By the end of this module you should be able to do the following:
Compare and contrast animation with video
Describe how sound is synced in non-digital video
Compare and contrast digital video with analog video
Describe some of the measurements that determine the properties of a digital video file
Video is a series of images flashed in such rapid succession that your eye interprets the changes between successive images as motion. Traditional film works in this manner. Every frame in a 35mm film--the standard format for cinema--contains an image as well as a visual representation of the soundtrack for that film (see Figure 7.1). The soundtrack which would be read by a special device and translated into sound, much like the phonograph would read the grooves of a vinyl record and used that information to produce sound. This soundtrack used to be analog although sometimes an optical film track (Figure 7.2) is used.
From a viewer's perspective, digital video and digital animation both are experienced as moving images. However, video is generally recorded whereas animations are generated. In producing videos, you use a camera to "capture" events that unfold in time. Usually, these events occur in the everyday, physical world, in which case fidelity becomes a consideration. For example, we would want that our footage faithfully records colors and lighting conditions. In this regard, video is similar to film.
The boundaries between contemporary TV, film, video, and animation are hard to define: This is because video can be viewed on different display devices and stored using different media substrates. Media are not always distributed in the same substrate they were recorded in. A video can be shared over Internet, saved onto a portable drive, recorded onto a DVD, or even transferred back into an analog format like VHS. Video can be viewed on computer monitors, television sets, and cinema screens. Film can be transferred to video, video and computer animations can be printed on film stock, films and video are broadcast on TV, TV and videos can be streamed online, and so forth. It helps to remember that even if video is recorded using one substrate (such as digital magnetic tape, or analog cellulose-based film), it can be edited on machine that uses magnetic disks, and then distributed as a DVD, a Blu-ray DVD, a VCD, or as digital file on your computer.
Watch this short video by YouTube user FlikliTV introducing some of the measurements that determines properties of a digital video. Then answer the following questions for yourself.
What measurement determines whether a video is SD (standard definition), HD (high definition), or full HD?
frame size
height
bitrate
bit depth
What does encoding do?
Processes the original format of a video to one that can be played on devices
Transform analog image signals to digital information (bits)
Transform digital information into analog image displayed on a screen
Reduce the size of a video file and simplifies the image
Embeds proprietary information so that only software with the appropriate license can play the video
What is bitrate not?
The amount of pixel information in each frame of video
Determines the quality of the moving image that is displayed
Is determined by the number of frames per second, the frame size, and the encoding
None of the above
In the early days of digital video, Real Media was a popular format for streaming video. Streaming is a way of viewing video that allows you watch a video without downloading the entire file. Instead, your computer downloads parts of the video as they are needed. You can save a lot of time that way. The Real Media video format is now largely obsolete, and newer formats for streamed video are more commonplace. Nowadays, most people who own a smartphone often will watch streaming video.
Compression is very important in video, as you have already seen, but detailed discussion of video compression can become extremely technical. Basith & Done (1996) give a useful introduction to video compression. The important thing to note is that compression can produce unwanted artifacts and can slow down the production process, and that there are commonly used compression standards, such as MPEG-1, MPEG-2, and MPEG-4. If you want to learn advanced concepts on video compression, see Rui del-Negro (n.d.). Although these articles are somewhat older, the basic issues described remain current. What has changed are standards and available technologies for video. High-definition (HD) and other newer formats (such as 4K) are now available both on Web video platforms (such as YouTube and Vimeo) and for broadcast TV.
Allot 15 minutes
For this activity, watch this video by YouTube user Techquickie about interlaced vs. progressive scan video.
When you read that a video's format is 720p or 1080i, what do the "p" and "i" stand for?
Assume that you're watching a video on an older display device (such as non-digital television) that displays interlaced video.
At first, the screen is blank. Here, the blank screen is represented as this purple rectangle.
The next image that is supposed to be displayed is a solid block of blue.
Now pretend that you had the ability to slow time down, so that you can see the TV updating every line on screen. (And pretend that the scan lines are very thick, and that there are only a few of them.) Which sequence of images below most closely resembles the sequence of events that you should expect to see?
Sequence 1
Sequence 2
Sequence 3
Sequence 4
Basith, Shanawaz A. (1996, May 24). Digital Video : An Introduction. Retrieved January 30, 2010, from http://www.doc.ic.ac.uk/~nd/surprise_96/journal/vol1/sab/article1.html
Basith, Shawanaz A., & Done, S. R. (1996, June 14). Digital Video, MPEG and Associated Artifacts. Retrieved February 2, 2017, from https://web.archive.org/web/20170722211340/http://www.doc.ic.ac.uk/~nd/surprise_96/journal/vol4/sab/report.html
FlikliTV. (2015). The Very Basics of Digital Video. Retrieved from https://www.youtube.com/watch?v=-1s-SuUQYs4&feature=youtu.be
Rui del-Negro. (n.d.). DVD-HQ : Data compression basics : Video compression. Retrieved January 19, 2019, from http://dvd-hq.info/data_compression_3.php
Techquickie. (2016). Interlaced vs. Progressive Scan - 1080i vs. 1080p. Retrieved from https://www.youtube.com/watch?v=H_o5h5SK_70