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• Blanking Interval
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Analog television Structure of a video signal
1 The front porch is a brief (about 1.5 microsecond) period inserted between the end of each transmitted line of picture and
the leading edge of the next line sync pulse. Its purpose was to allow voltage levels to stabilise in older televisions, preventing
interference between picture lines. The front porch is the first component of the horizontal
blanking interval which also contains the horizontal sync pulse and the back porch.
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Analog television Vertical synchronization
1 Vertical synchronization (Also vertical sync or VSYNC) separates the video fields. In PAL and NTSC, the vertical sync pulse occurs within the vertical blanking interval. The vertical sync pulses are made by prolonging the
length of HSYNC pulses through almost the entire length of the scan
line.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Analog television Vertical synchronization
1 Software such as Video Games and computer aided design (CAD) packages often allow vertical synchronization as an option,
because it delays the image update until the vertical blanking interval
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Linux console - Control characters
1 The console also supports extended escape sequences, ANSI CSI Mode sequences, and DEC Private Mode
sequences. These extended sequences can control colors, visual effects like blinking,
underline, intensity and inverse video, bell tone frequency and duration, VESA screen blanking interval. Aside from the textual blanking, there is no known way to place
the VGA adapter into standby.
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Digital Video Broadcasting - Content
1 Older technologies such as teletext (DVB-TXT) and vertical blanking interval data (DVB-VBI) are also
supported by the standards to ease conversion. However, for many
applications more advanced alternatives like DVB-SUB for
subtitling are available.
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Seven-segment display - Implementations
1 To operate any particular segment of any digit, the controlling integrated circuit would turn on the cathode
driver for the selected digit, and the anode drivers for the desired segments; then after a short
blanking interval the next digit would be selected and new segments lit, in
a sequential fashionhttps://store.theartofservice.com/the-blanking-interval-toolkit.html
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Macintosh 128K - Processor and memory
1 The 68000 and video controller take turns accessing DRAM every four CPU cycles during display of the frame buffer, while the 68000
has unrestricted access to DRAM during vertical and horizontal blanking intervals. Such an
arrangement reduces the overall performance of the CPU as much as 35% for most codes as the display logic often blocks the CPU's access to RAM. This made the machine appear to run slower than several of its competitors, despite
the nominally high clock rate.
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Electronic program guide - Current applications
1 Older television IPGs like Guide Plus+ relied on analog technology (such as
the vertical blanking interval of analog television video signals) to
distribute listings data to IPG-enabled consumer receiving equipment
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HDMI 1.4 - TMDS
1 During the Data Island period (which occurs during the horizontal and vertical blanking intervals), audio and auxiliary data are transmitted
within a series of packets
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Composite video - Extensions to the composite video standard
1 Since TV screens hide the vertical blanking interval of a composite video signal and even
overscan|crop the edges of the picture, extensions have been implemented by taking advantage of these unseen parts of the signal. Examples of these extensions include teletext, closed captioning, digital information regarding the show title, transmitting a set of reference
colors that allows TV sets to automatically correct the hue mal-adjustments common with
the NTSC color encoding system, etc.
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Atari 2600 - Hardware
1 After the controller scanned the last active line, a more leisurely vertical
blanking interval began, during which the game could process input and update the positions and states
of objects in the world
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Digital Millennium Copyright Act - Effect on analog video equipment
1 The technology works by adding additional lines to the video signal. In the NTSC video standard, blank lines (vertical blanking intervals) that the
user cannot see are used for functions like closed captioning. Rovi Corporation uses these blank lines to
implement its ACP technology.
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Digital Visual Interface - Technical overview
1 In single-link mode, the maximum pixel clock frequency is 165MHz that supports a maximum resolution of 2.75megapixels (including blanking
interval) at 60Hz refresh
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Type A videotape
1 The VPR-1 had several problems, it did not record the vertical blanking interval, which is why it was not compliant to FCC broadcast standards. The video quality
was not as good as other broadcast VTRs. Thus Sony and Ampex agreed to make a SMPTE approved type Type C videotape|C format VTR (which was based on Type A). Hitachi also later made a C format VTR.
