HDV
From Wikipedia, the free encyclopedia
HDV is a format for recording and playback of high-definition video on a DV cassette tape.[1] The format was developed by JVC and Sony and initially supported by Canon and Sharp. The four companies formed the HDV consortium in September 2003. Initially conceived as a consumer-oriented format, HDV quickly caught on with many professional users due to its low cost, portability and image quality acceptable for many professional productions.
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.[2] The HDV 1080i defines optional progressive recording modes, and in recent publications is often called HDV 1080 or 1080-line HDV as progressive 1080-line recording becomes commonplace.[3][4]
Most HDV camcorders use "small" MiniDV/DVC cassettes. Some shoulder-mount camcorders are also capable of recording onto "large" DV/DVCAM cassettes. The recording time is the same as DV Standard Play. Unlike DV, HDV does not offer Long Play speed.
HDV is backwards compatible with DV, meaning that HDV equipment can play and record DV content. On the other hand, DV devices cannot play nor record in HDV format.
HDV and HDV logo are trademarks of Sony and JVC.[5]
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[edit] HDV 720p
HDV 720p closely matches broadcast 720p video standard in terms of scanning type, frame rate, frame size, aspect ratio and data rate. 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 separate format, but "an approach for delivering affordable HD products" and a common name for "bandwidth efficient professional HD models". JVC has stressed out that 24-frame/s progressive recording and LPCM recording/playback have always been part of the HDV format specification.[6]
[edit] HDV 1080i
HDV 1080i is an interlaced video standard. 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. Interlaced video must be converted to progressive before it is displayed on a progressive-scan device. The process of converting interlaced video into progressive is known as deinterlacing. Progressive-scan television sets employ built-in deinterlacing circuits to cope with interlaced broadcast signal, but computers rarely have this capability. As such, native interlaced video must be deinterlaced if it is intended for viewing 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.[7] 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", the latter is also known as "24pSCNA". When switched to "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"/"24pSCNA" mode the camera starts every clip on an A frame with timecode set to an even second margin.[8][9]
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. Because the camera was still shooting in interlaced mode, slower frame rate did not improve light sensitivity. In addition, motion, produced in the 24-frame/s variant of Cineframe was too uneven for professional use.[10] The same or better film look effect could be achieved by converting regular interlaced video into progressive format using computer software.[11]
In 2007 Canon commoditized progressive scanning, releasing the HV20 camcorder. The version for 50Hz market featured PF25 mode with PsF-like recording, while the version for 60Hz market had PF24 mode, which utilized 2-3 pulldown scheme. 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.[12]
To achieve full vertical resolution without introducing interlace artifacts the progressive scan video must be properly deinterlaced. 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. 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.
[edit] HDV 1080p
There is no separate standard for HDV 1080p recording. Instead, the HDV 1080i specification defines optional progressive recording modes, which are getting popular as the users become more interested in shooting digital movies and creating content for the Web. All HDV camcorders that can record in 1080p format can also record native 1080i video.
HDV camcorders, capable of 1080-line progressive video, record it at rates of 24 frame/s (actually 23.98 frame/s) and 30 frame/s (actually 29.97 frame/s) for 60 Hz markets, and at 25 frame/s rate 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.[13][14]
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 the XH-G1 and XH-A1. When shooting in progressive mode, also known as Frame mode, the camcorders generate progressive video from interlaced CCD sensors.[15] Vertical resolution of the resulting video is about 25% lower than theoretically possible because of row-pair summation, but is still higher than the resolution of a single field.[16] Video shot in Frame Mode is recorded to tape according to HDV native 1080p specifications.
In 2008 Sony released the HVR-S270, HVR-Z7 and HVR-Z5 models, capable of recording of progressive video. Unlike Canon camcorders that use interlaced sensors, the Sony camcorders use progressive sensors, which is emphasized by the name that Sony gave to this mode: Native Progressive Recording. Sony claims superiority over Canon models by saying that Native Progressive Recording has been called 24F/25F/30F in some camcorders, while actually using interlace CCD imagers.[3]
In January 2009 Canon announced the HV40 as a replacement for the HV30 consumer camcorder. Aside of minor cosmetic changes, the 60 Hz model sports 24- frame/s native progressive recording and uses the same progressive-scan CMOS sensor as the models it replaces.[17]
Sony designed a "Progressive" logo for the camcorders that are capable of native progressive recording. Canon has no special logo to identify cameras that can record in frame modes. Despite of the differences in branding, 24F/25F/30F modes offered by Canon and Native Progressive Recording offered by Sony are compatible.
Aside of aforementioned camcorders, other products that are capable of reading and recording in native progressive format are the Sony HVR-M15AU, HVR25AU,[18] HVR-M15AE, HVR25AE[19] and HVR-M35 HDV videocassette recorders, and the Canon HV20/HV30 camcorders when used in tape recorder mode.
