Coordinates	33°51′35.9″N151°12′40″N
{{infobox software| name	iMovie | logo 64px | screenshot 220px | caption iMovie '11 | developer Apple Inc. | latest_release_version 9.0.4 | latest_release_date | operating_system Mac OS X, iOS 4, Mac OS 9, Mac OS 8.6 | genre Video editing software | license Proprietary | website Apple iMovie Site }}

iMovie is a proprietary video editing software application which allows Mac, iPod Touch 4th generation, iPhone 4 and iPad 2 users to edit their own home movies. It was originally released by Apple in 1999 as a Mac OS 8 application bundled with the first FireWire-enabled consumer Apple model – iMac DV. Since version 3, iMovie has been a Mac OS X only application bundled in the iLife suite of Macintosh applications.

iMovie imports video footage to the Mac using either the FireWire interface on most MiniDV format digital video cameras, the USB port, or by importing the files from a hard drive. From there, the user can edit the video clips, add titles, and add music. Effects include basic color correction and video enhancement tools, and transitions such as fade-in, fade-out, and slides.

iMovie HD 5

iMovie HD includes support for HDV (720p and 1080i) and integration with the rest of the iLife suite, with toolbox buttons allowing the importing of images from iPhoto, music from iTunes and the setting of chapter markers ready for exporting to iDVD.

iMovie HD 5 imports mjpeg files as dv by default, which introduces noise; mjpeg files are cryptically lumped with "isight" files in this version.

Another new feature is the 'Magic iMovie', which attempts to automate the whole process of video editing, by allowing a common transition to be added between scenes, a music track to be synchronised with the video and a DVD to be created with the accompanying iDVD software.

iMovie HD 6

iMovie 6 was released in January 2006 as part of the iLife '06 suite and in iLife '08 as a substitution for iMovie '08 (due to the new version's incompatibility with older Power PC Macintosh computers). It was integrated with iPhoto, iTunes, iDVD, GarageBand and iWeb. iMovie 06 included new themes and was designed for ease of use, themes allow the user to drop movie clips or photos into professionally-designed backdrops. Each theme included full-motion graphic bumpers and transitions. iMovie 06 also contained Real-time effects which took advantage of the computer's graphic processing unit to perform some effects without rendering. iMovie 06 also contained Real-time titling, Enhanced audio tools and effects, Multiple open projects, Video podcasts and blogs (using integration with iWeb) and Refined look based on iTunes 5 and 6.

iMovie '08

iMovie '08 (Version 7.0) was released in August 2007 as a part of the iLife '08 suite. iMovie '08 was a complete redesign and rewrite of iMovie. It had much better HD output, and more formats to convert to. This was limited however by an undocumented restriction on supported codecs. iPhoto uses the QuickTime library and can create thumbnails for all QuickTime supported formats, but most of these cannot be used by iMovie '08. Indeed, even some of the very few formats that iMovie '08 is able to import will not be recognized when they are added to an iPhoto library. Though Motion JPEG encoded AVI files do appear to be recognized, this was the most common format used by digital cameras. The tile based editing interface was also promoted as something unique and groundbreaking, even though it is functionally identical to the interface of the Toaster Flyer non-linear digital editing systems released for Amiga computers by NewTek, Inc. in 1993. A new feature called ''skimming'' for quickly previewing video in the library at a user controlled speed was used, and so was a feature that allows one to highlight parts of video clips just like highlighting text. iMovie 08 also had the ability to add more than two layers of background sound, including multiple music, narration and sound effects; previous versions only had two spare audio tracks. It included more exportation formats with support for iPhone size video and many other sizes and supported non-tape based HD such as DVD camcorders HDD camcorders, & AVCHD. iMovie 08 also has the ability to export movies to Youtube.

