Clarke, R. J (2001) L213-05: 1

Multimedia in Organisations

BUSS 213

Lecture 5Media 3: Temporal Media-

Sound and Video

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Notices (1)General

Lab 5 is transferred to Lab 6 effective from today (24/8/01) till the end of session (so that we can make use of machines with more memory and usable sound facilities)

this week tutorial sheet is available on this site for use in the laboratory (open up WORD or simply print it out)

Assignment 1 is due today BUSS213 is supported by a website, where you can

find out the latest Notices and get Lecture Notes, Tutorial Sheets, Assignments etcwww.uow.edu.au/~rclarke/buss213/buss213.htm

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Notices (2)Assignment 2

Assignment 2 will be available from the BUSS213 Intranet on Monday (you have the week end to catch your breath): it involves creating a Multimedia Presentation for a

Concept, Service, Place or Product. use internet to gather material (which must be credited).

You write the text, design and implement the presentation. the best movies will go into a gallery on the BUSS213

website. This assignment will be a Director project in Version 5 Academic only!

you must send me your topic in an e-mail called A2-213-01 only this time you have one (1) week to send this email

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Agenda (1)

in this third lecture on media we consider various topics relevant to sounds and images- temporal media

Again the rationale for having lectures on separate types of media is that it is necessary to understand individual media in detail before we consider how to combine them

this is such a huge topic that the contents of this lecture are very selective! we will not consider in this lecture different types of

bradcast video standards, integrating computers and television, or recording formats- read the text and yes it is examinable

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Agenda (2)Topics in this Lecture & Related Readings

we will discuss: Video

Video Basics Shooting and Editing Video Digital Video

we will not discuss audio- we simply don’t have the time- but it is important that you understand it, read about: Audio

Audio Basics Digital Audio Production Aspects

Related Readings Vaughan (1998) Chapter

10: Sound, 241-282 and Chapter 13: Video 339-368

as with all specified reading- these are examinable material

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Video Basics

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Video Basics Additive and Subtractive Colour Schemes

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Analog Camera TechnologiesRGB colour video camera system

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Analog Camera TechnologiesSingle sensor colour video camera system

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Video BasicsAnalog Artifacts

Standard analogue video contains many problems- one of these is a set of problems called artifacts

if you are intending to create digital multimedia and you are using analog video sources then artifacts effect the quality of the result and can adversely effect compression of the final digital form

Various types of artifact include: Noise, RF Interference, Loss of high frequencies, smear, streaking, colour fringing, colour balance errors, colour saturation errors, flag waving, and jitter

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Analog ArtifactsNoise & RF Interference

Noise (shown on the left): the most common form of noise is called ‘snow’ as seen on your TV- it is specked appearance- if it is uniformly distributed over the full bandwidth of the video signal then it is called white noise (or flat noise)

RF Interference: Various kind of coherent (not random) interferences will depend on the exact frequency relationship they have to the scanning frequencies

(simulated noise)

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Analog Artifacts Loss of high frequencies

in composite colour television, the first effect of loss of high frequencies is that colour saturation- vividness of the colour- is reduced or colour is completely lost

Severe loss of high frequencies will noticeably affect the sharpness of vertical edges in images

In RGB systems loss of high frequencies affects sharpness although not uniformly in all separate channels

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Analog Artifacts Smear

shows up as picture information which is smeared to the right (usually) it is cause by a loss of amplitude or a phase shift at frequencies near or so what above the horizontal line frequency

tube based camera have a high peaker adjustment which can cause this distortion if not correctly set

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Analog Artifacts Streaking

Streaking is present when a bright object in the image causes a shifting of brightness all the way across the image at the vertical location of the bright object

Usually caused by video information which gets into the blanking interval and interferes with circuits in the video equipment

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Analog Artifacts Colour Fringing

when edges in the pictures have colours not present in the originals scenes- the principal cause of which is registration errors in cameras- generally the colour fringing occurs through the image

other possible causes include distortions introduced during recording- in which case the unwanted colours occur only in vertical edges

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Analog ArtifactsColour Balance Errors

In RGBs system, the most likely colour errors are caused by the video levels not being the same in each of the three channels- this type of error originates at the camera

Colour balance errors show up as an ‘unnatural’ constant colour over the entire image independent of which colours are used in a scene- sometimes this is called a cast (not to be confused with Director)

Possibly the operator did not go through a colour balance procedure (for those camera that automatically white balance- almost all of them- this procedure involves either pointing the camera at a flat white surface or using a white opaque lens cap)

