Misplaced Pages

#435564

97-423: DV (from Digital Video ) is a family of codecs and tape formats used for storing digital video , launched in 1995 by a consortium of video camera manufacturers led by Sony and Panasonic . It includes the recording or cassette formats DV, MiniDV, DVCAM, Digital8 , HDV , DVCPro, DVCPro50 and DVCProHD. DV has been used primarily for video recording with camcorders in the amateur and professional sectors. DV

194-598: A "key". Green is used as a backdrop for TV and electronic cinematography more than any other colour because television weather presenters tended to wear blue suits. When chroma keying first came into use in television production, the blue screen that was then the norm in the movie industry was used out of habit, until other practical considerations caused the television industry to move from blue to green screens. Broadcast-quality colour television cameras use separate red, green and blue image sensors, and early analog TV chroma keyers required RGB component video to work reliably. From

291-438: A .wav or .aiff file) has long been a standard across multiple platforms, but its transmission over networks is slow and expensive compared with more modern compressed formats, such as Opus and MP3. Many multimedia data streams contain both audio and video , and often some metadata that permits synchronization of audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for

388-462: A Firewire to Thunderbolt adapter - this can be particularly useful for capturing on modern laptop computers which usually do not have a FireWire port or expansion slot but always have USB or Thunderbolt ports. Codec In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or data stream, and hence is a type of codec. Endec is a portmanteau of encoder/decoder . A coder or encoder encodes

485-480: A background from the subject of a photo or video – particularly the newscasting , motion picture , and video game industries. A colour range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as colour keying , colour-separation overlay ( CSO ; primarily by

582-427: A bright and saturated image. There are several different quality- and speed-optimised techniques for implementing colour 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 fully in the green screen, α  ≥ 1 means

679-540: A capacity of 252 minutes of DVCPRO video or 126 minutes of DVCPRO50 or DVCPRO HD-LP video. With proliferation of tapeless camcorder video recording, DV video can be recorded on optical discs , solid state flash memory cards and hard disk drives and used as computer files . In particular: Video is stored either as native DIF bitstream or wrapped into an audio/video container such as AVI , QuickTime or MXF . Nearly all DV camcorders and decks have IEEE 1394 (FireWire, i.LINK) ports for digital video transfer. This

776-478: 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 blue screen 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

873-425: A complete digital copy of what has been recorded onto tape. If needed, the video can be recorded back to tape to create a full and lossless copy of the original footage. Some camcorders also feature a USB 2.0 port for computer connection. This port is usually used for transferring still images, but not for video transfer. Camcorders that offer video transfer over USB usually do not deliver full DV quality; usually it

970-463: A computer can use these markers to compute the camera's position and thus render an image that matches the perspective and movement of the foreground perfectly. Modern advances in software and computational power have eliminated the need to accurately place the markers ⁠— ⁠the software figures out their position in space; a potential disadvantage of this is that it requires camera movement, possibly contributing to modern cinematographic techniques whereby

1067-649: A data stream or a signal for transmission or storage, possibly in encrypted form, and the decoder function reverses the encoding for playback or editing. Codecs are used in videoconferencing , streaming media , and video editing applications. In the mid-20th century, a codec was a device that coded analog signals into digital form using pulse-code modulation (PCM). Later, the name was also applied to software for converting between digital signal formats, including companding functions. An audio codec converts analog audio signals into digital signals for transmission or encodes them for storage. A receiving device converts

SECTION 10

#1732863135436

1164-416: A default value of 1.0. A very simple g () is ( r , min( g , b ), b ). This is fairly close to the capabilities of analog and film-based screen pulling. Modern examples of these functions are best described by two closed nested surfaces in 3D RGB space, often quite complex. Colours inside the inner surface are considered green screen. Colours outside the outer surface are opaque foreground. Colours between

1261-446: A field monitor, to the side of the screen, to see where they are putting their hands against the background images. A newer technique is to project a faint image onto the screen. 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 be composited together, which allows actors to be filmed separately and then placed together in

1358-425: A filter or the high contrast film's colour sensitivity to expose only blue (and higher) frequencies. Blue light only shines through the colour negative where there is not blue in the scene, so this left the film clear where the blue screen was, and opaque elsewhere, except it also produced clear for any white objects (since they also contained blue). Removing these spots could be done by a suitable double-exposure with