According to Apple's system requirements iMovie '08 requires at least a PowerPC G5 1.9 GHz or an Intel Processor. G4s are not supported, though Apple sold its last G4-based Computers (iBook G4) 14 months before the release of iLife '08. However, a system hack enables iMovie 7.1 or higher to run on a PowerPC G4.

Criticism of iMovie '08

iMovie 08 was criticized due to a drastic abandonment of some iMovie HD 6 features. New York Times reviewer David Pogue said "iMovie ‘08 is an utter bafflement... incapable of the more sophisticated editing that the old iMovie made so enjoyable...All visual effects are gone—even basic options like slow motion, reverse motion, fast motion, and black-and-white. And you can’t have more than one project open at a time."

Features removed included the classic timeline, the ability to create DVD chapter markers, support for plugins, and in-timeline audio adjustment and control. Most surprisingly, iMovie '08 imports a much more limited set of video codecs and metadata formats than previous versions of iMovie or today's QuickTime Player. For example, QuickTime Player can be extended to support the FLIP Video 3ivx MPEG-4 codec, but iMovie cannot. Limited import formats also excludes the DV format for storing raw format. As a result, all resulting videos have lossy compression applied and there is no facility for managing full format video. The peculiar lack of QuickTime support means QuickTime Pro can edit a far larger range of video than iMovie '08.

Apple released iMovie HD 6 as a free download to those who had purchased iMovie '08. However, in response to the release of the subsequent newer version of iMovie '09, Apple removed that official iMovie HD 6 download in late January 2009 while Apple also reduced the price tag for Final Cut Express. Several of the features removed from iMovie '08 that were previously in iMovie HD 6 have been restored into iMovie '09 and more recently iMovie '11.

iMovie '09

iMovie '09 (Version 8.0) was released January 2009 as part of the iLife '09 package. It introduced some new features and restored some features from previous versions of iMovie, including basic video effects (such as fast/slow motion and aged film) and image stabilization as well as travel map functions for marking locations where a video was shot. iMovie '09 also introduced simple implementations of more advanced features such as picture-in-picture and greenscreening. It also improved editing (with a precision cut editor and a clip trimmer), improved support for hard drive based cameras (such as the Flip Mino), added some new titles and transitions, and added full iDVD support which was unavailable in iMovie '08. It now has Full-Screen Library Browser via which you can find and examine all your video in one place. However, it is still lacking in several of the effects that iMovie HD 6 had, leaving out simple effects such as "lightning". Like iMovie '08 it is not supported on PowerPC G4 computers, although hacks are again available that will allow it to run on any G4 provided that it has a Core Image-capable video card.

iMovie '11

iMovie '11 (Version 9.0) was released on October 20, 2010 as part of the iLife '11 package. It has the ability to make trailers for home movies, more control over audio, instant replays, flash and hold, facial recognition, news themes, and the ability to watch the video on a Mac, iPad, iPhone/iPod touch, Apple TV, Facebook and YouTube. It now supports the AVCHD Lite format.

Apple worked with Abbey Road Studios in London, England to bring original music/film scores to iMovie '11. Most notable is the music used in the "trailers" feature provided by the software.

iMovie for iOS

On June 7, 2010, Steve Jobs announced in the WWDC keynote that the upcoming iPhone 4 would support an iOS-native version of iMovie that supports many of the basic features which are available in the Mac OS X version of the software. The App may be obtained by downloading it from the App Store for iMovie for iPhone was available June 24, 2010 to coincide with the launch of the iPhone 4. On September 1, 2010, iMovie was made compatible with the 4th generation iPod Touch. iMovie will be made available with the release of iPad 2, announced on March 2, 2011 during Apple's held media event at the Yerba Buena Center for the Arts in San Francisco. The new version was released on March 10, 2011.