[edit] Compatibility between brands
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 able of playing and recording DVCAM tapes. 1080-line devices generally are not compatible with 720-line devices, though some standalone tape decks accept both HDV formats. Devices that can play and record native 1080p video can play and record native 1080i video, the opposite is not always the case.
[edit] HDV compression
HDV is based on MPEG-2 video, which compresses data both within each frame (intraframe/spatial compression) and between frames (interframe/temporal compression). This is the same type of compression used for DVD video and many network TV broadcasts, and allows HDV to achieve high spatial resolution at low data rates compared to other HD recording formats. HDV 1080i uses a recording data rate of 25 Mbit/s (3.125 MB/s) while HDV 720p records at 19.7 Mbit/s (2.46 MB/s). In either case the data rate is constant because the recording media — tape — is transported with constant speed.
Using MPEG-2 video enables HDV to achieve a higher compression ratio than recording formats without interframe compression, but constant data rate limits the video quality in scenes with lots of detail, rapid movement or other complex activity like flashing lights. Such scenes may exhibit visible artifacts such as blockiness or blurring, depending on the amount of movement and on the algorithm employed in the encoder. On contrary, when using a tapeless recording standard such as XDCAM or AVCHD it is possible to increase or decrease the data rate depending on complexity of a scene, thereby preserving quality of a busy scene while saving recording space on a low-detail scene.
Interframe compression also means that a recording dropout in HDV can affect several frames of video rather than just one, since the compression introduces dependency between frames. Hence it is best to use high-quality tapes for HDV recording such as "master quality" Mini-DV or specially formulated HDV tapes, and limit the re-use of tapes. Some users have gotten good results with HDV using generic Mini-DV tapes, but this is not generally recommended.
For audio, HDV uses MPEG-1 Layer 2 compression to reduce the audio bitrate to 384 kbit/s, compared to 1536 kbit/s for DV video and 1411 kbit/s for audio CDs. This makes HDV audio less desirable for situations where sound quality is critical, but MPEG-1 audio at 384 kbit/s is considered 'perceptually lossless.' For general video recording with an on-camera microphone, HDV audio is not a significant limiting factor.
It is important to view HDV's compression limitations in the proper context. Other HD codecs using lower compression ratios need more bandwidth and storage capacity for a given amount of video, requiring significantly more complex and expensive recording solutions. For example, the Panasonic DVCPRO P2 cameras use memory cards which can cost over $50 per minute of recording capacity, compared to a few dollars per hour for Mini-DV tapes. This cost differential has helped make HDV a popular HD recording format for consumers, independent videographers and low-budget TV programs. Another cost-efficient HD recording option became available in October 2008 with a release of the Panasonic HMC150 camera, which records onto readily available SDHC memory cards using the AVCHD encoding.
[edit] Use of HDV in broadcast television
HDV is accepted with varying restrictions for broadcast TV use. It has been used for shows like "Deadliest Catch" and "Mythbusters", and was used in the TV series "JAG" for scenes where larger HD cameras would have been impractical. The BBC currently considers HDV a "non-broadcast domestic HD format," but accepts HDV footage for up to 25% of HD programming content with advance approval.[20]
The preferred delivery formats for Discovery HD Theater are HD-D5 and HDCAM. HDV source content is accepted if it is limited to 15% of a whole program and is shot with a 1080-line camera. Producers wishing to use HDV are required to submit an approved postproduction path outlining their handling of the footage in the editing process.[4] However, the main Discovery Channel's HD simulcast has fewer or no guidelines and accepts a mix of XDCAM HD, HDV and AVCHD for the length of a program.
[edit] Editing HDV
HDV footage can be effectively edited by most modern non-linear editors on fast personal computers. Performance may be reduced compared to other video formats due to both the high resolution and interframe compression, both of which require computers to work harder when calculating editing effects. Performance can be improved by converting HDV to alternative "intermediate" codecs prior to editing, including Cineform Aspect HD, Edius HQ and Apple ProRes 422. There are many advantages to editing HDV using an intermediate codec rather than the native MPEG2 file, however the trade-off is that the file size is substantially increased.
[edit] Products
[edit] JVC
JVC was the first to release an HDV camcorder, the GR-HD1. The GR-HD1 allowed to choose from a selection of resolutions: standard DV (480i), HDV 720p30, or HDV 480p60. Curiously, the HDV modes used the old 601 color space standard, rather than the newer 709 standard intended for high-definition video. The GR-HD1's imager used a single 1/3" CCD sensor instead of a 3CCD setup, another unusual choice discouraging professional use. Due to this, along with other limitations, the GR-HD1 was not popular in either the consumer or semi-professional market. JVC later shifted their HDV development to shoulder-mounted cameras.