1455-454: A green screen and the Green Goblin had to be shot in front of a blue screen. The colour difference is because Spider-Man wears a costume which is red and blue in colour and the Green Goblin wears a costume which is entirely green in colour. If both were shot in front of the same screen, parts of one character would be erased from the shot. For a clean division of foreground from background, it

1552-509: A green top to make it appear that the subject has no body), because the clothing may be replaced with the background image/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

1649-531: A lower bit rate. There are thousands of audio and video codecs, ranging in cost from free to hundreds of dollars or more. This variety of codecs can create compatibility and obsolescence issues. The impact is lessened for older formats, for which free or nearly-free codecs have existed for a long time. The older formats are often ill-suited to modern applications, however, such as playback on small portable devices. For example, raw uncompressed PCM audio (44.1 kHz, 16-bit stereo, as represented on an audio CD or in

1746-433: A narrow frequency band, which can then be separated from the other light using a prism, and projected onto a separate but synchronized film carrier within the camera. This second film is high-contrast black and white, and is processed to produce the matte. 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

1843-420: A quarter of the time needed for other methods. In principle, any type of still background can be used as a chroma key instead of a solid colour. First the background is captured without actors or other foreground elements; then the scene is recorded. The image of the background is used to cancel the background in the actual footage; for example in a digital image, each pixel will have a different chroma key. This

1940-463: A reasonable match. For outdoor scenes, overcast days create a diffuse, evenly coloured light which can be easier to match in the studio, whereas direct sunlight needs to be matched in both direction and overall colour based on time of day. A studio shot taken in front of a green screen will naturally have ambient light the same colour as the screen, due to its light scattering. This effect is known as spill . This can look unnatural or cause portions of

2037-476: A scene featuring a genie escaping from a bottle was the first use of a proper bluescreen process to create a travelling matte for The Thief of Bagdad (1940), which won the Academy Award for Best Special Effects that year. In 1950, Warner Brothers employee and ex- Kodak researcher Arthur Widmer began working on an ultraviolet travelling matte process. He also began developing bluescreen techniques: one of

SECTION 20

#1732863135436

2134-440: A technological perspective it was equally possible to use the blue or green channel, but because blue clothing was an ongoing challenge, the green screen came into common use. Newscasters sometimes forget the chroma key dress code, and when the key is applied to clothing of the same colour as the background, the person would seem to disappear into the key. Because green clothing is less common than blue, it soon became apparent that it

2231-560: A tendency to reduce the need for lossy codecs for some media. Many popular codecs are lossy. They reduce quality in order to maximize compression. Often, this type of compression is virtually indistinguishable from the original uncompressed sound or images, depending on the codec and the settings used. The most widely used lossy data compression technique in digital media is based on the discrete cosine transform (DCT), used in compression standards such as JPEG images, H.26x and MPEG video, and MP3 and AAC audio. Smaller data sets ease

2328-407: A white backdrop to include human actors with cartoon characters and backgrounds in his Alice Comedies . The blue screen method was developed in the 1930s at RKO Radio Pictures . At RKO, Linwood Dunn used an early version of the travelling matte to create "wipes" – where there were transitions like a windshield wiper in films such as Flying Down to Rio (1933). Credited to Larry Butler ,

2425-503: Is 320x240 video, except for the Sony DCR-PC1000 camcorder and some Panasonic camcorders that provide transfer of a full-quality DV stream via USB by using the UVC protocol. Full-quality DV can also be captured via USB or Thunderbolt by using separate hardware that receives DV data from the camcorder over a FireWire cable and forwards it without any transcoding to the computer via a USB cable or

2522-440: Is 50% wider compared to baseline. Accordingly, tape is transported 50% faster, which reduces recording time by one third compared to regular DV. Because of the wider track and track pitch, DVCAM has the ability to do a frame-accurate insert edit, while regular DV may vary by a few frames on each edit compared to the preview. Digital8 is a combination of the tape transport originally designed for analog Video8 and Hi8 formats with

2619-551: Is a high-definition video format that can be thought of as four DV codecs that work in parallel. Video data rate depends on frame rate and can be as low as 40 Mbit/s for 24 frame/s mode and as high as 100 Mbit/s for 50/60 frame/s modes. Like DVCPRO50, DVCPRO HD employs 4:2:2 color sampling. It was introduced in 2000. DVCPRO HD uses smaller raster size than broadcast high definition television: 960x720 pixels for 720p, 1280x1080 for 1080/59.94i and 1440x1080 for 1080/50i. Similar horizontal downsampling (using rectangular pixels )

