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HDV is a format for recording of high-definition video on DV cassette tape.[1] The format was originally developed by JVC and supported by Sony, Canon and Sharp.[2] The four companies formed the HDV consortium in September 2003. Conceived as an affordable high definition format for digital camcorders, HDV quickly caught on with many amateur and professional videographers due to its low cost, portability, and image quality acceptable for many professional productions. HDV and HDV logo are trademarks of JVC and Sony.HDV video and audio are encoded in digital form, using lossy compression. Video is encoded with the MPEG-2 codec, using 8-bit chroma and luma samples with 4:2:0 chroma subsampling. Stereo audio is encoded with the MPEG-1 Layer 2 codec. The compressed audio and video are multiplexed into a MPEG transport stream, which is typically recorded onto magnetic tape, but can also be stored in a computer file. The data rate for both the audio and video is constant and is roughly the same as DV data rate. The relatively low data rate can cause bit rate starvation in scenes that have lots of fine detail, rapid movement or other complex activity like flashing lights, and may result in visible artifacts, such as blockiness and blurring. In contrast to the video, HDV audio bitrate is relatively generous. At the coded bitrate of 384kbit/s, MPEG-1 Layer 2 audio is regarded as perceptually lossless. HDV 720p HDV 720p format allows recording high definition video (HDV-HD) as well as progressive-scan standard definition video (HDV-SD).[7] HDV-HD closely matches broadcast 720p progressive scan video standard in terms of scanning type, frame size, aspect ratio and data rate. Earlier HDV 720p camcorders could shoot only at 24, 25 and 30 frames per second. Later models offer both film-like (24p, 25p, 30p) and reality-like (50p, 60p) frame rates. HDV-SD is a mode for recording progressive-scan standard definition video. Such a video is sometimes called enhanced definition video (EDTV), but is considered high definition video in Australia.[8] Depending on region, HDV-SD video is recorded either as 576p50 or as 480p60. Like DVCPRO Progressive, HDV-SD was meant as an intermediate format during the transition time from standard definition to high definition video. Later models of HDV 720p camcorders do not record in this mode. Presently, JVC is the only manufacturer of HDV 720p camcorders. JVC was the first to release an HDV camcorder, the handheld GR-HD1. Later JVC shifted its HDV development to shoulder-mounted cameras. A common misconception is that JVC developed a proprietary extension to HDV called ProHD, featuring film-like 24-frame/s progressive recording mode and LPCM audio, for professional use. JVC has clarified that ProHD is not a video recording format, but "an approach for delivering affordable HD products" and a common name for "bandwidth efficient professional HD models".Sony adapted HDV, originally conceived as progressive-scan format by JVC, to interlaced video. Interlaced video has been a useful compromise for decades due to its ability to display motion smoothly while reducing recording and transmission bandwidth. Interlaced video is still being used in acquisition and broadcast, but interlaced display devices are being phased out. Modern flat-panel television sets that utilize plasma and LCD technology are inherently progressive. All modern computer monitors use progressive scanning as well. Before interlaced video is displayed on a progressive-scan device it must be converted to progressive using the process known as deinterlacing. Progressive-scan television sets employ built-in deinterlacing circuits to cope with interlaced broadcast signal, but computer video players rarely have this capability. As such, interlaced video may exhibit ghosting or combing artifacts when watched on a computer. Some HDV 1080i camcorders are capable of recording progressive video within an interlaced stream, provided that the frame rate does not exceed half of the field rate. The first HDV 1080i camcorder to implement such Progressive Scanning was the Sony HVR-V1.[9] To preserve compatibility with interlaced equipment the HVR-V1 records and outputs video in interlaced form. 25-frame/s and 30-frame/s progressive video is recorded on tape using progressive segmented frame (PsF) technique, while 24-frame/s recording employs 2-3 pulldown. The camcorder offers two variations of 24-frame/s recording: "24" and "24A". In "24" mode the camera ensures that there are no cadence breaks for a whole tape, this mode works better for watching video directly from the camera and for adding "film look" to interlaced video. In the "24A" mode the camera starts every clip on an A frame with timecode set to an even second margin.