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Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Ghost-canceling reference (GCR) is a special sub-signal on a television channel that receivers can use to compensate for the ghosting effect of a television signal distorted by multipath propagation between transmitter and receiver.
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 (line 19 in the U.S.), 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 an adaptive equalizer that removes ghost images on the screen.
GCR was introduced after its recommendation in 1993 by the Advanced Television Systems Committee.[1]
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Ghost-canceling reference (GCR) is a special sub-signal on a television channel that receivers can use to compensate for the ghosting effect of a television signal distorted by multipath propagation between transmitter and receiver. 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 (line 19 in the U.S.), 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 an adaptive equalizer that removes ghost images on the screen. GCR was introduced after its recommendation in 1993 by the Advanced Television Systems Committee.
In a raster scan display, the vertical blanking interval (VBI), also known as the vertical interval or VBLANK, is the time between the end of the final visible line of a frame or field and the beginning of the first visible line of the next frame or field. It is present in analog television, VGA, DVI and other signals. Here the term field is used in interlaced video, and the term frame is used in progressive video and there can be a VBI after each frame or field. In interlaced video a frame is made up of 2 fields. Sometimes in interlaced video a field is called a frame which can lead to confusion. In raster cathode-ray tube (CRT) displays, the blank level is usually supplied during this period to avoid painting the retrace line—see raster scan for details; signal sources such as television broadcasts do not supply image information during the blanking period. Digital displays usually will not display incoming data stream during the blanking interval even if present. The VBI was originally needed because of the inductive inertia of the magnetic coils which deflect the electron beam vertically in a CRT; the magnetic field, and hence the position being drawn, cannot change instantly. Additionally, the speed of older circuits was lower than today’s. For horizontal deflection, there is also a pause between successive lines, to allow the beam to return from right to left, called the horizontal blanking interval. 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). Blanking of a CRT may not be perfect due to equipment faults or brightness set very high; in this case a white retrace line shows on the screen, often alternating between fairly steep diagonals from right to left and less-steep diagonals back from left to right, starting in the lower right of the display. 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, VITC timecode, closed captioning, teletext, CGMS-A copy-protection indicators, and various data encoded by the XDS protocol (e.g., the content ratings for V-chip use) and other digital data can be sent during this time period. In U.S. analog broadcast television, line 19 was reserved for a Ghost-canceling reference and line 21 was reserved for NABTS captioning data. Teletext contemplated the use of line 22 for data transmission. The pause between sending video data is sometimes used in real time computer graphics to modify the frame buffer, or to provide a time reference for when switching the source buffer for video output can happen without causing a visible tear. This is especially true in video game systems, where the fixed frequency of the blanking period might also be used to derive in-game timing. On many consoles there is an extended blanking period, as the console opts to paint graphics on fewer lines than the television would natively allow, permitting its output to be surrounded by a border. On some very early machines such as the Atari 2600, the programmer is in full control of video output and therefore may select their own blanking period, allowing arbitrarily few painted lines. On others such as the Nintendo Entertainment System, a predefined blanking period could be extended. Most consumer VCRs use the known black level of the vertical blanking pulse to set their recording levels. The Macrovision copy protection scheme inserts pulses in the VBI, where the recorder expects a constant level, to disrupt recording to videotapes.