[edit] Sony
Sony specializes in 1080i HDV equipment and makes products for both 60 Hz and 50 Hz markets. Traditionally, Sony uses suffix "E" to identify 50 Hz models, and suffix "U" or no suffix at all to identify 60 Hz models. Models listed below are specified without suffixes.
In September 2004 Sony released the first HDV 1080i camcorder, the HDR-FX1. Its professional version, the HVR-Z1, came with XLR audio inputs and 44 additional features. Most notably, the HVR-Z1 was switchable between 50 Hz and 60 Hz scanning to cater for the different scanning rates used in different markets.
In the middle of 2005 Sony released its first consumer HDV model, the HDR-HC1, which had a single CMOS sensor, electronic stabilization system and was capable of recording in DV and HDV 1080i modes. Its professional version, the HVR-A1, added a second accessory shoe in place of the flash, XLR audio inputs, additional recording options, larger eyecup and larger lens hood.
In 2006 Sony replaced the HDR-HC1 with the smaller and cheaper HDR-HC3, which featured an incrementally improved CMOS chip, but omitted some features of its predecessor. The HDR-HC3 was replaced by the HDR-HC5 which used the same CMOS chip as the HDR-HC3, and added an option of recording in xvYCC color space. The replacement model, the HDR-HC7 came with a higher pixel count CMOS sensor and with a microphone input. Like the HDR-HC5, the HDR-HC7 could also record xvYCC. In 2008 the HDR-HC7 was replaced with the HDR-HC9.
In 2006, Sony added two new models to its upscale HDV lineup: the consumer HDR-FX7 and its professional cousin, the HVR-V1. The progressive-scan CMOS sensors of these models resolved full 1920x1080 resolution. 1080p capability of the HVR-V1 allowed the operator the choice of shooting interlaced or progressive video, which was converted to interlaced for recording on tape.
In August 2007, Sony introduced the shoulder-mounted version of the HDR-HC9, the HVR-HD1000. It has a lens similar in size to that of the HVR-Z1 or HVR-V1.[21]
In November 2007, Sony announced the HVR-Z7 handheld camcorder and the HVR-S270 shoulder-mounted camera. Both use the same three 1/3" ClearVid CMOS sensors and attain light sensitivity similar to that of the SD DSR-PD170 while offering HDV recording in native interlaced, progressive scan and native progressive modes. The Z7 has 2 XLR audio inputs and HDMI output while the S270 has 4 XLR inputs and features HD-SDI output.[22]
In 2008 the HVR-FX1 was replaced with the HVR-FX1000, and the HVR-Z1 was replaced with the HVR-Z5. Aside of multitude of improvements, the FX1000 can record progressive scan video like the HVR-V1, while the HVR-Z5 offers native progressive recording mode.[23]
In November 2008 Sony restarted production of the HDR-FX7 camcorder, which had been discontinued a year earlier. Offered for almost half the original price, the HDR-FX7 bridges the gap between the HDR-HC9 and the FX1000.
[edit] Canon
Canon entered the HDV market in September 2005, with the Canon XL H1, a professional-oriented modular camera system with interchangeable lenses, HD-SDI output, and three 1440x1080 1/3" CCDs. In July 2006, Canon announced their XH A1 and XH G1 models, which use the same sensor as the XL-H1 but in a smaller form factor with a (non-changeable) fixed lens. Canon then introduced the consumer oriented Canon HV10, a compact unit with a single 2.76 Megapixel CMOS sensor. In April 2007 Canon released the updated Canon HV20 which adds a 24p Progressive + film mode where the imager captures 24 progressive frames per second, but records to 1080/60i HDV using a built-in 3:2 pulldown (telecine) process, to remain compatible with consumer level editing suites. The current consumer model (HV30), has a black body instead of the HV20's grey one, and added a 30P mode to simplify video-uploads to online sites (such as YouTube and Vimeo.)
[edit] Sharp
Sharp is the only member of the HDV Consortium that has not produced an HDV camcorder or a videocassette recorder. The closest Sharp has ever got in supporting HDV standard is the AQUOS DV-ACV52 digital video player. The player supports HDV video, though it does not have a tape transport. Instead, it allows playback and dubbing of DV/HDV video from a camcorder connected to the player via a FireWire connector.
[edit] Alternatives
Some alternatives to HDV for moderately-priced HD recording include the following:
- The AVCHD format uses the H.264 codec based on MPEG4 compression, with recording on solid-state flash memory, hard drives and 8cm DVDs. Panasonic has a variation of AVCHD called AVCCAM with a bit rate up to 24 Mbit/s.
- The Sony 'XDCAM EX' format uses MPEG2 compression at a data rate up to 35 Mbit/s, recording on "SxS" memory cards developed by Sony and Sandisk.
- The DVCPRO HD format from Panasonic uses a data rate up to 100 Mbit/s, recording on solid state DVCPRO P2 cards.