[10][11] Several editing tools, including Sony's own Vegas, are capable of processing 24A video as proper 24 frame/s progressive video.[12] Prior to the HVR-V1, Sony was offering Cineframe, essentially an interlaced-to-progressive converter, to simulate film-like motion. The conversion process involved blending and discarding fields, so vertical resolution of the resulting video suffered. Motion, produced in the 24-frame/s variant of Cineframe was too uneven for professional use.[13] The same or better film look effect can be achieved by converting regular interlaced video into progressive format using computer software.[14] In 2007 Canon commoditized progressive scanning, releasing the HV20 camcorder. The version for 50 Hz market featured PF25 mode with PsF-like recording, while the version for 60 Hz market had PF24 mode, which utilized 2-3 pulldown scheme. Progressive scan video recorded with the HV20 does not include flags necessary for performing automated film-mode deinterlacing, which is why most editing tools treat such video as interlaced.[15] The HV30, released in 2008, implemented additional PsF-like PF30 mode for 60 Hz markets. Output is performed via component, HDMI and FireWire in interlaced form.[16] Progressive scan video must be properly deinterlaced to achieve full vertical resolution and to avoid interlace artifacts. 25P and 30P video must be deinterlaced with "weave" or "no deinterlacing" algorithm, which means joining two fields of each frame together into one progressive frame. This operation can be done in most editing tools simply by changing project properties from interlaced to progressive. 24P video must go through film-mode deinterlacing also known as inverse telecine, which throws out judder frames and restores original 24-frame/s progressive video. Many editing tools cannot perform film-mode deinterlacing, requiring usage of a separate converter. [edit] HDV 1080p Native Progressive Recording logo (Sony) Native Progressive logo (Canon) The original 1080-line HDV specification defined interlaced recording only, which is suitable for television broadcast. As users have become increasingly interested in digital cinematography and in web videos, progressive recording became a necessity. In response to this need, capability for native progressive recording has been added to the 1080i HDV specification. Progressive recording modes are optional for 1080i HDV devices, which means that not every HDV 1080i camcorder or deck is capable of recording or playing back native progressive video. Because HDV 1080i specification now includes both interlaced and progressive recording modes, in recent publications it is often called HDV 1080 or 1080-line HDV, but the official name still bears the "i" suffix. HDV camcorders capable of native 1080-line progressive video record it at rates of 23.98 frame/s (commonly referred to as "24p") and 29.97 frame/s ("30p") for 60 Hz markets, and at 25 frame/s ("25p") for 50 Hz markets. Video is output as true progressive video via an i.LINK/Firewire port. Output through other ports is performed in interlaced mode to preserve compatibility with existing interlaced equipment.[17][18] The first 1080-line HDV camcorder to offer recording in native progressive format was the Canon XL H1, introduced in 2006. It was followed by the XH-G1 and XH-A1. When shooting in progressive mode, also known as Frame mode, these camcorders generate progressive video from interlaced CCD sensors.[19] Because of row-pair summation,[20] vertical resolution of progressive video is 10%-25% lower than resolution of interlaced video.[21][22] In 2008 Sony released its own models capable of native progressive recording: the HVR-S270, the HVR-Z7 and the HVR-Z5. Sony claims superiority over Canon models by saying that native progressive recording has been called 24F/25F/30F in some camcorders, which actually use interlaced CCD imagers.[5] Sony stresses that its own models process the signal entirely in progressive mode all the way from capture to encoding to recording to output.[23] In 2009 Canon released the HV40. Its 60 Hz variant became the first consumer HDV camcorder to feature 24-frame/s native progressive recording. Like the aforementioned Sony models, the HV40 uses true progressive-scan sensor.