DIGITAL FOUNDATIONS
Kurt Ralske
BASIC VIDEO DEFINITIONS
pixel: the smallest unit of a digital image.
Pixels have 4 components (ARGB -­‐-­‐ alpha, red, green, blue). Usually, each component is represented with 1 byte: a number in the range 0 to 255.
resolu;on: the number of pixels in each frame of video.
It’s expressed as WIDTH Qmes HEIGHT.
Some standard resoluQons -­‐-­‐ PLEASE MEMORIZE THESE:
720 x 480 (SD NTSC = standard definiQon)
720 x 576 (SD PAL = standard definiQon)
1280 x 720 (720 HD = high definiQon)
1920 x 1080 (1080 HD = high definiQon)
aspect ra;o: the raQo of width to height.
Common aspect raQos are 16:9 (HD) and 4:3 (SD).
What is the difference between resoluQon and aspect raQo?
Aspect raQo tells you nothing about the resoluQon of the video -­‐-­‐ for example, a 16:9 video could be 1920 x 1080, 32 x 18, 16000 x 9000...
Changing aspect raQos usually involves some compromise, as shown here:
frame rate: how many frames per second.
Common frame rates are: 29.97 (NTSC), 30, 25 (PAL), 24, 23.976 (DVDs)
However, you can make your frame rate any speed you like.
interlaced: only half of the image is recorded at once. The odd-­‐numbered horizontal lines are recorded on the first pass, then the even-­‐numbered lines are recorded on the second pass. Recording is done at double the frame rate: half as much, twice as oeen.
progressive: the enQre frame is recorded at once.
Video formats are oeen described by height + “i” or “p” for interlaced or progressive: 480i, 720p, 1080i, 1080p
video compression: throwing away informaQon from your video file, so it can play easier on your intended delivery medium. It is a necessary evil. (More on this next week.)
compression format: a way of represenQng a video using less data.
Common compression formats: H264, MPEG-­‐2, AnimaQon, Apple ProRes, Photo-­‐JPEG
codec: COmpressor / DECompressor. A soeware program for compressing and uncompressing video. The compressor translates the video into a compressed file. The decompressor knows how to read the compressed file and turn it back into all the pixels. media architecture: a collecQon of codecs. Examples: QuickTime, AVI, RealMedia
NOTE: QuickTime is not a compression type!
THE ARCHITECTURE OF QUICKTIME
Tracks
All QuickTime files have one or more tracks. A track can contain:
Movie data / Sound data / SQll image / Timecode / Text (subQtles, capQons)
MIDI data / QTVR data A QuickQme file can contain many different types of data, or many tracks of the same type (for example, 4 different sound tracks simultaneously is fine).
References
A reference is a pointer to where some informaQon (usually video or audio data) is stored. A reference is a like an alias. It’s used instead of copying the data. If you copy a 4 gigabyte file, it takes forever and uses up 4 gigs on your hard drive. But if you save a reference, it is fast and Qny.
If you “Save As” a copied file, you can choose to save it as either a reference or a “real copy”.
A QuickQme file can contain both references and “real data” in it. It could also contain only a reference.
References can be helpful someQmes, but be careful: if the data the reference points to is moved or lost, the file containing the reference will no longer play
QUICKTIME PRO
The “Pro” version of QuickTime 7 (now obsolete) is the only video ediQng applicaQon that allows you to make modificaQons directly on a video file! This is incredibly useful.
If you want to use QT Pro at home -­‐-­‐
To DOWNLOAD QUICKTIME PLAYER 7:
hnp://support.apple.com/kb/DL923
...then upgrade to to “Pro” version by purchasing a registraQon code for $30 from here:
hnp://store.apple.com/us/product/D3380Z/A/quickQme-­‐7-­‐pro-­‐for-­‐mac-­‐os-­‐x. Once you have the code, open QT 7 and go to the menu item “QuickTime 7 > RegistraQon”, and enter your code
QT Pro Presenta;on SeMngs
Inspector window ( + I)
Displays useful informaQon about the QuickTime file Proper;es window ( + J)
Set playback properQes for an individual track of the file, or for the enQre file Tip #1: to make a file automaQcally present at fullscreen size, select enQre file in the ProperQes window, then click the checkboxes “AutomaQcally play movie when opened” and “Enter fullscreen mode when opened”. (Don’t forget to save now.)
(...unfortunately this trick works only if you play back the file with QT 7...)
Tip #2: you can change the size, aspect raQo, or horizontal/verQcal orientaQon of your video
(Again, don’t forget to save aeer changing your serngs.)
 + K A/V Controls -­‐-­‐ modify the playback of audio and video.
(need to re-­‐save the movie or these serngs to hold)
Catalog of QuickTime Pro Playback seMngs: Think about how you could abuse these for crea<ve purposes.
Menu seMngs:
>> "Edit" menu: Add to Movie Add to SelecQon & Scale -­‐K seMngs: Brightness Color Contrast Tint
Playback Speed
Audio Pitch Shie
>> "View" menu:
Loop
Loop back and forth
-­‐J seMngs:
Enable / disable tracks
Scale (with or without changing aspect raQo)
Flip or rotate
QuickTime Pro: EdiQng shortcuts
(1) MAKE SELECTION
(2) COPY (
-­‐ C) (3) PASTE (
-­‐ V)
__(1)__ MAKE SELECTION Place playhead at a spot you like, then press frame.
-­‐ B. This selects the current Expand the selecQon by pressing SHIFT + arrow key (single frame) or SHIFT + spacebar (play to select).
__(2)__ COPY Press -­‐ C. The selecQon you made is copied into the clipboard (the clipboard is an invisible storage place),
__(3)__ PASTE Press -­‐ V. The selecQon you made is copied from the clipboard to wherever the playhead is currently located.
If you want to copy into a new QuickTime file, press new QT player, then -­‐N to create a -­‐V. (If you want to have the selecQon repeat, paste it several Qmes.)
[ the same info as the previous page, a second <me...]
QT Edi;ng, step-­‐by-­‐step
#1. Set playhead to start point Use “home” and “end” keys to play through the file. Park the playhead on the beginning frame of the selecQon you want to make. Then press “ + B”. (Note the two triangles that define the selecQon area.)
#2. Set selec;on end point Hold down the “shie” key and press the “end” key to increase the size of the selected area. (Tap the “end” key once to advance one frame at a Qme, or hold it down to play at normal speed.)
#3. Copy selec;on to clipboard If you’re happy with your selecQon, press “ + C”.
#4. Paste selec;on Press “ + V” to paste your selecQon where you want it to go. If you paste right aeer copying, the copied selecQon is put at the endpoint of the selecQon. You may want to paste into a new QT file (“ + N”), or you may want to move the playhead to set a new insert point in the current file.
HW Assignment: Due Oct 23
1) Go to hnp://trailers.apple.com/trailers/ and download any 3 trailers you like.
Be sure to download movies in 720p format.
Once downloaded, make sure you save files to disk.
2) Recompress the files. Here’s how:
Open file in QT 7.
Go to “File > Export”.
Set “Export” to “Movie to QuickTime Movie”, then press “OpQons” bunon.
In “Movie Serngs”, press “Serngs”
set Compression Type to “Photo-­‐JPEG”
3) Make an experimental video piece by aggressively ediQng the files using QuickTime Pro and the techniques we explored in class.
Try starQng with a small amount of source material. Repeat and vary to extend something small and insignificant into something big and meaningful.
Some techniques you can explore are looping, replacing soundtracks, "Add to SelecQon and Scale" to change speed, varying color, etc.