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D-1 (Sony) - Format
1 Ancillary data can be put in H/V
blanking intervals
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LaserDisc - Advantages
1 The vertical blanking interval, where the Macrovision signal would be
implemented, was also used for the internal timing on LaserDisc players, so test discs with Macrovision would
not play at all
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Video - Analog television
1 An analog video format consists of more information than the visible content of the frame. Preceding and following the image
are lines and pixels containing synchronization information or a time
delay. This surrounding margin is known as a 'blanking interval' or 'blanking
region'; the horizontal and vertical front porch and back porch are the building
blocks of the blanking interval.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Kinescope - Technology
1 The time taken physically to move the film on by one frame and stop it so that the gate can be opened to expose a new frame of film to the two field (video)|fields of television
picture is much longer than the vertical blanking interval between
these fields—so the film is still moving when the start of the next
field is being displayed on the television screenhttps://store.theartofservice.com/the-blanking-interval-toolkit.html
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D-3 (video)
1 Four channels of 48 kHz 16-20 bit PCM audio, and other ancillary data,
are inserted during the vertical blanking interval
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Dynamic random-access memory - Refresh rate
1 A few real-time systems refresh a portion of memory at a time
determined by an external timer function that governs the operation of the rest of a system, such as the
vertical blanking interval that occurs every 10–20ms in video equipment
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NTSC - Lines and refresh rate
1 This blanking interval was originally designed to simply blank the
receiver's CRT to allow for the simple analog circuits and slow vertical
retrace of early TV receivers
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Display Serial Interface
1 When in HS mode, commands are transmitted during the vertical blanking
interval.
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Broadcast television systems - Viewing technology
1 For this reason, it is necessary to shut off the electron beam
(corresponding to a video signal of zero luminance) during the time it
takes to reorient the beam from the end of one line to the beginning of the next (horizontal retrace) and
from the bottom of the screen to the top (vertical retrace or vertical
blanking interval)https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Framebuffer - Page flipping
1 This switch is usually done during the vertical blanking interval to prevent
the screen from Screen tearing|tearing (i.e., half the old frame is shown, and half the new frame is
shown).
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Teletext
1 Teletext is a means of sending text and diagrams to a properly equipped television screen by use of
one of the vertical blanking interval lines that together form the dark band dividing pictures
horizontally on the television screen.[http://news.google.com/newspapers?
nid=950dat=19790516id=DwEMAAAAIBAJsjid=21gDAAAAIBAJpg=6334,14832 Teletext: Soon You'll
Be Punching Buttons And Talking Back To Your TV] It offers a range of text-based information, typically including news, weather and TV
scheduleshttps://store.theartofservice.com/the-blanking-interval-toolkit.html
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Teletext - Invention Design
1 His configuration contained all the fundamental elements of classic
Teletext including 24 text rows of 40 characters each, page selection,
multiple screens of information and vertical blanking interval data
transmission
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Teletext - Technology
1 Teletext information is broadcast in the vertical blanking interval between image frames in a broadcast television signal
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Teletext - Data transmission
1 Teletext in the PAL B system can make use the Vertical Blanking Interval|VBI lines 6–22 in first half
image and 318–334 in the other to transmit 360 data bits including clock run-in and framing code during the PAL#PAL signal details|active video period at a rate of using binary Non-return-to-zero|NRZ line
coding.[ http://www.ee-techs.com/tv/teletext-fullerton.pdf ee-techs.com – What is Teletext?],
2004ETS 300 706 – Enhanced Teletext specification, May 1997 The amplitude for a 0 is black level ±2% and a 1 is 66±6% of the difference between black
and peak white level
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Teletext - Data transmission
1 In the case of the Ceefax and ORACLE systems and their successors in the UK, the teletext signal is transmitted as part of the ordinary analogue TV signal but concealed from view in the Vertical Blanking Interval (VBI) television lines which do not carry
picture information. The teletext signal is digitally coded as 45-byte packets, so the resulting rate is 7,175 bits per second per
used lines (41 7-bit 'bytes' per line, on each of 25 frames per second).
