Clip: source material for a movie. A clip can be a movie, a still image or an audio file.
Frame: basic unit of time
NTSC (TV): 30 frames per second (f.p.s.) (29.97 for colour television);
motion picture: 24 f.p.s.
Digitisation : Capturing information from a video source for use on the computer
The Society of Motion Picture and Television Engineers (SMPTE) standard
Describes any frame of video in terms of: Hours:Minutes:Seconds:Frames
So 01:07:34:16 would be: 1 hour, 7 minutes, 34 seconds and 16 frames
Different for platforms:
QuickTime (MOV) - native to Mac
Audio-Video Interleave (AVI) - native to Windows
Similar in use and appearance
Quicktime has become more flexible and modern (compression, streaming)
Special players required to play on opposite platforms
Compression: method by which data is restructured or removed to decrease the size of files.
Decompression: method by which data is restructured after compression to allow use of the files.
CODEC: Compression/Decompression system
Video files are typically large
Internet is (mostly) a low-bandwidth environment
Large amounts of data contained in a video difficult to transmit on the Internet
Therefore, compression necessary to move the data effectively
loses no data but...
small size reduction, max 3:1
loses information but...
much greater compression
JPEG: for stills
Motion JPEG: a series of still JPEGs
released in November, 1991
used with CD-ROMs
frame size of 360 x 240 pixels. It has a VHS-like quality.
Compression Formats (cont.)
application of MPEG-1 to full-size video
"pixel-vision" or "chiclet-vision"
released November, 1994
full-motion broadcast video version of MPEG, used by DVD-Video.
MPEG-3: never released by the Group.
MPEG-4: the HDTV standard
Motion Picture Experts Group (MPEG)
highly compressed, used on computers and for broadcast applications, MPG extension
uses a lossy CODEC
The MPEG CODEC uses this method: instead of saying “A VERY DETAILED FRAME OF VIDEO” “A VERY DETAILED FRAME OF VIDEO” “A VERY DETAILED FRAME OF VIDEO” “A VERY DETAILED FRAME OF VIDEO” etc. It says: “A VERY DETAILED FRAME OF VIDEO” - KEYFRAME <identical frame> <almost identical frame> “A VERY DETAILED FRAME OF VIDEO” - KEYFRAME <identical frame> etc.
30 frames per second
Audio - CD-quality with full 44 kHz, 16 bit, Stereo
Data rate - 140-170 kilobytes/sec or approximately 10 MB per minute
Internet Video Basics
Video files on the web are either
linked from a page
embedded in the page
Download time depends on
general Internet traffic
For “raw” video, every user has a copy of the video on their system
Most common video formats can be played back on a standard system with correct hardware
Some older systems require special hardware for MPEG playback
Surf Time! Quicktime and other “raw” video types
Incorporating Video Files In Web Pages
Standard Link tag: <A HREF="myvideo.avi"> A video clip</A>