Digital Video An Introduction to the Digital Signal File Formats Acquisition IEEE 1394

Objectives  Identify common file formats  Discuss the components of the digital video signal  Discuss acquisition strategies  Investigate spec’s for MiniDV and IEEE 1394

Digital Video Is...  Does not include video devices controlled by a computer such as a level 3 laserdisc.  Any video that plays on a computer as a digital signal.

Hardware Suggestions  High speed Pentium  Pentium II with 500MHz will work  Bigger and faster is better!  Lots of RAM  128 should work  512 meg or more really improves performance!

Hardware Suggestions  Hard Drive – Large & Fast  Average MiniDV rate is 3.5 megs/second!  Firewire card  Sound card  Fast bus architecture

Software Suggestions  Modern Operating System!  Win 98 has a file size limit  Win 2000 or XP better for PC  Non-Linear Editing Software  Graphics Software  Special Effects Software  Authoring Software  Other Utilities as needed

Video File Formats  AVI  A udio V ideo I nterleaved  Microsoft's native format

Video File Formats  AVI  File format, standard, etc.  Debuted in 1992  A response to Apple's QuickTime format  Both an application package and a system architecture

Video File Formats  MOV  "QuickTime"  Apple's native format

Video File Formats  MOV  Also available in a Windows compatible format  Multiple versions of QuickTime floating around!!  I'm not sure what the most current version is (5.0)

.AVI &.MOV  Both formats are standards and relatively stable. CODEC  All formats are dependent on what CODEC was used for compression.

Video File Formats  MPG  Motion Picture Experts Group  High expectation -- low result!

Video File Formats  MPG  Uses hardware compression  Compression technique is "lossy“  MPEG-2 is a common DVD format

Video File Formats  FLI  "FLIC" format used by AutoDesk Animator  DVI  D igital V ideo I nteractive  Format comes and goes  Some CD use

Prediction....  Traditional formats based in the analog world will eventually disappear as new digital domain formats emerge as standard. Good-bye AVI & MOV Hello MPG!

File Size Common Variables  Display (Picture) Size  Video Rate (# of frames)  Audio Rate  Color Model (Depth)  Compression

Compression Defined The process of removing or restructuring data to decrease file size.

Display Size 640 X 480 Full Screen 320 X X X 120

Display Size DV default screen size is 720 X 480 Display size determines overall number of pixels. 720 x ,600 pixels

Video Rate Number of captured video frames determines overall file size. More Frames Larger Files

Aspect Ratio NTSC 4 units 3 units 16 units 9 units DIGITAL STANDARD

Audio Capture Rate More Audio Data Larger Video Files

Color Model 320 X 240 Pixel depth (color planes) also determines overall files size. YUV9 - 9 bit color RGB bit color

Compression Ideal Ideally, compression must achieve a balance between controlling data rate and maintaining picture quality.

Camera Compression for DV DV camera CODECs apply approximately a 5:1 ratio of compression to control file size.

Video Capture Rate Capture Rate Smooth Playback File Size Balance For Optimum

Acquiring Video Files

Possibilities!  Capture from analog camera or tape sources  Transfer from digital sources (i.e. “Firewire”)  Video clip collections  Other output from software packages  Animators,  screen captures,  etc.

Acquisition Schemes Analog “Tape” Video to Capture Card Audio to Sound Card Digitize by Card Set screen size Set # of frames Set file format Set compression Set audio parameters Storage Analog “Capture”

Transfer Protocol for DV Digital Device “Firewire” IEEE 1394 Transfer Card Video File To Disk

Acquisition Schemes Digital “Tape” Firewire to Card Source provides Digital signals Card only transfers Storage Digital “Transfer”

Acquisition Schemes Various “Levels” Of Firewire Cards Storage Digital “Transfer” Firewire to Card Apply various formats Some mild compression Software attributes

Card Costs AnalogDigital $200 & Higher$75 and Higher

DV Format Advantages  High Quality Video & Sound  No “generation” loss from analog/magnetic medium combination  No capture card settings  International Standards Approach

Typical Digital Formats TapeVideoQualityClass MiniDV Digital 4:1:1 HighConsumer, Prosumer Digital-8 Digital 4:1:1 HighProsumer, Industrial DV Digital 4:2:2 HighProfessional

MiniDV & Digital 8 Misc. Spec’s  /- lines of resolution  720 X 480 frame size  frame rate  Audio  4 channels of kHz  2 channels of or 48 kHz

IEEE 1394  International Standard  Transfer Device Only  Usually some associated software  Cable and card handle two-way transfer  Picture and sound  Device Control  Time Code

IEEE 1394  Serial Device  Transfer Rates up to 400 million bits/  Will be even faster in the future!  “Firewire” by Apple  4 to 6 connector  “I-Link” by Sony  4 to 4 connector

Quality Frame Rate & Resolution Bigger Files More Bandwidth Higher Quality Image Less Data, Faster Renders Tradeoff

Analog to Digital An analog to digital (and digital to analog) conversion can often time be made via wires!

Wrap Up  Knowing the specifications for both audio and video formats are important as you produce and distribute final media products.  Digital video is an excellent media for creating and editing but also will monopolize hard drive space!

content & curriculum created by Dr. Mark Mortensen University of North Texas Copyright C. Mark Mortensen 2002