2. What is Digital Video?
● Digital video is very similar to film. It is simply a series of
still images.
● The still images are played back quickly enough to
make objects on screen appear to be moving just like
they do in the real world.
● The only difference is that the images are captured on
fields of digital pixels rather than a frame of film.
3. Pixels
● Pixels are tiny rectangles that contain three lights--Red,
Blue, and Green--and can produce about 16.8 million
colors using different intensities of the three.
● They capture light, and save it as a single color.
● Each image is made up of thousands of pixels.
● 1920x1080 is a form of HD, also known as 1080p.
○ This means each frame of video contains 1080
horizontal rows, each containing 1920 pixels.
○ So when you watch HD video, you are seeing
2,073,600 pixels in every frame.
9. Aspect Ratios
● 4:3 → Standard SD, most TVs used to
be this.
● 16:9 → Standard HD, most TVs are
now like this.
● 1.85:1 → Most Theatrical showings
since the 1960s.
● 2.35:1, 2.39:1, 2.40:1, etc. →
Widescreen.
● Everything Else → Weird, rare stuff.
10. 4:3
16:9
CSI: Season 1 (‘00) & Season 15 (‘15)The SImpsons: Season 3 (‘91) & Season 23 (‘12)
11. Down Converting
● When stations receive HD video, they have to convert it
to a format that can be displayed on SD screens
(640x480 and 4:3).
● The most common ways that stations convert are by
letterboxing, cropping, or squeezing.
12. Letterboxing
● Letterboxing is where the
HD video is fit to the
horizontal dimensions of
the 4:3 SD screen. The
problem with this
technique is that you
sacrifice even more
resolution than you have
to by not using all of the
rows of pixels.
14. Cropping (Cont’d)
● Cropping can also be used to “up convert” old 4:3
video in order to make it fit a full 16:9 screen.
● Netflix and FX have both been caught doing this.
● The problem is that you lose part of the picture, and
also lose some of the already inferior quality of the
SD video.
18. Analogy
● Down Converting is like buying a couch, getting home, and realizing it is
too big to fit in your living room. You have three options:
1. Return the couch and buy a love seat (Letterboxing)
2. Saw off six inches of the couch from either end (Cropping)
3. Hit the couch with a sledgehammer until it fits (Squeezing)
● No matter what option you choose, you will not have the same couch you
wanted originally because your living room is too small. With an SD video
feed, you can watch things that were shot in HD, but it will never be the
same as having an HD TV.
20. Title Safe (Cont’d)
● Different types of TVs display different amounts of the
information sent through them from the signal.
● Everything inside the innermost box will definitely be on
viewers’ TVs and is considered “title safe.”
● Everything inside the next box will show up on most
viewers’ HD TVs and is considered ‘action safe.”
● Outside of both boxes is called “overscan,” and
probably won’t show up on most consumer televisions.
21.
22. Frame Rates
● A frame is a single still image.
● The frame rate describes how quickly still images are flashed
on the screen to create a video.
● Frame rates are referred to in frames/second, or fps.
● Our brain can perceive ~10-12 fps as individual images, but
anything faster than that looks like motion.
● Film cameras and projectors both originally required the
operator to hand crank the film through them, so early film
frame rates were often uneven and varied from one showing
to the next.
23. Frame Rates (Cont’d)
● With the addition of
sound, frame rates had to
be standardized to make
sure sounds and actions
always matched.
● 1929 → 24 fps becomes
standard, and still is
today.
25. Digital Frame Rates
● When the US adopted the
NTSC broadcasting standards
in 1941, it was not
technologically feasible to play
video on TV at 24 fps.
● The way films are projected,
each frame is projected twice
to avoid flicker, but the TVs of
the time were not capable of
that.
26. Digital Frame Rates (Cont’d)
● The solution was to create two fields of alternating pixel rows
that -- when combined -- would make up one full frame of digital
video.
● This is called interlaced footage.
● The two different fields are flashed on the screen intermittently
at 60 fields/second. This is because the hum caused by AC
electrical current in the US is 60Hz. The hum could cause
horizontal intermodulation lines otherwise.
● The visible scan lines and motion blur associated with interlaced
footage is called combing.
29. Digital Frame Rates (Cont’d)
● To make digital color video available through the same
broadcasts as black and white, the frame rate for color
video had to be slightly offset so it didn’t interfere with
the black and white sound frequencies.
● The result was that the standard for digital video was
slowed down by 0.1%. This was possible because
timing circuits were developed to regulate the oscillation
of TVs’ electrical current to avoid intermodulation.