2716-419: Is a variation of DV developed by Panasonic and introduced in 1995, originally intended for use in electronic news gathering (ENG) equipment. Unlike baseline DV, DVCPRO uses locked audio , meaning the audio sample clock runs in sync with the video sample clock. Audio is available in 16-bit/48 kHz precision. When recorded to tape, DVCPRO uses wider track pitch—18 μm vs. 10 μm of baseline DV—which reduces

2813-405: Is achieved by a simple numerical comparison between the video and the pre-selected colour. If the colour 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. In order to create an illusion that characters and objects filmed are present in the intended background scene, the lighting in the two scenes must be

2910-451: Is also important that clothing and hair in the foreground shot have a fairly simple silhouette, as fine details such as frizzy hair may not resolve properly. Similarly, partially transparent elements of the costume cause problems. Blue was originally used for the film industry as making the separations required a film that would only respond to the screen colour, and film that responded only to blue and higher frequencies (ultraviolet, etc.)

3007-409: Is being compressed and uses it as a disguise. This disguise appears as a codec download through a pop-up alert or ad. When a user goes to click or download that codec, the malware is then installed on the computer. Once a fake codec is installed it is often used to access private data, corrupt an entire computer system or to keep spreading the malware. One of the previous most used ways to spread malware

DV (video format) - Misplaced Pages Continue

3104-496: Is best to have as narrow a colour range as possible being replaced. A shadow would present itself as a darker colour 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 or scenes reshot. 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

3201-461: Is especially true if the data is to undergo further processing (for example, editing ) in which case the repeated application of processing (encoding and decoding) on lossy codecs will degrade the quality of the resulting data such that it is no longer identifiable (visually, audibly, or both). Using more than one codec or encoding scheme successively can also degrade quality significantly. The decreasing cost of storage capacity and network bandwidth has

3298-405: Is formed from either 10 or 12 such sequences, depending on scanning rate, which results in a data rate of about 25 Mbit/s for video, and an additional 1.5 Mbit/s for audio. When written to tape, each sequence corresponds to one complete track. Baseline DV employs unlocked audio . This means that the sound may be +/- ⅓ frame out of sync with the video. However, this is the maximum drift of

3395-441: Is not an ISO standard . There are also other well-known container formats, such as Ogg , ASF , QuickTime , RealMedia , Matroska , and DivX Media Format . MPEG transport stream , MPEG program stream , MP4 , and ISO base media file format are examples of container formats that are ISO standardized. Fake codecs are used when an online user takes a type of codec and installs viruses and other malware into whatever data

3492-409: Is some use of the specific full-intensity magenta colour #FF00FF in digital colour images to encode (1-bit) transparency; this is sometimes referred to as "magic pink". This is not a photographic technique and the extraction of the foreground from the background is trivial. The biggest challenge when setting up a blue screen or green screen is even lighting and the avoidance of shadow because it

3589-437: Is sometimes referred to as a difference matte . However, this makes it easy for objects to be accidentally removed if they happen to be similar to the background, or for the background to remain due to camera noise or if it happens to change slightly from the reference footage. A background with a repeating pattern alleviates many of these issues, and can be less sensitive to wardrobe colour than solid-colour backdrops. There

3686-496: Is used in many other magnetic tape-based HD formats such as HDCAM . To maintain compatibility with HD-SDI , DVCPRO100 equipment upsamples video during playback. Variable framerates (from 4 to 60 frame/s) are available on Varicam camcorders. DVCPRO HD equipment offers backward compatibility with older DV/DVCPRO formats. When recorded to tape in standard-play mode, DVCPRO HD uses the same 18 μm track pitch as other DVCPRO flavors. A long play variant, DVCPRO HD-LP, doubles

3783-412: Is used. Cassettes labeled as DVCPRO HD have a red tape door and indicate recording time when DVCPRO HD-LP format is used; a second number may be used for DVCPRO HD recording, which will be half as long. Panasonic stipulated use of a particular magnetic-tape formulation— metal particle (MP)—as an inherent part of its DVCPRO family of formats. Regular DV tape uses Metal Evaporate (ME) formulation (which, as

3880-520: Is usually a two-way port, so that DV video data can be output to a computer (DV-out), or input from either a computer or another camcorder (DV-in). The DV-in capability makes it possible to copy edited DV video from a computer back onto tape, or make a lossless copy between two mutually connected DV camcorders. However, models made for sale in the European Union usually had the DV-in capability disabled in