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Analog Artifacts Colour Saturation Errors

affects any composite video systems- those where three distinct video signals (Red Green Blue or RGB) are encoded into a ‘composite’ signal in order to be distributed onto a single cable

colour saturation errors can most commonly be caused by an incorrect high frequency response in the composite signal which effects the amplitude of the colour sub-carrier

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Analog Artifacts Flag Waving

In low cost recorders there can be a problem of synchronisation instability at the top of the picture called flag waving

Shows up as vertical edges at the top of the screen moving left to right from their correct position

Caused when the video playback head has to leave the tape at one edge and come back onto the tape at the other edge (helical scanning means that video information is written in diagonal strips along the video tape)- if the tape is not tensioned correctly flag waving occurs although video recorders can have a skew control which adjusts tape tension

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Analog ArtifactsJitter

with jitter, the entire picture shows a random motion from left to right caused by time base errors from the video recorder in video recorders the smoothness of the

mechanical motion of the recorders head drum is very crucial to reproducing a stable picture

Higher priced recorders use a Time Base Corrector (TBC) to correct this problem

Occasionally jitter effects are caused by other kinds of defects or interferences getting into the synchronizing signals or circuits

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Digital Video

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Analog to Digital Conversion24 bits per pixel (bpp)

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Image DigitisationEffect of the Numbers of Pixels

the eye is tolerant to reducing the numbers of pixels in an image

the original 520 x 480 image is clear, but making the number of pixels to 128 x 120 makes the image fuzzy but still recognisable with only 1/16 the size

at 64 x 60 pixels the smallest image size has a very grainy look

512 x 480 pixels

128 x 120 pixels 64 x 60 pixels

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Image Digitisation Effect of Bits/Pixel

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Image Digitisation Text Anti-aliasing

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Digital Video

Dealing with digital video only is the ultimate in video processing, however…

…it is not yet common place to have digital video cameras, and so…

…the current state of the art is that you typically record using analog video (in the so-called analog domain) but complete all other stages are completed digitally (in the so-called digital domain) including editing and post-production (cleaning up the images, colour matching, special effects)

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Digital VideoAnalog Broadcast Cameras are very good

in fact, our experience with using side-by-side comparisons (sometimes referred to as AB comparisons) is that broadcast quality analog video cameras can provide ‘better looking’ video in the same conditions as ‘pro-sumer grade’ digital video cameras BetaCams (analog broadcast quality cameras) can be calibrated

to work in low light levels- in dark environments this means that camera can distinguish between different levels of black- this is more than just an issue of sensitivity its about the quality of black- it looks ‘softer’ or warmer

Digital Video Cameras can also reach into these dark levels but they appear to flatten out or equalise the differences- the effect is harsh and ‘flat’- more like watching cartoons- these effects are subtle but you can see them if you look!

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Digital Video Converting from Analog Video

if you have analog video: recorded on a VCR at home, sourced from

broadcasts or from your own analog video cameras- this will need to be converted to digital information

the process of conversion is called video digitisation (or simply digitising) and the equipment used to do it is referred to as video digitiser (or simply digitiser)

with digitisers you pay for good quality you want to be able to sample the video stream at least four times higher than the frame rate- that is really fast because video is made up of 25 frames a second

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Digital Video Playback- Architecture

the resulting digital video clip can be stored as data on a hard disk, CD-ROM, DVD, or other mass-storage device without the use of other digital equipment

the playback is provided by software architectures: Microsoft’s Active Movie for Windows

(previously Video for Windows) Apple’s QuickTime

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Digital Video Playback- Architecture

we will briefly describe QuickTime- no serious attempt at commercial multimedia system would use anything else other than this product the authoring or development environment is only

available on Apple systems, this might seem to be a problem but in fact for a very

long time Apple systems have been the first and only choice when considering development platforms

it was only with the release of NT and 2000 than many of the major multimedia development packages became available to IBM PC users (eg. Adobe Suite products etc)

QuickTime clips can be played on any platform and they can be streamed on the Internet

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Shooting VideoStatic & Dynamic Composition

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Shooting VideoLayout or Static Composition

in this set of slides we will consider some of the conventions used in the layout or composition of a single image- so this discussion applies equally to photography and animation as it does for videography

the term layout- or static composition- refers to or the organisation of static components like background elements, props, position of actors or characters, and camera viewpoint etc.

