Audio and VideoAudio and VideoCommunicationCommunication

Transmission of AudioTransmission of Audio

Without wires - Without wires - This is radio.This is radio.Using wires - Using wires - this is what we typically think this is what we typically think of as basic telephone technology.of as basic telephone technology.Cell PhonesCell Phones – Microwaves (E&M waves) and – Microwaves (E&M waves) and Fiberoptic cablesFiberoptic cablesInternetInternet – Satellites, phone lines, Fiberoptics – Satellites, phone lines, Fiberoptics (both wireless and wired)(both wireless and wired)

Cell Phone Frequency Range: 850 and 1900 MHz

Cell phones and Microwave Ovens are Cell phones and Microwave Ovens are close together on the Frequency close together on the Frequency

Spectrum…Spectrum…

Microwave Ovens use 2.45 GHz (GHz = Microwave Ovens use 2.45 GHz (GHz = 101099 cycles per second) cycles per second)

GSM Cell Phones use 850MHz and GSM Cell Phones use 850MHz and 1.9GHz1.9GHz

Why don’t cell phones “cook” you?

How a Microwave WorksHow a Microwave Works Microwaves are absorbed Microwaves are absorbed

by water, fats, and sugars by water, fats, and sugars (the stuff in food)(the stuff in food)

Water is a dipole molecule Water is a dipole molecule with a positive and with a positive and negative sidenegative side

Water molecules constantly Water molecules constantly flip over, trying to align flip over, trying to align themselves with the themselves with the changing electric field of changing electric field of the microwavethe microwave

As the water molecules flip As the water molecules flip over they rub against each over they rub against each other making heatother making heat

http://www.sciencelearn.org.nz

Transformer steps up the voltage to 2000 volts

Magnetron produces the microwave

Waveguide leads wave into oven cavity

Difference between Cell Phone Difference between Cell Phone and Microwave Ovenand Microwave Oven

AmplitudeAmplitude PowerPower

Cell Phone Cell Phone 0.1 Watts0.1 Watts

Microwave Microwave 1000 Watts1000 Watts

ModulationModulation Cell phone is Cell phone is

carrying infocarrying info Microwave is notMicrowave is not

More Information can be More Information can be transmitted if information istransmitted if information is

DigitizedDigitized

Voice and Music are Voice and Music are analog analog datadata

Dots-Dashes, 1’s and 0’s, on-Dots-Dashes, 1’s and 0’s, on-off are examples of off are examples of digital datadigital data

Digital information is coding a signal using Digital information is coding a signal using a binary format, e.g. 0’s and 1’s, dots and a binary format, e.g. 0’s and 1’s, dots and dashes, on and off, Morse Codes, etc.dashes, on and off, Morse Codes, etc.

Analog is the process of converting a Analog is the process of converting a signal into a wide range of continuous signal into a wide range of continuous values.values.

www.bbc.co.uk

http://photo.net/equipment/digital/basics

Photographic picture is an analog image.

Digital picture is made up of many pixels, each pixel is one color.

birminghamstories.co.uk

http://www.nps.gov

Record Vinyl is analog data. The grooves are carved by a needle that was moved by a vibrating needle attached to a diaphragm. The groves are analog as they are a continuous representation of the audio information.

Record Needle - StylusRecord Needle - Stylus Placed in the grooves of the recorded disc and Placed in the grooves of the recorded disc and

transfers its vibrations to a magnet that induces transfers its vibrations to a magnet that induces a current in a nearby coil, creating an electrical a current in a nearby coil, creating an electrical signal that corresponds to the audio. signal that corresponds to the audio.

As the stylus rides along the walls of the moving groove, it vibrates back and forth with each ripple in a wall. Two transducers attached to this stylus sense its motions and produce electric currents that are related to those motions.

Louis A. Bloomfield http://www.answers.com

Transducer:Converts input energy of one form into output energy of another form.

Electromagnets used in Electromagnets used in Tape Players tooTape Players too

A – Tape

HowStuffWorks

The electromagnet consists of an iron core wrapped with wire, as shown in the figure. During recording, the audio signal is sent through the coil of wire to create a magnetic field in the core.

This flux is what magnetizes the oxide on the tape. During playback, the motion of the tape pulls a varying magnetic field across the gap. This creates a varying magnetic field in the core and induces signal in the coil that corresponds to the audio.

Tapes can store analog data (a continuous signal) or can be DAT (Digital Audio Tapes)

Transmission of AudioTransmission of Audio

This is Amplitude Modulation (AM)

http://www.answers.com

Turned into a Electromagnetic Wave

Amplitude is volume and frequency is the pitch.

Audible range:20 Hz - 20 kHz

This is Frequency Modulation (FM).

This requires greater bandwidth but it is easier to cancel out noise.