3977-455: The BBC ), or by various terms for specific colour-related variants such as green screen or blue screen ; chroma keying can be done with backgrounds of any colour that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from any human skin colour . No part of the subject being filmed or photographed may duplicate the colour used as

DV (video format) - Misplaced Pages Continue

4074-407: The focal length of the lenses used can affect the success of chroma key. Another challenge for blue screen or green screen is proper camera exposure . Underexposing or overexposing a coloured backdrop can lead to poor saturation levels. In the case of video cameras, underexposed images can contain high amounts of noise , as well. The background must be bright enough to allow the camera to create

4171-440: The 2010s, DV rapidly grew obsolete as cameras using memory cards and solid-state drives became the norm, recording at higher bitrates and resolutions that were impractical for mechanical tape formats. Additionally, as manufacturers switched from interlaced to superior progressive recording methods, they broke the interoperability that had previously been maintained across multiple generations of DV and HDV equipment. DV

4268-690: The 63-minute ones and Panasonic advised against playing these cassettes in DVCPRO decks. Medium or M-size cassettes (97.5 × 64.5 × 14.6 mm), which are about the size of eight-millimeter cassettes, are used in professional Panasonic equipment and are often called DVCPRO tapes . Panasonic video recorders that accept medium cassette can play back from and record to medium cassette in different flavors of DVCPRO format; they will also play small cassettes containing DV or DVCAM recording via an adapter. These cassettes come in lengths up to 66 minutes for DVCPRO, 33 minutes for DVCPRO50 and DVCPRO HD-LP, and 16.5 minutes for

4365-871: The DCT compression stage, chroma subsampling is applied to the source video in order to reduce the amount of data to be compressed. Baseline DV uses 4:1:1 subsampling in its 60 Hz variant and 4:2:0 subsampling in the 50 Hz variant. Low chroma resolution of DV (compared to higher-end digital video formats) is a reason this format is sometimes avoided in chroma keying applications, though advances in chroma keying techniques and software have made producing quality keys from DV material possible. Audio can be stored in either of two forms: 16-bit Linear PCM stereo at 48 kHz sampling rate (768 kbit/s per channel, 1.5 Mbit/s stereo), or four nonlinear 12-bit PCM channels at 32 kHz sampling rate (384 kbit/s per channel, 1.5 Mbit/s for four channels). In addition,

4462-517: The DV codec . Digital8 equipment records in DV format only, but usually can play back Video8 and Hi8 tapes as well. The table below show the physical DV cassette formats at a glance: DV was originally designed for recording onto magnetic tape . Tape is enclosed into videocassette of four different sizes: small, medium, large and extra-large. All DV cassettes use 1 ⁄ 4 inch (6.4 mm) wide tape. DV on magnetic tape uses helical scan , which wraps

4559-609: The DV specification also supports 16-bit audio at 44.1 kHz (706 kbit/s per channel, 1.4 Mbit/s stereo), the same sampling rate used for CD audio. In practice, the 48 kHz stereo mode is used almost exclusively. The audio, video, and metadata are packaged into 80-byte Digital Interface Format (DIF) blocks which are multiplexed into a 150-block sequence. DIF blocks are the basic units of DV streams and can be stored as computer files in raw form or wrapped in such file formats as Audio Video Interleave (AVI), QuickTime (QT) and Material Exchange Format (MXF). One video frame

4656-483: The VHS and Digital8 formats that use thinner tape for their longest-length variants, the 276-minute DV cassette employs the same tape as its shorter-length variants. On the DVCPRO side, these cassettes have nearly double the tape capacity of their M-size counterparts, with duration up to 126 minutes for DVCPRO, 63 minutes for DVCPRO50 and DVCPRO HD-LP, and 31.5 minutes for the original DVCPRO HD. A thin-tape 184/92/46-minute version

4753-405: The actor in front of a blue screen together with the background footage, one frame at a time. In the early 1970s, American and British television networks began using green backdrops instead of blue for their newscasts. During the 1980s, minicomputers were used to control the optical printer. For the film The Empire Strikes Back , Richard Edlund created a "quad optical printer" that accelerated