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Shooting VideoSemiotics of the Frame (1)

the discipline of semiotics concerns itself with understanding meanings

in traditional and digital forms of animation, photography, cinematography and videography, placing a frame is a semiotic act because you are selecting some visual elements and excluding others

the camera operator does not facilitate your interpretation of the images rather the camera operator mediates your interpretation

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Shooting VideoSemiotics of the Frame (2)

an excluded elements in a scene literally does not exist for the audience …

… while the audience is confronted with only those visual elements of the scene which the camera operator considers relevant

skillful camera work involves the camera technician continuously deciding which elements to include in the frame and…

… anticipates the effect of these on the audience’s interpretation of the scene

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Shooting VideoRules of Composition (1)- Centres of Interest Composition refers to the relationship between the main subject – the

person or object of interest – within the frame it affects our perceptions of the scene and how the audience will view

and receive the worlds constructed for us by the camera operator the rule of thirds (below) avoids compositions where all the elements

are perfectly balanced (symmetrical balance), applied to the frame this rule produces four so-called centres of interest

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Shooting VideoRules of Composition (2)

Action or line of sight towards frame right should be positioned frame left and vice versa for ‘nose room’

Create illusion of depth by having objects in foreground, middle ground and background

Always zoom in to full telephoto to adjust focus

Allow for image cut-off around frame edges. Keep the important parts of the image towards frame centre

Fill the whole screen with the most important and significant subject matter

Empty space is wasted space Avoid tilted horizontal and vertical

lines Movement or bright lights in the

background are distracting If the background proves

problematic during shooting, it will be worse for your audience. Move the camera or the subject before taping

When shooting people, place the subject’s eyes one-third down from the top of the frame matter the type of shot

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Shooting VideoRules of Composition (3)- Horizon Line

Most scenes should use a 1/3rd ground, 2/3rd sky layout which allows propos and backdrop details to be seen while allowing apace for characters to remain the central attraction (left)

Occasionally the 2/3rd ground, 1/3rd sky rule is used which is the same as tilting the camera down- its effect is to add a sense of dramatic urgency so don’t overdo it (right)

Scenes shot outdoors or in a large room need a horizon line where the ‘sky’ meets the ‘floor’the horizon line should not be in the middle of the frame which results in an awkward layout for the objects in the scene

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Shooting VideoLong, Mid, Close-up & Extreme Close-ups

Long Shot (LS)- the establishing Shot is the shot of the subject/s taken

from a distance away in order to show the subject/s relation to their physical surroundings

Mid Shot (MS)- the action shot the shot used to show any

action occurring the subject is still seen in

relation to their surroundings, yet there is still enough space in the frame to show dialogue or other interactions between characters

Close-Up (CU)- reaction shot often focuses entirely on the

subjects face and their face only

used to convey emotion and are centred on the subject

Extreme Close-Up (ECU)- the emotion shot crop the top of the head and

chin and focus on the eyes and mouth

as with CU’s, ECU’s convey emotion and are centred entirely on the subject

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Shooting VideoLong, Mid, Close-up & Extreme Close-ups

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Shooting VideoShot Framing- One Subject Scene

the example on the right is correct- it conforms to the rules of composition- centres of interest described earlier

avoid the symmetrical balance of the middle example avoid cramping the subject’s face up against the frame on

the left hand example

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Shooting Video Shot Framing- Two Subject Framing

the layout of the upper left frame is often used by amateurs

upper right hand frame is more interesting

however shots can and should be varied like those used in the lower frames

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Shooting VideoPoor Composition- Ambiguous Lines

a number of problems that can result from poor composition are shown below

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Shooting VideoStaging or Dynamic Composition

staging refers to dynamic effects like character movement and camera movement (including pans and zooms)

come is a number of varieties: Zoom in/out: not a true move but a lens change from wide

angle (LS) to telephoto (CU) Pan and tilt: pans move the camera horizontally (side to side),

tilt moves the camera vertically Track: you move the entire camera to follow a moving subject Truck: the subject is stationary but the camera moves Dolly: moves the camera towards (dolly in) or away (dolly out)

from the subject- a dolly shot changes visual perspective because the camera is moving through the scene

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Shooting VideoStaging or Dynamic Composition

How fast should dynamic movement be- no faster than the movement of the second hand on you watch

Any faster and the action will blur, and this will likely make your viewer disoriented at best and nauseous at worse

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Video Technologies

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Video Production WorkflowStages and Typical Technologies

Camera Work

Shooting Post-Production

DigitalEditing Compression

On-lineOff-line

EffectTransitionsTitling

FormattingCompressingDelivery

PremierFinal Cut Pro

After Effects Media Cleaner Pro Sorenson

Analogue or Digital

See also detail on Digital Editing Workflow in Lecture BUSS213-12a