Turned into a Electromagnetic Wave

Transmission of Analog Data Transmission of Analog Data (Listening to the Radio or talking on the phone )(Listening to the Radio or talking on the phone )

was preferred over Morse was preferred over Morse Codes (dots and dashes) Codes (dots and dashes)

because:because:

Transmitting dots and Transmitting dots and dashes (digital data) dashes (digital data) required a human computer required a human computer to decode the message.to decode the message.

Transmission speed was Transmission speed was slowslow

Voice data can be automatically Voice data can be automatically sent digitally by digitizing the sent digitally by digitizing the

audio and then reassembling the audio and then reassembling the audio later.audio later.

Periodically Periodically take a sample, take a sample, at a rate of at at a rate of at least ½ the least ½ the frequency. frequency. The more The more samples the samples the more more information is information is captured.captured.

/www.webbasedprogramming.com

http://jvsc.jst.go.jp

Digitized Sounds

CD Rom- Digital data CD Rom- Digital data storagestorage

Data is represented as pits and bumps

Track is a outward moving spiral

http://invsee.asu.edu/nmodules

CD Bumps are the digital CD Bumps are the digital datadata

Data Track is typically 3 ½ miles long.

Reading the bumps with a Reading the bumps with a laser and optical sensorlaser and optical sensor

Click for animationhttp://electronics.howstuffworks.com/cd5.htm

The tracking drive keeps the The tracking drive keeps the laser under the track.laser under the track.

The disk motor spins between 500-The disk motor spins between 500-300 rpm as the laser moves outward 300 rpm as the laser moves outward with the track.with the track.

Animation at:http://electronics.howstuffworks.com/cd6.htm

How data is arranged on How data is arranged on CDsCDs

Data is interleaved so scratches on the Data is interleaved so scratches on the CD won’t be a complete loss of dataCD won’t be a complete loss of data

Data is read one revolution at a time, Data is read one revolution at a time, and software orders the interleaved data and software orders the interleaved data in the correct sequence.in the correct sequence.

Extra data is present for error-checkingExtra data is present for error-checking Meta-Data is present to identify songsMeta-Data is present to identify songs

Video CommunicationVideo Communication

Producing Video ImagesProducing Video Images Capturing Video dataCapturing Video data

Transmission via cableTransmission via cable Transmission wirelessTransmission wireless

Storing Video data on VHS Storing Video data on VHS TapeTape

DisplaysDisplays CRTCRT LCDLCD PlasmaPlasma

Digital TV and DVDsDigital TV and DVDs

Brain assembles pixels into Brain assembles pixels into imagesimages

Higher resolution means more dots/pixels for Higher resolution means more dots/pixels for a given areaa given area

Higher Res. Means sharper imageHigher Res. Means sharper image Brain fuses pixelsBrain fuses pixels

How Stuff Works

Brain assembles still images Brain assembles still images into a life-like moving imageinto a life-like moving image

1919thth century novelty items century novelty items Old movies – 16-24 Old movies – 16-24

frames/secframes/sec Theaters – 24 frames/secTheaters – 24 frames/sec TV – 30 frames/secTV – 30 frames/sec

http://www.isntlifeterrible.com

PraxinoscopePraxinoscope

http://brightbytes.com/collection/

TV ‘paints’ image with TV ‘paints’ image with three electron beamsthree electron beams

Hot Cathode emits electrons.

http://www.nickelinstitute.org

Shadow Mask holes are arranged so that each electron beam corresponds to one color and can only excite one phosphor dot

Steering coils around CRT position Steering coils around CRT position the electron beams using the electron beams using

magnetic fieldsmagnetic fields

CRT - Cathode Ray Tube

Electron Beams ‘paint’ the Electron Beams ‘paint’ the screen using a raster scan screen using a raster scan

patternpattern

525 Lines are ‘painted’ every 1/30 second.

Each line has 680 pixels.

Lines are interleavedLines are interleaved

Every other Every other line is line is painted to painted to reduce flickerreduce flicker

Odd lines are Odd lines are ‘painted’ in ‘painted’ in 1/60 of a sec. 1/60 of a sec. followed by followed by even lines even lines painted next.painted next.

Inside of the Inside of the screen is coated screen is coated with stripes made with stripes made of three of three phosphors: They phosphors: They each glow red, each glow red, green, or blue.green, or blue.

Shadow Mask Shadow Mask ensures that each ensures that each beam strikes only beam strikes only the phosphor it the phosphor it was intended for.was intended for.

http://www.meko.co.uk/shadowmask.shtml

Colors are fused by the BrainColors are fused by the Brain

RGB can be mixed to create any color RGB can be mixed to create any color of varying intensity.of varying intensity.

