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Basic Digital
Video
C.J.C, 05-01-1998
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- Shooting video for Digitizing - Digitizing for use with Director - Digitizing for use on the Web - File Sizes (table of different sizes) - Resources (shareware digitizers, codec info, DV magazine)
- Examples!
Web/CD-ROM |
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05-01-1998Digial Video is hard to do and it takes a lot of time. Computers struggle with digital video, even today, because it represents the media with the most information in it. Digial video is a combination of sound and many still pictures a second. This will get easier as the technology catches up with desire, but at the time of this writing, digital video is still time consuming and stuck in small windows with bad quality.
That being said, it's also really fun! And no other media is so captivating then moving pictures and sound, at least not yet...
Digital Video is different then regular tape video in three main ways.
1 Digital video does not loose quality when you make a copy. This is big. Regular video, like a photocopy, looses quality each time you make a copy. Digital video, like text in a word processor, makes exact copies every time.
2. The picture above is of the construction window of the video editor, Adobe Premiere, a popular application for editing video for CD and the Web.
Digital video can be cut and past like text. This means "nonlinear" editing is possible. In other words, you can edit video as easy as you edit text in a word processor, literally "cutting and "pasting" it at will.
3. Digital video is unwieldy. Because video is made up of many sound and pictures, digital video puts a strain on today's computers. Each frame of video is a single picture, if you have 30 frames a second, and then add sound, you can see how big a 2 hour movie would get!
No matter how much information you may read here, the bottom like with digital video at this time is that you must experiment and test your files and projects over and over again.
Basic Concept of Digitzing Video:
Video on a VHS tape is analog. To make it digital you need a VCR to play your VHS tape, a computer that can accept a video signal, and software to let you record and edit that signal onto the computer's hard drive.
This is what digitizing software looks like while you're digitizing. Notice the "Rec" and "Stop" buttons like a VCR, and the small window size of 240 by 180
The higher end computers coming out at the time of this writing are often video ready. Once you get digitizing software like Fusion 1.1, editing software like Premiere, and a VCR, you're good to go for making small movies for CD and the Web.
For digitizing and editing video for playback on a VCR or for broadcast on TV, you currently need a very large and fast hard drive, and digitizing and editing hardware like Media 100 or Avid, all hooked up to a professional VCRs and one, or even two, fast computers.
There are a few key concepts to all digital video that affect it's size and quality.
- Frame Rate: TV is broadcast at 30 frames per second (fps), most CD video is 15fps. Why 15fps?, because that is the lowest speed you can use before the movie starts to look real jerky and more like a slide show then a movie. And because the less fps you have the smaller the movie is.
- Color: Most movies use millions of colors now, but if you can use 256, you'll save space as more colors mean bigger files.
- Compression: "Codecs", which stands for "compression/decompression" are little pieces of software designed by a company that compresses video. Compressing video involves the black art of taking away information in each frame without changing the quality too much. This is done by taking out repeating colors, cloning repeating information, reducing the audio information, and other voo doo that programmers do. Cinipak, JPEG, and MPEG, are some of the most common Codecs.
- Data Rate: The rate at which the video is played at. For a 4X CD 200K/second is good. For the web over a fast Internet connection, 35k/second. The lower the data rate, the lower the quality.
- Frame Size: In the beginning of digital video the tiny "postage stamp" sized 160 pixel by 120 pixel window were the big thing. Not only where they small, but they were terrible resolution. Nowadays we're seeing 240 by 180 size windows on the Web and even bigger windows on CDs.
Frames size directly relates to file size because a bigger frame means a bigger picture for each frame of the movie.
A 160 pixel, by 120 pixel frame size with a "controller" at the bottom to control playback.
Shooting Video for the computer:
Shooting video for a CD or the Web is different then shooting video for the TV. TV's have much bigger screens and play at 30 frames a second. If you know you're going to the small windows of CD and Web video (at the time of this writing anyway) here are some tips for shooting.Imagine that the finished product is not much bigger then the viewfinder of the camera.
-Stay close
-Use simple backgrounds
-Do few wide shots
- Limited dialog
The key to Web video at the time of this writing is to make it small and short. Technically, the key is to "Flatten" the movie so it can be played over the Web by Web servers to both Mac and PC platforms. (Sometimes "flattening" is just a setting that says "make playable on mac and PC?")At the time of this writing, two big technology advances were happening. QuickTime 3.0 had just come out. QuickTime 3.0 has been reported to be very impressive, but was not used here (see Resources). It claims to do streaming and multiple data rates.
A new Codec called the Sorenson Codec has just come out.
Media Cleaner Pro 3.0 is on the way and being written up as amazing.
But, given the existing technology that I had access to: There are two main ways to get video to the Web after you have digitized it and edited it:
1. Quicktime movies that download to the person's computer, or start to download, and then strart to play once there is enought of the movie on your harddrive. Quicktime currently allows for better quality, although delayed, movies.