4850-603: The audio/video synchronization; it is not compounded throughout the recording. Sony and Panasonic created their proprietary versions of DV aimed toward professional & broadcast users, which use the same compression scheme, but improve on robustness, linear editing capabilities, color rendition and raster size. All DV variants except for DVCPRO Progressive are recorded to tape within interlaced video stream. Film-like frame rates are possible by using pulldown . DVCPRO HD supports native progressive format when recorded to P2 memory cards. DVCPRO, also known as DVCPRO25 and D-7,

4947-449: 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 in the 1990s of practical blue LEDs, which also allow for emerald green LEDs. There is also a form of colour keying that uses light spectrum invisible to human eye. Called Thermo-Key, it uses infrared as

SECTION 50

#1732863135436

5044-445: The background video. Chroma keying is also common in the entertainment industry for visual effects in movies and video games. Rotoscopy may instead be carried out on subjects that are not in front of a green (or blue) screen. Motion tracking can also be used in conjunction with chroma keying, such as to move the background as the subject moves. Prior to the introduction of travelling mattes and optical printing , double exposure

5141-459: The backing, or the part may be erroneously identified as part of the backing. It is commonly used for live weather forecast broadcasts in which a news presenter is seen standing in front of a large CGI map which is really a large blue or green background. Using a blue screen, different weather maps are added on the parts of the image in which the colour is blue. If the news presenter wears blue clothes, their clothes will also be replaced with

5238-478: The camera being more sensitive to green light. In analog television , colour 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 pre-selected colour. In-phase portions of the video are replaced by the alternate background video. In digital colour TV , colour is represented by three numbers (red, green, blue intensity levels). Chroma key

5335-452: The camera is always in motion. The principal subject is filmed or photographed against a background consisting of a single colour or a relatively narrow range of colours, usually blue or green because these colours are considered to be the furthest away from skin tone. The portions of the video which match the pre-selected colour are replaced by the alternate background video. This process is commonly known as " keying ", "keying out" or simply

5432-443: The chance of dropout errors during recording. Two extra longitudinal tracks provide support for audio cue and for timecode control. Tape is transported 80% faster compared to baseline DV, resulting in shorter recording time. Long Play mode is not available. DVCPRO50 was introduced by Panasonic in 1997 and is often described as two DV codecs working in parallel. The DVCPRO50 doubles the coded video data rate to 50 Mbit/s. This has

5529-454: The characters to disappear, so must be compensated for, or avoided by using a larger screen placed far from the actors. The depth of field used to record the scene in front of the coloured screen should match that of the background. This can mean recording the actors with a larger depth of field than normal. A chroma key subject must avoid wearing clothes which are similar in colour to the chroma key colour(s) (unless intentional e.g., wearing

5626-445: The cleanest key. In the digital television and cinema age, much of the tweaking that was required to make a good quality key has been automated. However, the one constant that remains is some level of colour coordination to keep foreground subjects from being keyed out. Before electronic chroma keying, compositing was done on (chemical) film. The camera colour negative was printed onto high-contrast black and white negative, using either

5723-409: The colour positive (thus turning any area containing red or green opaque), and many other techniques. The result was film that was clear where the blue screen was, and opaque everywhere else. This is called a female matte , similar to an alpha matte in digital keying. Copying this film onto another high-contrast negative produced the opposite male matte . The background negative was then packed with

5820-440: The data to reduce transmission bandwidth or storage space. Compression codecs are classified primarily into lossy codecs and lossless codecs. Lossless codecs are often used for archiving data in compressed form while retaining all information present in the original stream. If preserving the original quality of the stream is more important than eliminating the correspondingly larger data sizes, lossless codecs are preferred. This

5917-537: The digital signals back to analog form using an audio decoder for playback. An example of this is the codecs used in the sound cards of personal computers. A video codec accomplishes the same task for video signals. When implementing the Infrared Data Association (IrDA) protocol, an endec may be used between the UART and the optoelectronic systems. In addition to encoding a signal, a codec may also compress

SECTION 60

#1732863135436

6014-582: The effect of cutting total record time of any given storage medium in half. Chroma resolution is improved by using 4:2:2 chroma subsampling. Following the introduction of the AJ-SDX900 camcorder in 2003, DVCPRO50 was used in many productions where high definition video was not required. For example, BBC used DVCPRO50 to record high-budget TV series, such as Space Race (2005) and Ancient Rome: The Rise and Fall of an Empire (2006). A similar format, D-9 (or Digital-S) , offered by JVC, uses videocassettes with

