick up some of their features. Your package may allow for noise removal (background or equipment-related), equalization (like a stereo graphic equalizer, this allows more precise sound frequency control), normalization (set all audio tracks to the same level), or any number of other features. Get familiar enough with your documentation to know what you have in case you need it down the road.
(Images courtesy: BestAnimations.com, AnimationLibrary.com, Images.Google.com)