● In reality, video we see on TV is being played at 29.97
fps, not 30.
30. Digital Frame Rates (Cont’d)
● The next problem facing TV producers was how to take
movies that were shot on film at 24 fps, and convert
them to video that could be played at 29.97 fps on TV.
● If editors were to simply convert each film frame to a
digital frame, movies would appear to be playing in fast-
motion on TV
29.97 ÷ 24 = 124.9% of original speed.
31. Digital Frame Rates (Cont’d)
● Solution → 3:2 Pulldown
● 3:2 Pulldown takes four full frames, and turns them into
five interlaced frames.
32. Digital Frame Rates (Cont’d)
● TVs today can process information much faster than the
original tube sets, so most display video in progressive
frames.
● This means every frame is singular, and the whole
image is displayed at once.
● When a TV’s resolution is described as “1080p,” it
stands for the resolution as well as the way in which the
TV refreshes images, which is progressive in this case.
33. Digital Frame Rates (Cont’d)
● The new fad is for TV companies to market super high
“refresh rates,” which are the exact same thing as frame
rates.
34. Digital Frame Rates (Cont’d)
● Super high frame rates reduce motion blur, so they can
be valuable for watching sports and playing video
games, but anything over 120Hz doesn't really do
anything.
● Since most cameras don’t record at anything over
60fps, the high-frame rate settings actually play back
more frames than were originally recorded. They do this
by creating new frames in between the recorded frames
that are basically guesses at what the image should
look like. Video
35. Digital Frame Rates (Cont’d)
Some Standard Digital Frame Rates
● 1080i60 → 1080 horizontal rows of pixels, interlaced
footage, “60” fields/second, 29.97 frames/second
● 720p30 → 720 horizontal rows of pixels, progressive
footage, 29.97 frames/second.
36. Codecs
● A Codec is a term used to describe the way in which a
digital video file is compressed.
● It stands for Coder/Decoder.
● After video is captured, it is compressed into a smaller
file that is easier to move around.
● The Codec is the file type that describes the
compressed file.
37.
38. Codecs (Cont’d)
● Lots of other file types also have codecs. .mp3 →
Audio, .jpeg → image, etc.
● The most common video codecs are Cinepak, MPEG-2,
H.264, and VP8.
39. Codecs (Cont’d)
● All codecs are either lossless or lossy.
● Lossless codecs reproduce an exact replica of the
original file. With lossy codecs, some image quality is
lost when the file is compressed.
● There are lossless video codecs (PKZIP, PNG), but all
streaming is only possible with lossy codecs. If lossless
codecs were used for streaming, nobody’s internet
would be able to stream the videos fast enough. To put
in perspective how much data is contained in a film file..
40. Codecs (Cont’d)
● Godzilla (2014)
● It took four special effects
artists six months to fully
animate Godzilla’s scales.
● 762 visual effects crew
members worked on the film.
● With one computer, it would
have taken 445 years to
render the final project.
41. Codecs (Cont’d)
● Shockingly, if you stream Godzilla
online, some detail will be lost
from the film’s original format.
● Your TV, computer, etc. do not
have the audio and video
capabilities to even display the
original movie, let alone
download it fast enough to stream
anyway.
42. Codecs (Cont’d)
● There are two types of compression: Intra-frame and
Inter-frame.
● Intra-frame compression compresses every single
image as an individual still image.
43. Codecs (Cont’d)
● Inter-frame compression looks at adjacent frames to
only store the minimum amount of information to
recreate the original image.
45. Inter-Frame Compression
● The first frame of a new
shot is fully encoded. This
is called the Key Frame.
● For the next frame, only
the changes from the
previous frame are
encoded, saving file
space. These frames are
called Delta Frames.
46. Inter-Frame Compression
● Think of it as if you
were drawing a
cartoon and you
could copy
pictures, erase
parts, and draw
more. Would you
draw a whole new
picture every time?
48. Inter-Frame Compression
● Other popular file
formats like MPEG are
even more lossy,
because they save far
fewer frames than the
original video format.
49. Inter-Frame Compression
● I-Frames are actual frames
from the original footage.
● P-Frames show just what
changes from the I-Frames.
● I-Frames are also called
“Anchor Frames,” and are
used to predict P-Frames
and construct B-Frames from
scratch.
51. Color Correction
● While some examples are more obvious than others,
every major film now goes through some sort of digital
color correction process during post production.