6111-433: The female matte and exposed onto a final strip of film, then the camera negative was packed with the male matte and was double-printed onto this same film. These two images combined creates the final effect. The most important factor for a key is the colour separation of the foreground (the subject) and background (the screen) – a blue screen will be used if the subject is predominantly green (for example plants), despite

6208-474: The firmware by the manufacturer because the camcorder would be classified by the EU as a video recorder and would therefore attract higher duty; a model which only had DV-out could be sold at a lower price in the EU. When video is captured onto a computer it is stored in a container file, which can be either raw DV stream, AVI, WMV or QuickTime. Whichever container is used, the video itself is not re-encoded and represents

6305-503: 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 name "Chroma-Key" was RCA 's trade name for the process, as used on its NBC television broadcasts, incorporating patents granted to RCA's Albert N. Goldsmith. A very early broadcast use was NBC's George Gobel Show in fall 1957. Petro Vlahos

6402-427: The green channel. Green can also be used outdoors where the light colour temperature is significantly blue. Red is avoided as it is in human skin, and any other colour is a mix of primaries and thus produces a less clean extraction. A so-called " yellow screen " is accomplished with a white backdrop. Ordinary stage lighting is used in combination with a bright yellow sodium lamp. The sodium light falls almost entirely in

6499-414: The green screen two stops higher than the subject, or vice versa. Sometimes a shadow can be used to create a visual effect. Areas of the blue screen or green screen with a shadow on them can be replaced with a darker version of the desired background video image, making it look like the person is casting a shadow on them. Any spill of the chroma key colour will make the result look unnatural. A difference in

6596-423: The key colour, which would not be replaced by background image during postprocessing . For Star Trek: The Next Generation , an ultraviolet light matting process was proposed by Don Lee of CIS Hollywood 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

6693-412: The label posted. Cassettes labeled as DV indicate recording time of baseline DV; another number can indicate recording time of Long Play DV. Cassettes labeled as DVCPRO have a yellow tape door and indicate recording time when DVCPRO25 is used; with DVCPRO50 the recording time is half, with DVCPRO HD it is a quarter. Cassettes labeled as DVCPRO50 have a blue tape door and indicate recording time when DVCPRO50

6790-496: The late 1990s and early 2000s, DV was strongly associated with the transition from analog to digital desktop video production, and also with several enduring " prosumer " camera designs such as the Sony VX-1000 . In 2003, DV was joined by a successor format called HDV , which used the same tapes but with an updated video codec with high-definition video ; HDV cameras could typically switch between DV and HDV recording modes. In

6887-409: 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 colour range. In order to get the cleanest key from shooting green screen, it is necessary to create a value difference between the subject and the green screen. In order to differentiate the subject from the screen, a two-stop difference can be used, either by making

6984-506: The luminance sampling frequency of 13.5 MHz. This results in 480 scanlines per complete frame for the 60 Hz system, and 576 scanlines per complete frame for the 50 Hz system. In both systems the active area contains 720 pixels per scanline, with 704 pixels used for content and 16 pixels on the sides left for digital blanking. The same frame size is used for 4:3 and 16:9 frame aspect ratios, resulting in different pixel aspect ratios for fullscreen and widescreen video. Prior to

7081-474: The media to be encoded. For example, a digital video (using a DV codec) of a sports event needs to encode motion well but not necessarily exact colors, while a video of an art exhibit needs to encode color and surface texture well. Audio codecs for cell phones need to have very low latency between source encoding and playback. In contrast, audio codecs for recording or broadcasting can use high-latency audio compression techniques to achieve higher fidelity at

7178-408: The multimedia data streams to be useful in stored or transmitted form, they must be encapsulated together in a container format . Lower bitrate codecs allow more users, but they also have more distortion. Beyond the initial increase in distortion, lower bit rate codecs also achieve their lower bit rates by using more complex algorithms that make certain assumptions, such as those about the media and

7275-1140: The name suggests, uses physical vapor deposition to deposit metal onto the tape), which was pioneered for use in Hi8 camcorders. Early Hi8 ME tapes were plagued with excessive dropouts, which forced many shooters to switch to more expensive MP tapes. After the technology improved, the dropout rate was greatly reduced, nevertheless Panasonic deemed ME formulation not robust enough for professional use. Tape-based professional Panasonic DVCPRO camcorders and decks only record onto DVCPRO-branded cassettes, effectively preventing use of ME tape. Small cassettes (66 x 48 x 12.2 mm), also known as S-size or MiniDV cassettes, had been intended for amateur use, but have become accepted in professional productions as well. MiniDV cassettes are used for recording baseline DV, DVCAM, and HDV . These cassettes come in lengths up to about 14~20.8 GB for 63 or 90 minutes of DV or HDV video. When recording in DVCAM, these cassettes hold up to 41 minutes of video. There are some 83-minute versions but these use thinner tape than