Version history

!Version	!Release date	!Availability	!System	!Notes
iMovie	October 5, 1999	Bundled with iMac DV, later issued as a free download.	Mac OS 8.6 and OS 9
iMovie 2	July 19, 2000	Bundled with FireWire-enabled Macs, also a separate purchase and later bundled as part of Mac OS X.	Mac OS 9 and OS X	Added new sound effects (including some from Skywalker Sound), but removed older ones; also removed the Water Ripple effect.
iMovie 3	January 7, 2003	Bundled with all new Macs, also a separate purchase (iLife), later as a free download.	Mac OS X	Bundled as part of iLife.
iMovie 4	January 6, 2004	Bundled with all new Macs, also a separate purchase (iLife '04).	Mac OS X	Bundled as part of the iLife '04 package.
iMovie HD 5	January 6, 2005	Bundled with all new Macs, also a separate purchase (iLife '05).	Mac OS X	Bundled as part of the iLife '05 package.
iMovie HD 6	January 10, 2006	Bundled with all new Macs and separate purchase (iLife '06), later as free download for owners of iLife '08.	Mac OS X 10.3 (Panther), Mac OS X 10.4 (Tiger), Mac OS X 10.5 (Leopard) and Mac OS X 10.6 (Snow Leopard)	Bundled as part of the iLife '06 package.
iMovie '08	August 7, 2007	Bundled with all new Macs and for separate purchase (iLife '08).	Mac OS X 10.4 (Tiger) and 10.5 (Leopard).	Bundled as part of the iLife '08 package. Redesigned.
iMovie '09	January 27, 2009	Bundled with all new Macs and for separate purchase (iLife '09).	Mac OS X 10.5 (Leopard) and Mac OS X 10.6 (Snow Leopard)	Bundled as part of the iLife '09 package.
iMovie for iPhone and iPod Touch	June 24, 2010	Available to purchase in the Apple App Store.	iOS 4
iMovie '11	October 20, 2010	Bundled with all new Macs sold on or after October 20, 2010 or for separate purchase in iLife '11.	Mac OS X Snow Leopard (10.6.3 and later)	Bundled as part of the iLife '11 package. Also available for purchase in the Mac App Store.
iMovie for iPad	March 10, 2011	Available to purchase in the iOS App Store.	iOS 4.3

References

External links

Apple: iMovie

Category:Video editing software Category:Mac OS X-only software made by Apple Inc.

da:IMovie de:IMovie es:IMovie fr:IMovie ko:아이무비 is:IMovie it:IMovie hu:IMovie nl:IMovie ja:IMovie no:IMovie pl:IMovie pt:IMovie ru:IMovie fi:IMovie sv:Imovie zh:IMovie

Chroma key compositing (or chroma keying) is a technique for compositing (layering) two images together. A color range in the top layer is made transparent, revealing another image behind. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, color-separation overlay (CSO; primarily by the BBC), greenscreen, and bluescreen. It is commonly used for weather forecast broadcasts, wherein the news presenter appears to be standing in front of a large map during live television newscasts, but in a television studio it is actually a large blue or green background. The meteorologist stands in front of a bluescreen, and then different weather maps are added on those parts in the image where the color is blue. If the meteorologist wears blue clothes, his clothes will become replaced with the background video. This also works for greenscreens, since blue and green are considered the colors least like skin tone. This technique is also used in the entertainment industry, for example for special effects.

History

For filmmaking, a complex and time consuming process once known as "travelling matte" was used prior to the introduction of digital compositing. The blue screen and traveling matte method were developed in the 1930s at RKO Radio Pictures and other studios, and were used to create special effects for ''The Thief of Bagdad'' (1940). At RKO, Linwood Dunn used a travelling matte to create "wipes" – where there were transitions like a windshield wiper in films such as ''Flying Down to Rio'' (1933).

The credit for development of the bluescreen is given to Larry Butler, who won the Academy Award for special effects for ''The Thief of Bagdad''. He had invented the blue screen and traveling matte technique in order to achieve the visual effects which were unprecedented in 1940. He was also the first special effects man to have created these effects in Technicolor, which was in its infancy at the time.