[24] Until release of the HV40, which bears 24p native progressive mark, Canon had no special logo to identify cameras that could record in progressive mode. Sony designed Native Progressive Recording logo for the devices that are capable of native progressive recording and playback. Despite differences in branding, native progressive modes offered by Canon and Sony are fully compatible, because both companies follow HDV specifications for recording native 1080p video.[25][26][27][28][29] Other HDV devices capable of reading and recording in native progressive 1080-line format include the Sony HVR-M15AU, HVR-25AU,[30] HVR-M15AE, HVR-25AE[31] and HVR-M35 HDV videocassette recorders, and the Canon HV20/HV30 camcorders when used in tape recorder mode. [edit] Compatibility Generally, HDV devices are capable of playing and recording in DV format, though this is not required by HDV specification. Many HDV devices manufactured by Sony are capable of playing and recording in DVCAM format. 1080-line devices generally are not compatible with 720-line devices, though some standalone tape decks accept both HDV flavors. Devices that can play and record native 1080p video can play and record native 1080i video, however the opposite is not always the case. HDV , or CGA installed in the same machine. At the beginning of the 1980s, this was typically used to display Lotus 1-2-3 spreadsheets in high-resolution text on a MDA display and associated graphics on a low-resolution CGA display simultaneously. Many programmers also used such a setup with the monochrome card displaying debugging information while a program ran in graphics mode on the other card. Several debuggers, like Borland's Turbo Debugger, D86 (by Alan J. Cox) and Microsoft's CodeView could work in a dual monitor setup. Either Turbo Debugger or CodeView could be used to debug Windows. There were also DOS device drivers such as ox.sys, which implemented a serial interface simulation on the MDA display and, for example, allowed the user to receive crash messages from debugging versions of Windows without using an actual serial terminal. It is also possible to use the "MODE MONO" command at the DOS prompt to redirect the output to the monochrome display. When a Monochrome Display Adapter was not present it was possible to use the 0xB000 – 0xB7FF address space as additional memory for other programs (for example by adding the line "DEVICE=EMM386.EXE I=B000-B7FF" into config.sys, this memory would be made available to programs that can be "loaded high" – loaded into high memory.)The VGA color system is backwards compatible with the EGA and CGA adapters, and adds another level of configuration on top of that. CGA was able to display up to 16 colors, and EGA extended this by allowing each of the 16 colors to be chosen from a 64-color palette (these 64 colors are made up of two bits each for red, green and blue: two bits × three channels = six bits = 64 different values). VGA further extends this scheme by increasing the EGA palette from 64 entries to 256 entries. Two more blocks of 64 colors with progressively darker shades were added, along with 8 "blank" entries that were set to black.[12][dubious – discuss] In addition to the extended palette, each of the 256 entries could be assigned an arbitrary color value through the VGA DAC. The EGA BIOS only allowed 2 bits per channel to represent each entry, while VGA allowed 6 bits to represent the intensity of each of the three primaries (red, blue and green). This provided a total of 64 different intensity levels for red, green and blue, resulting in 262,144 possible colors, any 256 of which could be assigned to the palette (and in turn out of those 256, any 16 of them could be displayed in CGA video modes). This method allowed new VGA colors to be used in EGA and CGA graphics modes, providing one remembered how the different palette systems are laid together. To set the text color to very dark red in text mode, for instance, it will need to be set to one of the CGA colors (for example, the default color, #7: light grey.) This color then maps to one in the EGA palette—in the case of CGA color 7, it maps to EGA palette entry 42. The VGA DAC must then be configured to change color 42 to dark red, and then immediately anything displayed on the screen in light-grey (CGA color 7) will become dark red. This feature was often used in 256-color VGA DOS games when they first loaded, by smoothly fading out the text screen to black. (The game Descent, from 1995, is an example.) While CGA and EGA-compatible modes only allowed 16 colors to be displayed at any one time, other VGA modes, such as the widely used mode 13h, allowed all 256 palette entries to be displayed on the screen at the same time, and so in these modes any 256 colors could be shown out of the 262,144 colors available.