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Teletext - Video Program System
1 Like teletext, this signal is also broadcast in the vertical blanking interval
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Teletext - Digital teletext
1 This emulation is only possible due to the DVB-TXT and DVB-VBI sub-
standards of Digital Video Broadcasting|DVB, which allow a set-
top box or integrated DVB TV to reproduce the vertical blanking interval data in which Teletext is
carried.
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576i
1 In analogue Vertical blanking interval|49 additional lines without
image content are added to the displayed frame of 576 lines to allow time for older CRT circuits to retrace
for the next frame,The 625-line television standard was introduced in
the early 1950s
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Windows 98 - Windows Driver Model
1 TV listings could be updated from the Internet and WaveTop Data
Broadcasting allowed extra data about broadcasts to be received via regular television signals using an
antenna or cable, by embedding data streams into the vertical blanking interval (VBI) portion of existing
broadcast television signals.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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TBS (TV channel) - Other programming
1 Throughout the 1980s and the early 1990s, TBS also carried the Electra (teletext)|Electra teletext service on its vertical blanking interval; Electra was discontinued in 1993 due to a
lack of funding
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Atari BASIC - Hardware support
1 A dedicated graphics microprocessor, ANTIC, reads these out during the
horizontal blanking interval to determine how to display the next TV
line
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Atari BASIC - Interrupts
1 Short sections of machine language code can be executed during the
horizontal blanking interval, and this is typically done to change the values in the color registers,
horizontal sprite positions and so forth thus giving the appearance of more colors or more flexible sprites than the hardware provides ab initio
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Atari BASIC - Interrupts
1 During the vertical blanking interval, a much longer interval, another interrupt is generated and the
Operating System hooks into this to perform some housekeeping tasks
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NTSC - Lines and refresh rate
1 This blanking interval was originally designed to simply blank the
receiver's CRT to allow for the simple analog circuits and slow vertical
retrace of early TV receivers
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Babylon 5 - Mastering problems
1 After visiting Warner Bros., who were stretching the Horizontal blanking interval|horizontal interval for an episode of Lois Clark: The New
Adventures of Superman|Lois Clark, producer John Copeland convinced them to allow Babylon 5 to be shot on Super 35|Super 35mm film stock
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TBS (TV network) - Other programming
1 Throughout the 1980s and the early 1990s, TBS also carried the Electra (teletext)|Electra teletext service on its vertical blanking interval; Electra was discontinued in 1993 due to a
lack of funding
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Closed captioning - Television and video
1 For all types of NTSC programming, captions are encoded into EIA-608|
line 21 of the vertical blanking interval – a part of the TV picture
that sits just above the visible portion and is usually unseen
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Film frame - Video frames
1 Analog blanking intervals separated video frames in the same way that frame lines did
in film
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Ricoh 5A22 - Major features
1 * Circuitry for generating Non-maskable interrupts on Vertical blanking interval|V-
blank
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Ricoh 5A22 - Major features
1 ** Horizontal blanking interval|H-blank DMA, for transferring small
data sets at the end of each scanline outside of the active display period
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Station identification - Television
1 Another way a television station can transmit its legal identification is to
do it continuously by putting readable text in the vertical blanking interval. One station that identifies this way is City (TV network)|City
owned-and-operated station CKVU-DT in Vancouver, British Columbia,
Canada.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Rec. 601 - Signal format
1 The Rec. 601 signal can be regarded as if it is a digitally encoded analog component video signal, and thus the sampling includes data for the horizontal and vertical sync and
blanking intervals. Regardless of the frame rate, the luminance sampling frequency is 13.5MHz. The samples are uniformly Quantization (signal
