Codec, What’s a Codec? A Technophobes Guide to

Digital VideoJoann Flick

Agency for Instructional Technology

A Very Brief Overview of Digital Video

Transmission Technologies

What the heck…Why you need to know…How to use this information and explain it to others…

KbpsMbpsModemCodecMPEGISDNDSLLAN WANT-1POTS

POTS = Plain Old Telephone Service

AKA dial-up connectionWhat most people use from home to access the Internet (really)Size: soda straw 28-56 Kbps

ISDN/DSLISDN: Integrated Systems Digital Network (64 Kbps)DSL Digital Subscriber Line (512 Kbps)Both use regular phone lines to bring higher-speed connectivitySize: garden hose (at least 3 times to 10 times as big as the soda straw)

T-1A long-distance, point-to-point, dedicated line that usually connects a computer network to the Internet1.544 MbpsSize: a drainage pipe (3-10 times the size of the garden hose)

LAN/WAN = EthernetUsing copper wire(twisted pair) or coaxial cable, the most popular way of networking a bunch of computers within a building or campusFast, broad pipeline: 10-100 MbpsSize: a drainage culvert (6-60 times the size of the T-1 line)

Wireless LANEverything a LAN/WAN is, except the wiresUses transmitters and receivers to move data around a network802.11

Cable BroadbandUsing a digital device, access to the Internet across existing cable TV service lines Hefty bandwidth capacity: up to 500 MbpsSize: A big drainage culvert (twice to 5 times the size of Ethernet)

DatacastingUses a digital TV signal to send data to a receiving device connected to a computerIt’s a DOWNSTREAM delivery systemLots of capacity (10-15 MBPS)Size: drainage Culvert

Codec

Video CodecCodec: Compression-Decompression or Coder-Decoder…a program for compressing all the millions of pixels in a video file so that it can be transmitted, decoded, and viewed. Not every single pixel of every single frame is transmitted, the Codec uses a kind of short hand to transmit enough info to construct the moving image.

Types of CodecsMPEG (1, 2, 4, 7…and more…)QuicktimeMP3 (for audio)

Codecs: how do they look?

48k

Codecs: How do they look?

1.5M

48K

1.5 M

Why?

Why?

Less information transmitted = less bandwidth consumed