In 1950, Warner Brothers employee and ex-Kodak researcher Arthur Widmer began working on an ultra violet traveling matte process. He also began developing bluescreen techniques: one of the first films to use them was the 1958 adaptation of the Ernest Hemingway novella, ''The Old Man and the Sea'', starring Spencer Tracy.

The background footage is shot first and the actor or model is filmed carrying out their actions against a bluescreen. To simply place the foreground shot over the background shot would create a ghostly image over a blue-tinged background. The actor or model must be separated from the background and placed into a specially-made "hole" in the background footage. The bluescreen shot was first rephotographed through a blue filter so that only the background is exposed. A special film is used that creates a black and white negative image — a black background with a subject-shaped hole in the middle. This is called a 'female matte'. The bluescreen shot was then rephotographed again, this time through a red and green filter so that only the foreground image was cast on film, creating a black silhouette on an unexposed (clear) background. This is called a 'male matte'.

thumb|right|Example of a basic blue screen set.The background image is then rephotographed through the male matte, and the shot rephotographed through the female matte. An optical printer with two projectors, a film camera and a 'beam splitter' combines the images together one frame at a time. This part of the process must be very carefully controlled to ensure the absence of 'black lines'. During the 1980s, minicomputers were used to control the optical printer. For ''The Empire Strikes Back'', Richard Edlund created a 'quad optical printer' that accelerated the process considerably and saved money. He received a special Academy Award for his innovation.

One drawback to the traditional traveling matte is that the cameras shooting the images to be composited can't be easily synchronized. For decades, such matte shots had to be done "locked-down" so that neither the matted subject nor the background could shift their camera perspective at all. Later, computer-timed motion control cameras alleviated this problem, as both the foreground and background could be filmed with the same camera moves.

Petro Vlahos was awarded an Academy Award for his development of these techniques. His technique exploits the fact that most objects in real-world scenes have a color whose blue color component is similar in intensity to their green color component. Zbigniew Rybczyński also contributed to bluescreen technology.

For ''Star Trek: The Next Generation'', an ultraviolet light matting process was proposed by Don Lee of CIS and developed by Gary Hutzel and the staff of Image G. This involved a fluorescent orange backdrop which made it easier to generate a holdout matte, thus allowing the effects team to produce effects in a quarter of the time needed for other methods.

Some films make heavy use of chroma key to add backgrounds that are constructed entirely using computer-generated imagery (CGI). Performances from different takes can even be composited together, which allows actors to be filmed separately and then placed together in the same scene. Chroma key allows performers to appear to be in any location without even leaving the studio.

Computer development also made it easier to incorporate motion into composited shots, even when using handheld cameras. Reference-points can now be placed onto the colored background (usually as a painted grid, X's marked with tape, or equally spaced tennis balls attached to the wall). In post-production, a computer can use the references to adjust the position of the background, making it match the movement of the foreground perfectly. Modern advances in software and computational power have even eliminated the need to use grids or tracking marks – the software analyzes the relative motion of colored pixels against other colored pixels and solves the 'motion' to create a camera motion algorithm which can be used in compositing software to match the motion of composited elements to a moving background plate.

Weathermen often use a field monitor to the side of the screen to see where they are putting their hands. A newer technique is to project a faint image onto the screen.

The process

The principal subject is filmed or photographed against a background consisting of a single color or a relatively narrow range of colors, usually blue or green because these colors are considered to be the furthest away from skin tone. The portions of the video which match the preselected color are replaced by the alternate background video. This process is commonly known as "keying", "keying out" or simply a "key".

Green is currently used as a backdrop more than any other color because image sensors in digital video cameras are most sensitive to green, due to the bayer pattern allocating more pixels to the green channel, mimicking the human eye's increased sensitivity to green light. Therefore, the green camera channel contains the least "noise" and can produce the cleanest key/matte/mask. Additionally, less light is needed to illuminate green, again because of the higher sensitivity to green in image sensors. Bright green has also become favored as a blue background may match a subject's eye color or common items of clothing, such as jeans, or a dark-navy suit.

