Transcript Fundamentals of Audio Production

Delivery
1
Transporting content
• The method by which audio and video will
be delivered to the consumer will
determine how the content should be
prepared.
• It is important to understand the limitations
and capabilities of the various means of
transporting audio and video.
Copper wire technology
• Telephone circuits using a single pair of
copper wires carried early radio signals
• AM radio bandwidths of 5 KHz
• Vacuum tube amplifiers or “repeaters”
boosted the signals
• “Twisted pair” copper wire still provides
much of the backbone for telephone
transmission
Copper wire technology
• Technological advances now permit
twisted pairs to carry broadband audio
• Twisted pair also carries broadband data
and video signals
• “Coaxial” cable introduced in the late
1930s allowed even greater bandwidth
• Coaxial cable became the standard for
television signal distribution
Copper wire technology
Microwave technology
• Named for the extremely short
wavelengths of Radio Frequencies used
for transmission
• Microwaves travel only in straight lines
• Transmitted and received using tightly
focused parabolic dishes
• Make use of relay stations
Microwave technology
Fundamentals of Audio
Production, Chapter 11
7
Microwave technology
• Capable of travelling great distances – up
to 40 miles
• Capable of extremely large bandwidths
and high data rates
Satellite technology
• Communication satellites orbit 22,300
miles above the equator
• Communication satellites orbit the earth
once every 24 hours
– They are synchronized with the earth’s orbit
– Called “geosynchronous” orbit
• Satellites appear suspended above a point
on earth
– Appear “geostationary”
Satellite technology
• Satellites vary according to power and RF
band they utilize
• Low power lower frequency satellites are
called “C-band”
• High power higher frequency satellites are
called “Ku-band”
• “Transponders” receive signals from earth
stations and re-transmit to earth’s surface
Satellite technology
• Satellite radio services use the S-band
and F-band segments of the spectrum to
transmit multiplexed signals to subscribers
Satellite and Microwave
A transmission system using microwave, satellite, copper and optical fiber
Optical fiber technology
• Optical fiber is made from highly purified
optical glass
• The glass is drawn into a single
continuous strand with the diameter of a
human hair
• Fiber optics use “total internal reflection” to
reduce attenuation
• The glass stand is wrapped in “cladding”
that reflects the light internally
Optical fiber technology
Optical fiber cladding produces “total internal reflection”
Optical fiber technology
EIAJ OPTICAL CONNECTOR
Digital wired technology
• Integrated services digital network or ISDN
developed in the 1980s, offers digital
transmission over the telephone network
• ISDN terminals convert analog to digital,
and vice-versa
• ISDN signals are exchanged between
terminals – not over the Internet
• The bandwidth of ISDN allows CD quality
digital signals to be transmitted in real time
Internet based technology
• Audio and video files can be transferred
over the Internet using the same
telephone network previously described
• Files may transferred two ways
– As complete files – like any other data file
– As a stream – with data transferred
continuously in near-real time
Internet based technology
• Coder-decoder (CODEC) software is used
to compress audio files for Internet
transfer
• Lower compression rates yield better
bandwidth and dynamic range
• 1:1 compression is called “lossless”
compression – preferred by professionals
Internet based technology
• Streaming content is sent continuously
and played immediately as received
• Streaming software includes “buffers”
which store data for a short time before
playback
• Buffering avoids start and stop of the
content stream due to network traffic
Internet based technology
• “Podcasting”
– MP3 files distributed over the web
– Uploaded to and downloaded from servers
– Sent as emails
– “Podcatchers” may use RSS aggregator
software to receive new content automatically
– Still subject to copyright and music licensing
regulation
Broadcast technology
• Audio and video may be transferred long
distances using radio frequency
broadcasting
• The radio frequency signal is modulated
• Modulation superimposes the analog
signal on the radio frequency carrier