Analog
Video was originated using an analog signal - a continuous voltage
varying in time and values. It represents video as a wave form.
A problem with an analog signal is that it degrades during processing
through the signal chain. In other words everytime you copy it, it loses
quality. Each copy is called a generation.
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2nd generation
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3rd generation
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Digital
A digital signal is a series of numbers each representing the analog signal
voltage at a specific moment in time. In other words it measures the analog
signal and translates it into numbers.
An advantage of digital is that when it is copied, the same
numbers appear on the copy. It is not a dub, it is a clone. As the copy
is indistinguishable from the original there is no generation loss.
Editing in digital software such as IMovie, Premiere
or FinalCut Pro is described as nonlinear because your sources are not constrained
to a linear medium, such as videotape.
With videotape you need to fast forward or rewind in a linear fashion to
get to your point of interest. With a nonlinear program,
you can access any source clip instantly, without shuttling tape, and you
can change the sequence of clips in the program without rerecording.
Digital software such as IMovie, Premiere or FinalCut
Pro edit by creating a detailed set of instructions called "projects".
A project lists all the clips that you intend to use in your edited video
program. It contains all your editing decisions, including the arrangement
of clips, transitions, audio levels, and effects.
A project does not contain the video
files themselves---only pointers to those files, called clips.
As a result, you never alter the source files directly.
So it is called nondestructive editing.
Because it is simply a detailed set of instructions,
a project is a small file, often less than 1 MB.
Metaphor:
Compare a "project" with a "musical
score". Just as sheet music refers to instruments and indicates when
they should play, the project refers to media files and when they should
play.
You can slip sheet music into your pocket, but
the actual orchestra is considerably more bulky!
The video track on a piece of videotape consists of a series of still images,
or frames, that , when played in sequence, appear to be moving.
When motion picture film was
invented, it ran at a frame rate of 18 frames per second (fps). With
the advent of sound, the frame rate had to be increased to 24 frames per second
to get audio that sounded right.
The frame rates of video vary, depending on where you live (see Video Standards
below). The frame rate for full motion video in North America is approx. 30
fps. The actual exact frame rate for digital video in North America is 29.97
fps. This is based on adapting the USA's 60 Hz system to color television.
(I know...huh??)
To compress our files down for the internet we can adjust our frame rate.
Many internet movies that we see are around 10 to 15 fps. For more information
about these different compressions go to http://docs.info.apple.com/article.html?artnum=60766
The process of digitally editing video requires a HUGE amount of information
to be squeezed through some little wires and tiny circuits. If things aren't
configured correctly, or if your computer is not powerful enough to handle
the load, or if you have other programs open at the same time, or if you have
not optimized your computer recently, and on, and on.......you will occasionally
get dropped frames!
Dropped frames happen when you are either importing or capturing video....or
when you are rendering or outputting video. A dropped frame is exactly that....
a frame that has been dropped or skipped over. If it is only one or two frames,
you probably can't tell the difference in your video. Anything more than that
and it will either make your video look jumpy, or it will just not allow you
to continue to capture or render.
For a variety of reasons, different types of video were developed in different
parts of the world. These standards were designed to regulate the quality
of video that broadcast to television sets around the world. Different video
standards have different frame rates, color characteristics, and quality levels,
among other things.
At present, there are three major analog broadcast standards, and all of
them will be superceded by digital broadcast standards in the coming years.
NTSC - This is the analog broadcast standard in North America and
Japan and has a frame rate of 29.97 fps.
PAL - This is the analog broadcast standard in most of Europe and
Asia and has a frame rate of 25 fps.
SECAM - The rest of the world, which includes Africa, the Middle
East, etc. uses this standard which also has a frame rate of 25 fps.
DTV - In 2006, the United States will adopt this new digital
television standard. Already many TV stations are broadcasting DTV signals.
It has been rounded off to a frame rate of 30 fps.
For more information about video standards, go to http://www.tvradioworld.com/directory/Television_Standards/page2.asp
Assemble/Insert Editing Only
A typical analog editing system a few years ago consisted of two video
decks and a controller. One was called the "Source" deck, the
other was called the "Master" deck.
This worked fine for straight cuts or Assemble edits (edits that
were assembled one after another), and for Insert edits (edits that
were later inserted over top of assemble edits)
Assemble Edit
Inserting Edit
Inserted Edit
A/B Roll
A more ideal analog system would enable transitions between video clips.