processing)|quantized using 8 or 10 bit PCM codes in the YCbCr domain.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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625-line television system
1 In analogue Vertical blanking interval|49 additional lines without
image content are added to the displayed frame of 576 lines to allow
time for older cathode ray tube circuits to retrace for the next frame,The 625-line television
standard was introduced in the early 1950shttps://store.theartofservice.com/the-blanking-interval-toolkit.html
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Coordinated Video Timings
1 The parameters defined by standard include horizontal blanking and
vertical blanking intervals, Horizontal scan rate|horizontal
frequency and refresh rate|vertical frequency (collectively, pixel clock
rate or video signal bandwidth), and horizontal sync|horizontal/vertical
sync polarity.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Coordinated Video Timings - Reduced blanking
1 CVT also specifies a mode (CVT-R) which significantly reduces these
blanking intervals (to a period insufficient for CRT displays to work correctly) in the interests of saving
video signal bandwidth when modern displays such as LCD monitors are
being used, since such displays typically do not require these pauses
in the picture datahttps://store.theartofservice.com/the-blanking-interval-toolkit.html
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Coordinated Video Timings - Reduced blanking
1 In revision 1.2, released in 2013, a new RB2 mode has been added which further reduces blanking interval and allows for unlimited vertical refresh rates, 4K/5K/8K
resolutions, 0.001 MHz pixel clock precision, and 1000/1001 modifier for ATSC/NTSC video timing modes.
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NTSC - Vertical interval reference
1 The standard NTSC video image contains some lines (lines 1–21 of each field) that are
not visible (this is known as the Vertical Blanking Interval, or VBI); all are beyond the edge of the viewable image, but only lines 1–
9 are used for the vertical-sync and equalizing pulses. The remaining lines were
deliberately blanked in the original NTSC specification to provide time for the electron beam in CRT-based screens to return to the
top of the display.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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NTSC - Vertical interval reference
1 Early teletext applications also used vertical blanking interval lines 14–18 and 20, but teletext over NTSC was never widely adopted by viewers.
[http://experimentaltvcenter.org/history/tools/ttext.php3?id=16 Tools | The
History Project]
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Display controller
1 In any case, it's the VDC's responsibility to generate the timing of the necessary video signals, such
as the horizontal and vertical Component video sync|
synchronisation signals, and the Video formats|blanking interval
signal.
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Videotex - North America
1 Telidon was able to deliver service using the vertical blanking interval of
a TV signal or completely by telephone using a Bell 202 modem|
Bell 202 style (split baud rate 150/1200) modem
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Nagravision - Analog system
1 A smartcard security microcontroller (in a key-shaped package) decrypts data that is transmitted during the blanking intervals of the TV signal
and extracts the random seed value needed for controlling the random
number generation
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SMPTE timecode - SMPTE timecode media
1 #Vertical interval timecode, a.k.a. 'VITC' (pronounced vit-see): recorded
directly into the VBI (vertical blanking interval) of the video signal
on each frame of video. The advantage of VITC is that, since it is a part of the playback video, it can be
read when the tape is stationary.
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Raster scan - Scanning pattern
1 In fact, spikes do occur, both horizontally and vertically, and the corresponding horizontal blanking
interval and vertical blanking interval give the deflection currents settle time to retrace and settle to their
new value. This happens during the blanking interval.
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Automatic gain control - Audio/video
1 Most VCR circuits use the amplitude of the vertical blanking interval|
vertical blanking pulse to operate the AGC. Video copy control schemes such as Macrovision exploit this,
inserting spikes in the pulse which will be ignored by most television
sets, but cause a VCR's AGC to overcorrect and corrupt the
recording.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Genlock - Natlock and Icelock
1 Natlock is a picture source synchronizing system using audio tone signals to describe the timing discrepancies between composite video signals, whilst Icelock uses
digital information conveyed in the vertical blanking interval of a
composite video signal.