7372-584: The original DVCPRO HD. Large or L-size cassettes (125.1 x 78 x 14.6 mm) are close in size to small MII cassettes and are accepted by most standalone DV tape recorders and are used in many shoulder-mount camcorders. The L-size cassette can be used in both Sony and Panasonic equipment; nevertheless, they are often called DVCAM tapes . Older Sony decks would not play large cassettes with DVCPRO recordings, but newer models can play these and M-size DVCPRO cassettes. These cassettes come in lengths up to 276 minutes of DV or HDV video (or 184 minutes for DVCAM). Unlike

7469-538: The packet loss rate. Other codecs may not make those same assumptions. When a user with a low bitrate codec talks to a user with another codec, additional distortion is introduced by each transcoding . Audio Video Interleave (AVI) is sometimes erroneously described as a codec, but AVI is actually a container format, while a codec is a software or hardware tool that encodes or decodes audio or video into or from some audio or video format. Audio and video encoded with many codecs might be put into an AVI container, although AVI

7566-439: The pixel is fully in the foreground object, and intermediate values indicate the pixel is partially covered by the foreground object (or it is transparent). A further function g ( r ,  g ,  b ) → ( r ,  g ,  b ) is needed to remove green spill on the foreground objects. A very simple f () function for green screen is A ( r + b ) − Bg where A and B are user adjustable constants with

7663-462: The process considerably and saved money. He received a special Academy Award for his innovation. For decades, travelling 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. Meteorologists on television often use

7760-546: The recording density by using 9 μm track pitch. DVCPRO HD is codified as SMPTE 370M; the DVCPRO ;HD tape format is SMPTE 371M, and the MXF Op-Atom format used for DVCPRO HD on P2 cards is SMPTE 390M. While technically DVCPRO HD is a direct descendant of DV, it is used almost exclusively by professionals. Tape-based DVCPRO HD cameras exist only in shoulder mount variant. A similar format, Digital-S (D-9 HD),

7857-415: The same form-factor as VHS . Comparable high quality standard definition digital tape formats include Sony's Digital Betacam , introduced in 1993, and MPEG IMX , introduced in 2000. DVCPRO Progressive was introduced by Panasonic alongside DVCPRO50. It offered 480 or 576 lines of progressive scan recording with 4:2:0 chroma subsampling and four 16-bit 48 kHz PCM audio channels. Like HDV-SD , it

7954-441: The same scene. Chroma key allows performers to appear to be in any location without leaving the studio. Advances in computer technology have simplified the incorporation of motion into composited shots, even when using handheld cameras. Reference points such as a painted grid, X's marked with tape, or equally spaced tennis balls attached to the wall, can be placed onto the coloured background to serve as markers. In post-production,

8051-521: The specifics of video systems supporting 525-60 for NTSC and 625-50 for PAL . The IEC standards are available as publications sold by IEC and ANSI . DV uses lossy compression of video while audio is stored uncompressed. An intraframe video compression scheme is used to compress video on a frame-by-frame basis with the discrete cosine transform (DCT). Closely following the ITU-R Rec. 601 standard, DV video employs interlaced scanning with

8148-452: The strain on relatively expensive storage sub-systems such as non-volatile memory and hard disk , as well as write-once-read-many formats such as CD-ROM , DVD , and Blu-ray Disc . Lower data rates also reduce cost and improve performance when the data is transmitted, e.g., over the internet. Two principal techniques are used in codecs, pulse-code modulation and delta modulation . Codecs are often designed to emphasize certain aspects of

8245-409: The surfaces are partially covered, they are more opaque the closer they are to the outer surface. Sometimes more closed surfaces are used to determine how to remove green spill. It is also very common for f () to depend on more than just the current pixel's colour, it may also use the ( x ,  y ) position, the values of nearby pixels, the value from reference images or a statistical colour model of

8342-494: The tape around a tilted, rotating head drum with video heads mounted to it. As the drum rotates, the heads read the tape diagonally. DV, DVCAM and DVCPRO use a 21.7 mm diameter head drum at 9000 rpm. The diagonal video tracks read by the heads are 10 microns wide in DV tapes. Technically, any DV cassette can record any variant of DV video. Nevertheless, manufacturers often label cassettes with DV, DVCAM, DVCPRO, DVCPRO50 or DVCPRO HD and indicate recording time with regards to