This was accomplished by having two video decks (A and B) which could then
edit to the Master deck.
As the two tapes (A & B) played, a video switcher/controller
could mix the signal from tape A with tape B to record on the master tape.
This way, you could create dissolves, wipes, and other effects.
Note- If two scenes were on the same source tape, it had to
be copied onto the B roll before dissolves and other transitions could be
performed.
Analog Full Editing Suite
In order to create professional broadcast video you need to
add the following:
A TBC (Time Base Corrector) which lays down
time code onto the Master tape (Exactly what a digital camera does internally
now).
A CG (Character Generator) which generates titles and
text that is laid down on the Master tape.
A DVE (Digital Video Effects Generator) which processes
a portion of the video signal digitally to create special effects. This
is also transferred to the Master tape.
All of this equipment is incredibly expensive. Added to the
expense is the need for broadcast quality analog cameras (Usually Betamax)
which are thousands of dollars.
You can now do everything you see here
with a 3 chip digital camera, high powered PC, and digital editing software.....for
a mere fraction of the cost. This digital video revolution has democratized
video production!!!!
Time Code
Timecode enables every recorded frame of video to be numbered. It numbers
every frame, second, minute and hour.
Why is timecode so important?
If you've scrolled through your home VHS deck you may have noticed a
counter which advances as the tape advances. The problem with that counter
is that once you turn the power off then back on, it resets itself to
zero, no matter that you may be 40 minutes advanced into your tape.
With timecode imbeded into a tape, if you're 40 minutes into the tape,
the counter will read 40 minutes, no matter if you turn the deck on and
off or even put the tape into a different deck. Not only does this make
it easier for you to find stuff on your tapes, it also makes it possible
for the video deck to access any individual frame on the tape automaticall,
thanks to device control commands sent from your computer. When you log
in your tapes, this is invaluable.
Logging
The most tedious (and therefore, the most neglected) part of editing involves
watching your source tapes and noting the selects--the shots you
want to use in the program. Using your softwares capture window and device
control can make the logging process close to painless. If your tape has
timecode, your log can serve as a batch list, which is a list of
timecode start and end numbers that can be used to automate the capture
process.
Capture
If you are using a digital camera connected to your computer through firewire,
capturing video is a piece of cake. Your digital camera already compressed
the video and converted it to digital format. All you have to do is have
a fast connection (firewire) to your computer and a big enough harddrive
to store the file.
If you have an analog source, you need a capture device which can digitize
the video. Up until recently you had to buy a capture card for your computer
(which almost always gives you trouble). Now it is easier to just dub your
analog video to your digital video camera, buy a firewire card for your
computer and transfer the digitial video to your harddrive.
Scratch Disk
Before you capture video, be sure you know where the captured files are
going to be stored!!!! They are stored to your "Scratch Disk".
This is just the location that you designate for captured movie clips.
Go into your Preferences file in your editing software and set your Primary
Scratch Disk to be on your fastest disk. (The fastest disk will be more
capable of capturing all the frames successfully.) You will have choices
on where to save it. I recommend that you create a folder on your
fastest drive and have it store the files there.
Batch Capture
This just means that you capture your video in bunches...or batches!
You do this through your device control that is built into software such
as Premiere and FinalCut Pro. This allows you to choose the edits you
want captured, push a button, and have the computer capture everything
while you go out for a coffee break :)>
EDL (Edit Decision List)
An edit decision list , just takes the information from the batch capture
and exports it out to a list that can be used by other systems to recreate
the project. For instance, if you created a project originally in Premiere,
you can import the editing decision list into FinalCut Pro and recreate
the project.
Saving Projects
Because your project file embodies all your editing decisions, protecting
it from possible mishaps is crucial. As with any important file, you
should save your project often and keep backups.
Since the project file is small you can always save it to a floppy or zip
disk. Keep your original footage and project file on the schools hard
drive but make sure to take a copy of the Project and EDL with you.
Locating Missing Files
As you've learned, projects are simply a set of instructions that refer
to files on a drive. When you open a project, the software looks for the
files to which the project refers. If the source files have been moved,
deleted, or renamed since the project was last saved, your editing software
may have trouble looking for them. It will prompt you to look for those
'missing' clips. Once you find them it will prompt you to confirm your choice.
All you need to do next is resave your project.
If your source files have been deleted, you will need to recapture them.
You can use your EDL to do this.