Below are the published ATSC standards for ATSC digital television service, issued by the Advanced Television Systems Committee. A/49: Ghost Canceling Reference Signal for NTSC (for adjacent-channel interference or co-channel interference with analog NTSC stations nearby) A/52B: audio data compression (Dolby AC-3 and E-AC-3) A/53E: "ATSC Digital Television Standard" (the primary document governing the standard) A/55: "Program Guide for Digital Television" (now deprecated in favor of A/65 PSIP) A/56: "System Information for Digital Television" (now deprecated in favor of A/65 PSIP) A/57A: "Content Identification and Labeling for ATSC Transport" (for assigning a unique digital number to each episode of each TV show, to assist DVRs) A/63: "Standard for Coding 25/50 Hz Video" (for use with PAL and SECAM-originated programming) A/64A "Transmission Measurement and Compliance for Digital Television" A/65C: "Program and System Information Protocol for Terrestrial Broadcast and Cable" (PSIP includes virtual channels, electronic program guides, and content ratings) A/68: "PSIP Standard for Taiwan" (defines use of Chinese characters via Unicode 3.0) A/69: recommended practices for implementing PSIP at a TV station A/70A: "Conditional Access System for Terrestrial Broadcast" A/71: "ATSC Parameterized Services Standard" A/72: "Video System Characteristics of AVC in the ATSC Digital Television System" (implementing H.264/MPEG-4 as well as MVC for 3D television) A/76: "Programming Metadata Communication Protocol" (XML-based PMCP maintains PSIP metadata though a TV station's airchain) A/79: "Conversion of ATSC Signals for Distribution to NTSC Viewers" (recommended practice, issued February 2009) A/80: "Modulation and Coding Requirements for Digital TV (DTV) Applications Over Satellite" (ATSC-S) A/81: "Direct-to-Home Satellite Broadcast Standard" (not yet implemented by any services) A/82: "Automatic Transmitter Power Control (ATPC) Data Return Link (DRL) Standard" A/85: "Techniques for Establishing and Maintaining Audio Loudness for Digital Television" A/90: "Data Broadcast Standard" (for datacasting) A/92: "Delivery of IP Multicast Sessions over Data Broadcast Standard" (for IP multicasting) A/93: "Synchronized/Asynchronous Trigger Standard" A/94: "ATSC Data Application Reference Model" A/95: "Transport Stream File System Standard" (TSFS is a special file system for downloading computer files) A/96: "ATSC Interaction Channel Protocols" (interactive TV) A/97: "Software Data Download Service" (used by UpdateTV for upgrades and software patches in ATSC tuners) A/98: "System Renewability Message Transport" A/99: "Carriage Of Legacy TV Data Services" (for former analog supplemental services that used the vertical blanking interval lines, such as closed captioning and teletext) A/100: "DTV Application Software Environment - Level 1" (DASE-1) A/101: "Advanced Common Application Platform" (ACAP) A/103:2014: "Non-Real-Time Delivery" A/104: "ATSC 3D-TV Terrestrial Broadcasting" A/105:2015: "Interactive Services Standard" A/106:2015: "ATSC Security and Service Protection Standard" A/107:2015: "ATSC 2.0 Standard" A/110A: "Synchronization Standard for Distributed Transmission" (single-frequency networks) A/112: E-VSB (Enhanced Vestigal Sideband) A/153: ATSC-M/H In 2004, the main ATSC standard was amended to support Enhanced ATSC (A/112); this transmission mode is backwardly compatible with the original 8-Bit Vestigal Sideband modulation scheme, but provides much better error correction. ATSC-M/H for mobile TV has been approved and added to some stations, though it is known that it uses MPEG-4 instead of MPEG-2 for encoding, and behaves as an MPEG-4-encoded subchannel, inheriting 8VSB from the remainder of the channel.
The Ghost Busters is a live-action children's sitcom that ran on CBS in 1975, about a team of bumbling detectives who investigate ghostly occurrences. The show reunited Forrest Tucker and Larry Storch in slapstick roles similar to their characters in F Troop, and featured a third actor, Bob Burns, in a gorilla suit as their partner. The series of fifteen episodes centered on the perpetual bumbling of the characters, good and evil alike. Character names referenced classic cinema, with both "Spencer" and "Tracy" alluding to actor Spencer Tracy, while "Kong" – not given to the gorilla – was a homage to King Kong. After Columbia Pictures paid to license the Filmation series name for their (unrelated) 1984 film Ghostbusters, Filmation revived its series with an animated sequel in 1986.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.