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Ghost-canceling reference
1 In the United States, the GCR signal is a chirp in frequency of the modulating signal from 0
Hz to 4.2 MHz, transmitted during the vertical blanking interval over one video line, shifted in phase by 180° once per frame, with this pattern inverted every four lines. Television
receivers generate their own local versions of this signal, and use the comparison between the local and remote signals to tune out any
ghost images on the screen.
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Extended Data Services
1 XDS uses the same line in the vertical blanking interval as closed
captioning (NTSC line 21), and shares the available second field (video)|
video field bandwidth with the closed captioning channels CC3 and CC4,
and with the text channels TXT3 and TXT4.
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Vertical blanking interval
1 The 'vertical blanking interval' ('VBI'), also known as the 'vertical interval' or 'VBLANK', is the time difference
between the last line of one frame or field of a raster graphics|raster
display, and the beginning of the first line of the next frame
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Vertical blanking interval
1 Modern CRT circuitry does not require such a long blanking interval, and
thin panel displays require none, but the standards were established when the delay was needed (and to allow
the continued use of older equipment)
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Vertical blanking interval
1 In analog television systems the vertical blanking interval can be used for datacasting (to carry digital data), since nothing sent during the VBI is
displayed on the screen; various test signals, vertical interval timecode|
time codes, closed captioning, teletext, CGMS-A copy-protection
indicators, and various data encoded by the Extended Data Services|XDS
protocol (e.g., the content ratings for V-chip use) and other digital data can
be sent during this time period
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Vertical blanking interval
1 In video game systems the vertical blanking pulses are extensively used to time the
plotting of new graphics/removal of old ones in order to avoid screen tearing, as they
occur at an accurately known frequency, and many systems up to the History of video
game consoles (fourth generation)|16-bit era featured games and other graphical
programs where drawing was conducted during the blanking interval for this reason
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Television encryption - Leitch Technology
1 There was also a version that encrypted the audio using a digital
audio stream in the horizontal blanking interval like the VCII
system. One US network used that for its affiliate feeds and would turn off the analog sub carriers on the
satellite feed.
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Television encryption - Nagravision analogue system
1 A smartcard security microcontroller (in a key-shaped package) decrypts data that is transmitted during the blanking intervals of the TV signal
and extracts the random seed value needed for controlling the random
number generation
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CGMS-A
1 'Copy Generation Management System - Analog' ('CGMS-A') is a copy
protection mechanism for analog signal|analog television signals. It
consists of a waveform inserted into the non-picture Vertical Blanking
Interval (VBI) of an analogue video signal. If a compatible recording
device (for example, a DVD recorder) detects this waveform, it may block
or restrict recording of the video content.
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VIT signals - Blanking in CVS
1 In a composite video signal (CVS) there are two types of blanking: Horizontal blanking interval|horizontal and Vertical blanking interval|vertical. Horizontal blanking is between lines and vertical blanking is
between fields (half frames). In a poorly tuned TV receiver the horizontal blanking can be
seen at the right or left of the image and the vertical blanking can be seen at the top or
bottom of the image. VIT signals are inserted in the vertical blanking.
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Video Encoded Invisible Light - Other uses
1 VEIL acts together with CGMS-A signal (broadcast flag) in the vertical blanking
interval, where it is used to encode the Rights Assertion Mark (RAM) signal. The CGMS-A can be stripped too easily from the analog signal, therefore the presence of RAM but absence of CGMS-A will tell the copy protection system to
deny the copy.http://www.extremedrm.com/article/How+Will+Veils+Technology+Plug+The+Analog+
Hole/164259_1.aspxhttps://store.theartofservice.com/the-blanking-interval-toolkit.html
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Analog TV - Structure of a video signal
1 The front porch is a brief (about 1.5 microsecond) period inserted between the end of each transmitted line of picture and
the leading edge of the next line sync pulse. Its purpose was to allow voltage levels to stabilise in older televisions, preventing
interference between picture lines. The front porch is the first component of the horizontal
blanking interval which also contains the horizontal sync pulse and the back porch.