Blue was used before digital keying became commonplace because it was necessary for the optical process, but it needed more illumination than green. However, it is also further in the visual spectrum from red, the predominant color in human skin.

The most important factor for a key is the color separation of the foreground (the subject) and background (the screen) – a bluescreen will be used if the subject is predominately green (for example plants), despite the camera being more sensitive to green light.

In analog color TV, color is represented by the phase of the chroma subcarrier relative to a reference oscillator. Chroma key is achieved by comparing the phase of the video to the phase corresponding to the preselected color. In-phase portions of the video are replaced by the alternate background video.

In digital color TV, color is represented by three numbers (red, green, blue). Chroma key is achieved by a simple numerical comparison between the video and the preselected color. If the color at a particular point on the screen matches (either exactly, or in a range), then the video at that point is replaced by the alternate background video.

Clothing

A chroma key subject must not wear clothing similar in color to the chroma key color(s) (unless intentional), because the clothing may be replaced with the background video. An example of intentional use of this is when an actor wears a blue covering over a part of his body to make it invisible in the final shot. This technique can be used to achieve an effect similar to that used in the ''Harry Potter'' films to create the effect of an invisibility cloak. The actor can also be filmed against a chroma key background and inserted into the background shot with a distortion effect in order to create a cloak that is marginally detectable.

Difficulties emerge with bluescreen when a costume in an effects shot must be blue, such as Superman's traditional blue outfit. In the 2002 film ''Spider-Man'', in scenes where both Spider-Man and the Green Goblin are in the air, Spider-Man had to be shot in front of the greenscreen and the Green Goblin had to be shot in front of a bluescreen, because Spider-Man wears a costume which is red and blue in color and the goblin wears a costume which is entirely green in color. If both were shot in front of same screen, one character would have been partially erased from the shot.

Background

Blue is generally used for both weather maps and special effects because it is complementary to human skin tone. The use of blue is also tied to the fact that the blue emulsion layer of film has the finest crystals and thus good detail and minimal grain (in comparison to the red and green layers of the emulsion.) In the digital world, however, green has become the favored color because digital cameras retain more detail in the green channel and it requires less light than blue. Green not only has a higher luminance value than blue but also in early digital formats the green channel was sampled twice as often as the blue, making it easier to work with. The choice of color is up to the effects artists and the needs of the specific shot. In the past decade, the use of green has become dominant in film special effects. Also, the green background is favored over blue for outdoors filming where the blue sky might appear in the frame and could accidentally be replaced in the process. Although green and blue are the most common, any color can be used. Red is usually avoided due to its prevalence in normal human skin pigments, but can be often used for objects and scenes which do not involve people.

Occasionally, a magenta background is used, as in some software applications where the magenta or fuchsia key value #FF00FF is sometimes referred to as "magic pink".

With better imaging and hardware, many companies are avoiding the confusion often experienced by weather presenters, who must otherwise watch themselves on a monitor to see the image shown behind them, by lightly projecting a copy of the background image onto the blue/green screen. This allows the presenter to accurately point and look at the map without referring to monitors.

A newer technique is to use a retroreflective curtain in the background, along with a ring of bright LEDs around the camera lens. This requires no light to shine on the background other than the LEDs, which use an extremely small amount of power and space unlike big stage lights, and require no rigging. This advance was made possible by the invention of practical blue LEDs in the 1990s, which also allow for emerald green LEDs.

There is also a form of color keying that uses light spectrum invisible to human eye. Called Thermo-Key, it uses infrared as the key color, which would not be replaced by background image during postprocessing.

