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This lecture discusses various topics related to sound and video in temporal media, including video basics, shooting and editing video, digital video, analog artifacts, and more.
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Multimedia in Organisations BUSS 213 Lecture 5 Media 3: Temporal Media- Sound and Video
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 • BUSS213is supported by a website, where you can find out the latest Notices and get Lecture Notes, Tutorial Sheets, Assignments etc www.uow.edu.au/~rclarke/buss213/buss213.htm
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 calledA2-213-01 only this time you have one (1) week to send this email
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
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 Agenda (2)Topics in this Lecture & Related Readings
Analog Camera TechnologiesSingle sensor colour video camera system
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
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 Analog ArtifactsNoise & RF Interference (simulated noise)
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
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 Analog Artifacts Smear
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 Analog Artifacts Streaking
Analog Artifacts Colour Fringing • when edges in the pictures have colours not present in the originals scenes- the principal cause of which is registrationerrors 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
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)
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
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
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
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 Image DigitisationEffect of the Numbers of Pixels 64 x 60 pixels 128 x 120 pixels
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)
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!
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
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
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
Shooting VideoLayout or Static Composition • in this set of slides we will consider some of the conventions used in thelayout 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.
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
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
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 Shooting VideoRules of Composition (1)- Centres of Interest
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 Shooting VideoRules of Composition (2)
Shooting VideoRules of Composition (3)- Horizon Line • 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 • 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)
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 Shooting VideoLong, Mid, Close-up & Extreme Close-ups
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
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 Shooting Video Shot Framing- Two Subject Framing
Shooting VideoPoor Composition- Ambiguous Lines • a number of problems that can result from poor composition are shown below
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
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
Post-Production Digital Editing Video Production WorkflowStages and Typical Technologies Effect Transitions Titling Formatting Compressing Delivery On-line Off-line Camera Work Shooting Compression After Effects Media Cleaner Pro Sorenson Analogue or Digital Premier Final Cut Pro See also detail on Digital Editing Workflow in Lecture BUSS213-12a