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Multiple buffering - Page flipping
1 The page-flip is much faster than copying the data and can guarantee that tearing will not be seen as long
as the pages are switched over during the monitor's vertical blanking
interval—the blank period when no video data is being drawn. The
currently active and visible buffer is called the 'front buffer', while the
background page is called the back buffer.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Horizontal scan rate
1 CRT timings actually include some horizontal scans before the visible display, after it, and
during the travel from bottom to top (known as vertical back porch, vertical front porch, and
vertical sync width, respectively, and collectively known as Vertical blanking interval|vertical blank
time), so the horizontal scan rate does not directly correlate to visible display lines, unless the
unseen lines are also known, but it can still be used to approximate the display lines, as the total
blank time is usually a small but significant portion of the total lines.
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Horizontal scan rate - Example
1 *Taking Vertical blanking interval into account, it would actually draw
1024x1.05 lines for a full frame cycle
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Guide Plus - Technical overview
1 The original analog television|analog service uses the vertical blanking interval (VBI) of :wikt:host|host
television stations that datacast the service, similar to the manner that closed captioning and teletext are
broadcast
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Overscan - Datacasting
1 The simplest form of this is closed captioning and teletext, both sent in the vertical blanking interval (VBI)
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Overscan - 625 / 525 or 576 / 480
1 A portion of this interval available in analogue, known as the vertical
blanking interval, can be used for older forms of analogue datacasting such as Teletext services (like Ceefax
and subtitling in the UK). The equivalent service on Digital
television does not use this method and instead often uses MHEG-5|
MHEG.https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Atari 8-bit - Software-driven modes
1 It was also possible by using the Display List Interrupt facility to display far more than the usual number of sprites on the screen
during the vertical blanking interval, with more colours than available
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Nominal analogue blanking
1 It consists of a variable and arbitrary gap of black (or nearly black) pixels at the left and right sides, which correspond to the end and start of the horizontal blanking interval: the
Analog television#Structure of a video signal|front porch at the right side (the end of a line,
before the sync pulse), and the Analog television#Structure of a video signal|back
porch at the left side (the start of a line, after the sync pulse and before drawing the next
line)https://store.theartofservice.com/the-blanking-interval-toolkit.html
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Horizontal blanking interval
1 'Horizontal blanking interval' refers to a part of the process of displaying images on a computer monitor or
television display device|screen via raster scanning
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Horizontal blanking interval - HBlank effects
1 The Super Nintendo Entertainment System|Super NES's Mode 7 used the horizontal blanking interval to vary
the scaling and rotation of one background layer on a scanline by
scanline basis to create many different effects
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Local on the 8s - History
1 Weather information is received from the vertical blanking interval of the
TWC video feed and from data transmitted via satellite, which is
then inserted over the TWC feed with local insertion technologies
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ORACLE (teletext) - History
1 Under the original plans for the ITV franchise renewal, they were to have
been scrapped at the end of 1992 and the few Vertical blanking
interval|scan lines they used given to the highest bidder
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CRT TV - Display technology
1 It actually could be slightly higher than that, but the vertical blanking
interval (VBI), allows time for magnetic beam scanning retrace in affordable CRT-equipped television
receivers
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Vertical interval timecode
1 'Vertical Interval Timecode' ('VITC', pronounced vitsee or vits) is a form of SMPTE timecode embedded as a
pair of black-and-white bars in a video signal. These lines are
typically inserted into the vertical blanking interval of the video signal.
There can be more than one VITC pair in a single frame of video: this can be used to encode extra data
that will not fit in a standard timecode frame.
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