2. Streaming Video. RealVideo, and other companies like VDOLive, have been perfecting streaming audio and video for years and has achieved impressive results even over 28.8 modems. This allows for broadcast of live shows, but also requires servers that are running the software and generally limites the quality due to lack of bandwidth. Producing for RealVideo information is in the Resources section.
Once you have your video in digital form you have to use a Codec (fancy name for a compression technique) like "Cinepak" and make sure to "Flatten", or "make playable on multiple platforms".
You must also make sure to name your movie with the ".mov" extension, like this: "movie.mov"
Once this accomplished, you have to put the video into an HMTL document using the "EMBED" tag, so that people can see it using a Web browser.
You have to use a "Mime" tag so the Web browser will know what kind of movie it is. This example tag uses the "video/quicktime", mime so Web browsers will know that this movie is a Quicktime movie.
Here's an example of the HTML, feel free to steal it.
<HTML>
<HEAD>
<META HTTP-EQUIV="content-type" CONTENT="text/html;charset=iso-8859-1">
<META NAME="video example" CONTENT="example of video code">
<TITLE>Take a look at my Video</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<CENTER>
<P>
<EMBED SRC="video_clips/skydive96_sm.mov"
PLUGINSPAGE="http://quicktime.apple.com"
WIDTH="161" HEIGHT="140"
CONTROLLER="TRUE"
LOOP="FALSE"
AUTOPLAY="TRUE"
CACHE="true">
</P>
</CENTER>
</BLOCKQUOTE>
</BODY>
</HTML>Then, like all Web pages, you have to post your HTML document, and the movie, in the EXACT file hierarchy as they were when you built and linked them.
Now you can test your creation with a browser, discover problems as you always will, and fix them and retest, then repeat, and repeat, until you get it right.
Making video for Director/CD-ROM, etc.
Making video for CD is a little easier because you can make bigger files and you don't have to post them to the Net. Generally speaking you can also use bigger frame sizes and rate, such as 200k/data rates and 320 by 240 window sizes. The Cinepak codec is your best bet at this time. Experiementation is the name of the game here. Make one clip, try it in a project on multiple platforms, test again, and again, then once you find what you like, make more clips.Here's a quick and dirty way to get video usabable by Director:
You will need a VHS tape with something
you want to digitize recorded on it. Use Fusion on a video ready Mac hooked up
to a VCR to digitize just the part of the tape that you
want. The Fusion window will look like this on
the computer screen. Set Fusion to the below settings before
you start to digitize.
Under "Record/VideoSettings" choose
"Cinepak" and "Millions of Colors" with "medium" quality.
Make sure "Frames per second" is at 15"
and don't worry about "key frames" or "data rate".
After you have digitized the video, do a
"Save As" and make sure you flatten the movie by selecting
"make movie self contained" and "Playable on non-Apple
computers". Make sure your file has '.mov' extension
and you should be ready to import the file into Director as
linked file. Don't forget to keep the movie in the
same folder as your Director project at all
times.
File SizesFile sizes are changing fast. Compression technology is making it possible to make files smaller and smaller, and quality better. New tools like Media Cleaner Pro, and new versions of QuickTime and Premiere are making it possible to make high quality small files for use on the Net and CD. At the same time, the Internet is increasing bandwidth capability and CD's are getting faster and faster. For these reasons, file size recommendations are difficult. In general a 10 Megabyte movie is still considered very big for the Web and pretty big for a CD.
To give you an idea of where we stand now, below is a chart of some file sizes using Fusion 1.1 and Cinepak Compression.
These file sizes would all be smaller with some work. By using Media Cleaner Pro, or other compression software, you could crunch some of these file sizes in half.
Size of frame
Seconds
Frames Per Second
Cinepak Compression
Colors
Audio
SIZE
160 by 120
10
15
Med
millions
mono
1MB.
160
10
15
Most
millions
mono
1.2MB
160
10
15
Med
millions
mono
1MB
320 by 240
1
30
Med
millions
mono
500k
320 by 240
1
15
Med
millions
mono
250k
240 by 180
10
15
Med
millions
mono
1.6MB
320 by 240
10 second
15
Med
millions
mono
2.3MB
240 by 180
10 second
15
Med
millions
No audio
1.3MB
ResourcesApple's Quicktime Site
http://www.apple.com/quicktime/Quicktime resources (besides apple site)
http://www.bmug.org/quicktime/
http://Blackstone.ca/QuickTimeGazette/latest_news.htmlGreat Basic Codec information
http://www.CodecCentral.comCodec Comparisons
http://www.terran-int.com/CodecCentral/bigpic.htmlSorenson Codec Info
http://www.terran.com/prod/SorensonDev.htmlTerran Interactive, makers of Media Cleaner Pro
http://www.terran.comStreaming video for the web, RealVideo:
http://www.real.comShareware quicktime editing and capture:
for Mac and PC:
http://www.wild.ch/quickeditor/A fantastic resource from Digital Video magazine
http://www.dv.com
