HDV
HDV is a format for recording of high-definition video on DV videocassette tape. 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. The format was marketed mainly in the mid and late 2000s. HDV and the HDV logo are trademarks of JVC and Sony.
History
The format was originally developed by JVC and supported by Sony, Canon, and Sharp. The four companies formed the HDV Consortium in September 2003.JVC released its latest HDV camcorder — the GY-HD250 — in 2006. In September 2011 this model was discontinued on the U.S. market. The "B" modification of the older GY-HD200 was released in 2008 and discontinued in November 2009. The latest HDV camcorder made by Canon — the HV40 — was released in 2009, but it traces back to the HV20 developed in 2007, and was phased out of production during 2011, though stocks have lasted through 2012. The latest Sony consumer HDV model is the HDR-HC9, originally released in 2008 and discontinued on the North American market in 2011. 2008 was also the year when Sony presented the latest "advanced amateur" and professional HDV camcorders, namely the HDR-FX1000 and the HVR-Z5.
All the three major manufacturers of HDV equipment — JVC, Canon and Sony — heavily invested in development of MPEG-2 video compression scheme and continued to rely on it in their professional tapeless camcorder lineups: XDCAM HD, XDCAM EX, XDCAM HD422, XF Codec. At the same time Sony, Canon and later JVC joined Panasonic in marketing of AVCHD recording format, which is claimed to deliver visual quality similar to HDV at half the datarate. Consumer high definition camcorders released by these companies since 2009 employ AVCHD format.
In 2010 industry analysts did not expect new HDV products, but believed that manufacturers would continue to support HDV for their existing users, while at the same time transitioning to file-based workflow. When accessed in 2017, the Broadcast & Production Cameras section on Sony's website does not mention HDV technology. The HDV page does not list any equipment or whitepapers.
Video and audio coding
HDV video and audio are encoded in digital form, using lossy inter frame compression. Video is encoded with the H.262/MPEG-2 Part 2 compression scheme, using 8-bit chroma and luma samples with 4:2:0 chroma subsampling. Stereo audio is encoded with the MPEG-1 Layer 2 compression scheme. The compressed audio and video are multiplexed into an MPEG-2 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 video data rate can cause bit rate starvation in scenes that have much 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 384 kbit/s, MPEG-1 Layer 2 audio is regarded as perceptually lossless.
Recording formats
Two major versions of HDV are HDV 720p and HDV 1080i. The former is used by JVC and is informally known as HDV1. The latter is preferred by Sony and Canon and is sometimes referred to as HDV2. The HDV 1080i defines optional progressive recording modes, and in recent publications is sometimes called HDV 1080 or 1080-line HDV as progressive 1080-line recording becomes commonplace.HDV 720p
HDV 720p format allows recording high definition video as well as progressive-scan standard definition video.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 and reality-like frame rates.
HDV-SD is a mode for recording progressive-scan standard definition video. Such a video is sometimes called enhanced definition video, but is considered high definition video in Australia. 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.
JVC was 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".
HDV 1080i
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. 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 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 and records the 2-3 pull-down identification data in the HDV stream, so that compatible NLE software knows when to remove the 2-3 pull-down cadences. Several editing tools, including Sony's own Vegas, are capable of processing 24A video as proper 24 frame/s progressive video.
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. The same or better film look effect can be achieved by converting regular interlaced video into progressive format using computer software.
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. 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.
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.
HDV 1080p
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 the 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 and 29.97 frame/s for 60 Hz markets, and at 25 frame/s 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.
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. Because of row-pair summation, the vertical resolution of progressive video is 10–25% lower than the resolution of interlaced video.
In 2008, Sony released its own models capable of native progressive recording: the HVR-S270, the HVR-Z7 and the HVR-Z5. Sony stressed that the models handle the signal entirely in progressive mode all the way from capture to encoding to recording on tape to output. Sony has designed a Native Progressive Recording logo for the devices that are capable of native progressive recording and playback.
In 2009, Canon released the HV40 HDV camcorder. Its 60 Hz variant, carrying a prominent 24p native progressive mark, became the first consumer HDV model to offer 24-frame/s native progressive recording. Like the aforementioned Sony models, the HV40 uses a true progressive-scan sensor.
Despite differences in branding, native progressive modes offered by Canon and Sony are fully compatible, with both companies adhering to HDV specifications for recording native 1080p video. Other HDV devices capable of reading and recording in native progressive 1080-line format include the Sony HVR-M15AU, HVR-25AU, HVR-M15AE, HVR-25AE and HVR-M35 HDV videocassette recorders, and the 60 Hz Canon HV20/HV30 camcorders when used in tape recorder mode.