TV broadcast uses Radio TV broadcast uses Radio SignalsSignals

Each station allocated 6 MHzEach station allocated 6 MHz 54 to 88 MHz for VHF channels 2 to 6 54 to 88 MHz for VHF channels 2 to 6 174 to 216 MHz for channels 7 174 to 216 MHz for channels 7

through 13 through 13 470 to 890 MHz for UHF channels 14 470 to 890 MHz for UHF channels 14

through 83 through 83

TV uses TV uses AM for videoAM for video and and FM for FM for audioaudio

www.sfu.ca/sonic-studio

Luminance (intensity), Luminance (intensity), Chromaticity (color), and soundChromaticity (color), and sound

Luminance for one lineLuminance for one line

Chrominance SignalChrominance Signal

Phase shift after sine wave Phase shift after sine wave determines color for one determines color for one pixel.pixel.

Recording onto tapeRecording onto tape

Video Head Drum is tilted with respect to the tape. This creates diagonal video tracks.

The drum rotates quickly, making long video tracks.

There are two record/read heads attached to the rotating drum.

One screen picture is two diagonal tracks, or one rotation of the drum.

Yellow tracks are audio and control tracks

Magnetic Data on TapeMagnetic Data on Tape

Control Track indicates if this is a SP, LP, or EP and thus determines how fast to pull the tape. It also ensures the heads are lined up correctly during playback.

Audio track is recorded and read similar to tape deck.

http://videoexpert.home.att.net/artic2/211vcrw.htm

TV goes Digital in Feb. 2009TV goes Digital in Feb. 2009 19.39-megabit-per-second (Mbps) 19.39-megabit-per-second (Mbps)

stream of digital data stream of digital data Multiple formats can be transmittedMultiple formats can be transmitted

Standard DefinitionStandard Definition High Definition (HDTV)High Definition (HDTV)

Digital Modulation Digital Modulation TechniquesTechniques

Phase Shift Keying (Bluetooth, Phase Shift Keying (Bluetooth, Wireless LANs)Wireless LANs)

Frequency Shift Keying (GSM Phones)Frequency Shift Keying (GSM Phones) Amplitude Shift Keying (Sending Amplitude Shift Keying (Sending

Morse Codes using Telegraph, optical Morse Codes using Telegraph, optical fibers send pulses of light fibers send pulses of light representing 1’s and 0’s)representing 1’s and 0’s)

Some Combination of the aboveSome Combination of the above

MonitorsMonitors

Cathode Ray Tube (CRT)Cathode Ray Tube (CRT) In most TVsIn most TVs Bulky, heavy, higher powerBulky, heavy, higher power Good color and displayGood color and display Image needs to be refreshedImage needs to be refreshed Warm-up time requirementWarm-up time requirement

Flat Panel (Liquid Crystal Display)Flat Panel (Liquid Crystal Display) More expensiveMore expensive Images may vary based on viewing angleImages may vary based on viewing angle Low PowerLow Power

Polarized vs. non-Polarized Polarized vs. non-Polarized LightLight

Light with the Electric Field in one orientation is polarized light.

http://www.geo.umn.edu

Liquid Crystal DisplaysLiquid Crystal Displays Glass plates are Glass plates are

electrodeselectrodes Applying a voltage Applying a voltage

across the plates across the plates aligns the liquid aligns the liquid crystals parallel to the crystals parallel to the voltagevoltage

Small one-directional Small one-directional scratches on the glass scratches on the glass plates cause the plates cause the crystals to twist when crystals to twist when there is no voltagethere is no voltage

http://en.wikipedia.org/wiki/Liquid_crystal_display

Polarizing FiltersPolarizing Filters

A thin film on a A thin film on a surface absorbs surface absorbs light with the light with the horizontal horizontal orientation.orientation.

Only light with a Only light with a non-horizontal non-horizontal orientation passes orientation passes through.through.

http://science.howstuffworks.com/sunglass2.htm

Liquid Crystal DisplaysLiquid Crystal DisplaysLCDs block light LCDs block light creating creating darknessdarkness

wikipedia

1. Vertical Polarizing Filter

2. 7-segment display with metal oxide that is both transparent & conductive. Backside has verticals ridges.

3. Liquid crystals

4. Layer with horizontal ridges

5. Horizontal Polarizing Filter

6. Reflective layer to reflect light back to your eye

LCD without voltage – light is passed through or reflected

LCD with applied voltage – light is blocked or absorbed by filters creating darkness.

Color is achieved with three sub-pixels: Red, Green, Blue

Voltage for each color determines intensity of the sub-pixel.

Color filters filter out all light but the one color for the sub-pixel.

SourcesSources

http://www.howstuffworks.com/tv.hthttp://www.howstuffworks.com/tv.htmm

http://www.physics.utoledo.edu/~lsa/http://www.physics.utoledo.edu/~lsa/_color/31_tv.htm_color/31_tv.htm