8439-423: The window areas. In order to have figures in one exposure actually move in front of a substituted background in the other, a travelling matte was needed, to occlude the correct portion of the background in each frame. In 1918 Frank Williams patented a travelling matte technique, again based on using a black background. This was used in many films, such as The Invisible Man . In the 1920s, Walt Disney used

8536-467: Was also released. Extra-large cassettes or XL-size (172 x 102 x 14.6 mm) are close in size to VHS cassettes and have been designed for use in Panasonic equipment and are sometimes called DVCPRO XL. These cassettes are not widespread, only a few models of Panasonic tape recorders can accept them. Each XL-size cassette holds nearly double the amount of tape as the full-length L-size cassettes with

8633-410: Was awarded an Academy Award for his refinement of these techniques in 1964. His technique exploits the fact that most objects in real-world scenes have a colour whose blue-colour component is similar in intensity to their green-colour component. Zbigniew Rybczyński also contributed to bluescreen technology. An optical printer with two projectors, a film camera and a "beam splitter", was used to combine

8730-479: Was designed to be a standard for home video using digital data instead of analog . Compared to the analog Video8/Hi8 , VHS-C and VHS formats, DV features a higher video resolution (on par with professional-grade Digital Betacam ) and also records audio digitally at 16-bit like CD . The most popular tape format using a DV codec was MiniDV ; these cassettes measured just 6.35 mm/¼ inch, making it ideal for video cameras and rendering older analog formats obsolete. In

8827-612: Was developed by the HD Digital VCR Association: in April 1994, 55 companies worldwide took part, which developed the standards and specifications of the format. The original DV specification, known as Blue Book , was standardized within the IEC  61834 family of standards. These standards define common features such as physical videocassettes , recording modulation method, magnetization, and basic system data in part 1. Part 2 describes

8924-427: Was easier to use a green matte screen than it was to constantly police the clothing choices of on-air talent. Also, because the human eye is more sensitive to green wavelengths, which lie in the middle of the visible light spectrum, the green analog video channel typically carried more signal strength, giving a better signal to noise ratio compared to the other component video channels, so green screen keys could produce

9021-583: Was fake AV pages and with the rise of codec technology, both have been used in combination to take advantage of online users. This combination allows fake codecs to be automatically downloaded to a device through a website linked in a pop-up ad, virus/codec alerts or articles as well. Chroma key Chroma key compositing , or chroma keying , is a visual-effects and post-production technique for compositing (layering) two or more images or video streams together based on colour hues ( chroma range). The technique has been used in many fields to remove

9118-507: Was far easier to manufacture and make reliable than film that somehow excluded both frequencies higher and lower than the screen colour. In television and digital film making, however, it is equally easy to extract any colour, and green quickly became the favoured colour. Bright green is less likely to be in the foreground objects, colour film emulsions usually had much finer grain in the green, and lossy compression used for analog video signals and digital images and movies retain more detail in

9215-469: Was meant as an intermediate format during the transition time from standard definition to high definition video. The format offered six modes for recording and playback: 16:9 progressive (50 Mbit/s), 4:3 progressive (50 Mbit/s), 16:9 interlaced (50 Mbit/s), 4:3 interlaced (50 Mbit/s), 16:9 interlaced (25 Mbit/s), 4:3 interlaced (25 Mbit/s). The format was superseded by DVCPRO HD. DVCPRO HD, also known as DVCPRO100 and D-12,

9312-492: Was offered by JVC and used videocassettes with the same form-factor as VHS . The main competitor to DVCPRO HD was HDCAM , offered by Sony. It uses a similar compression scheme but at higher bitrate. In 1996, Sony responded with its own professional version of DV called DVCAM. Like DVCPRO, DVCAM uses locked audio, which prevents audio synchronization drift that may happen on DV if several generations of copies are made. When recorded to tape, DVCAM uses 15 μm track pitch, which

9409-464: Was used to introduce elements into a scene which were not present in the initial exposure. This was done using black draping where a green screen would be used today. George Albert Smith first used this approach in 1898. In 1903, The Great Train Robbery by Edwin S. Porter used double exposure to add background scenes to windows which were black when filmed on set, using a garbage matte to expose only

#435564