Even lighting

The biggest challenge when setting up a bluescreen or greenscreen is even lighting and the avoidance of shadow, because it is best to have as narrow a color range as possible being replaced. A shadow would present itself as a darker color to the camera and might not register for replacement. This can sometimes be seen in low-budget or live broadcasts where the errors cannot be manually repaired. The material being used affects the quality and ease of having it evenly lit. Materials which are shiny will be far less successful than those that are not. A shiny surface will have areas that reflect the lights making them appear pale, while other areas may be darkened. A matte surface will diffuse the reflected light and have a more even color range. In order to get the cleanest key from shooting greenscreen it is necessary to create a value difference between the subject and the greenscreen. In order to differentiate the subject and screen a two-stop difference can be used, either by making the greenscreen two stops higher than the subject or vice versa.

Sometimes a shadow can be used to create a special effect. Areas of the bluescreen or greenscreen with a shadow on them can be replaced with a darker version of the desired background video image, making it look like the person casting the shadow is actually casting a shadow on the background image instead.

Another common, related, problem is lighting the subjects in a manner that is complementary to the scene being keyed in behind. Attention has to be paid to matching the direction of lighting and the color balance in the background. Any spill of the chroma key color will make the result look unnatural. Even a difference in the focal length of the lenses used can affect the success of chromakey.

Exposure

Another challenge for bluescreen or greenscreen is proper camera exposure. Underexposing or overexposing a colored backdrop can lead to poor saturation levels. In the case of video and digital cinema cameras, underexposed images can contain high amounts of noise, as well. The background must be bright enough to allow the camera to create a bright and saturated image.

Programming

There are several different quality- and speed-optimized techniques for implementing color keying in software.

In most versions, a function ''f''(''r'', ''g'', ''b'') → ''α'' is applied to every pixel in the image. α (alpha) has a meaning similar to that in alpha compositing techniques. ''α'' ≤ 0 means the pixel is the green screen, ''α'' ≥ 1 means the pixel is in the foreground object. Values between 0 and 1 indicate a pixel that is partially covered by the foreground object. A usable green screen example, which matches how chroma key was done on an optical printer, is ''f''(''r'', ''g'', ''b'') = ''K₀'' * ''b'' − ''K₁'' * ''g'' + ''K₂'' (''K_0..2'' are user-adjustable constants, 1 is a good initial guess for all of them).

Often the software does screen spill removal from the colors as well as figure out the alpha. This may be a separate function ''g''(''r'', ''g'', ''b'') → (''r'', ''g'', ''b''), a very simple green screen example is ''g''(''r'', ''g'', ''b'') → (''r'', ''min''(''g'', ''b''), ''b''). Or ''f'' is changed to return (''r'', ''g'', ''b'', ''a'') all at once, this is useful if part of the calculation is shared.

Most keyers use far more complicated functions. A popular approach is to describe a closed 3D surface in RGB space and determine the signed distance the point (''r'', ''g'', ''b'') is from this surface, or to find the distance the point (''r'', ''g'', ''b'') is between two closed nested surfaces. It is also very common for ''f''() to depend on more than just the current pixel's color, it may also use the (''x'', ''y'') position, the values of nearby pixels, the value from reference images, and values from user-drawn masks.

A different class of algorithm tries to figure out a 2D path that separates the foreground from the background. This path can be the output, or the image can be drawn by filling the path with ''α'' = 1 as a final step. An example of such an algorithm is the use of active contour. Most research in recent years has been into these algorithms.

See also

Compositing

Federal Standard 1037C

Filmmaking

''Drew Carey's Green Screen Show''

Film production

Front projection effect

Live action

Matte (filmmaking)

Muslin

Optical printer

Primatte chromakey technology

Rear projection effect

Reverse bluescreen

Schüfftan process

Signal processing

Sodium vapor process

Special effects

Video switcher

Virtual set

References

External links

Building a Chroma Key on a low budget (Google Knol)

How Blue Screens Work

Stargate Studios Virtual Backlot Reel 2009 -- A demonstration of green screen scenes

Category:Film and video technology Category:Television terminology

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