- Some digital photography cameras (e.g. Canon 5D Mark II) now offer HD video recording modes.
[edit] Specifications
The table below lists three HDV formats: HDV 720p, HDV 1080i and HDV 1080p, this is done for convenience only. HDV 1080p is not officially defined as a separate standard, but is included instead into HDV 1080i specification as optional format. All HDV camcorders that are capable of 1080p recording can also record native 1080i video.
| Format | HDV 720p | HDV 1080i | HDV 1080p |
|---|---|---|---|
| Media | Full-size DV or compact DVC cassette | ||
| Video | |||
| Scanning type | progressive | interlaced | progressive |
| Frame aspect ratio | 16x9 | ||
| Frame size in pixels | 1280 x 720 | 1440 x 1080 | |
| Pixel aspect ratio | 1.0 | 1.33 | |
| Video signal | 720/60p, 720/30p, 720/50p, 720/25p, 720/24p | 1080/60i, 1080/50i | 1080/30p, 1080/25p, 1080/24p |
| Video Compression | MPEG2 Video (profile & level: MP@HL) | MPEG2 Video (profile & level: MP@H-14) | |
| Sampling frequency for luminance | 74.25 MHz | 55.6875 MHz | |
| Chroma sampling format | 4:2:0 | ||
| Quantization | 8 bits (both luminance and chrominance) | ||
| Compressed video bitstream rate | ~19.7 Mbit/s | ~25 Mbit/s | |
| Audio | |||
| Compression | MPEG-1 Audio Layer II, PCM | MPEG-1 Audio Layer II | |
| Sampling frequency | 48 kHz | ||
| Quantization | 16 bits | ||
| Audio modes and data rate | Stereo (2-channel) at 384 kbit/s (192 kbit/s per channel); optional 4-channel at 96 kbit/s per channel. |
||
| System | |||
| Stream type | MPEG-2 transport stream (MPEG-2 TS) | ||
| Stream interface | IEEE 1394 in alpha mode (also known as FireWire 400 or i.LINK) | ||
| File extension | .m2t (generally) | ||
[edit] See also
[edit] References
- ^ "HDV Press Release". http://www.hdv-info.org/page2.htm.
- ^ "Editing HDV". http://www.eventdv.net/Articles/ReadArticle.aspx?ArticleID=37958.
- ^ a b "HDV progressive primer". http://www.sony.ca/hdv/files/white/HDV_Progressive_Primer.pdf.
- ^ a b "Discovery HD Theater production requirements". http://dhd.discovery.com/guidelines/gallery/guidelines.pdf.
- ^ "HDV Trademarks". http://www.hdv-info.org/trademk.htm.
- ^ "JVC clarifies ProHD announcement". http://jvc.broadcastnewsroom.com/articles/viewarticle.jsp?id=32220.
- ^ [http://www.camcorderinfo.com/content/Sony-Introduces-HVR-V1U-and-HDD-Unit-in-US.htm "Camcorderinfo.com: Sony Introduces HVR-V1U and HDD Unit in the U.S."]. http://www.camcorderinfo.com/content/Sony-Introduces-HVR-V1U-and-HDD-Unit-in-US.htm.
- ^ "dv.com: Sony HVR-V1 review". http://www.dv.com/reviews/reviews_item.php?articleId=196602843.
- ^ "DVInfo: EXPLAINED: "24" versus "24A"". http://www.dvinfo.net/conf/sony-hvr-v1-hdr-fx7/82350-explained-24-verses-24a.html.
- ^ [http://www.adamwilt.com/HDV/cineframe.html "Adam Wilt, How the Sony HDV cameras fake 24, 25, and 30 frame/s"]. http://www.adamwilt.com/HDV/cineframe.html.
- ^ [http://www.hdtvexpert.com/pages_b/hdrfx1.html "Steve Mullen, Sony's HDR-FX1 1080i HDV Camcorder: using CineFrame 24 mode"]. http://www.hdtvexpert.com/pages_b/hdrfx1.html.
- ^ "Canon 24P, 25F, 25P, 30F, 30P modes explained". http://www.avchduser.com/articles/canon_progressive_modes.jsp.
- ^ "Sony HVR-Z5U Digital HD Video Camera Recorder". http://www.papahui.com/download.pdf.
- ^ "Sony HVR-Z5E preliminary datasheet". http://www.sony.co.uk/res/attachment/file/97/1219910881397.pdf.
- ^ "Canon XL H1: frame rates & formats". http://www.usa.canon.com/app/html/XLH1/frame_rates_formats.shtml.
- ^ Progressive: what you need to know
- ^ "Canon U.S.A. packs a punch with a powerful new camcorder line-up for 2009". http://www.usa.canon.com/templatedata/pressrelease/20090105_camcorders.html.
- ^ "Sony adds new features to HDV videotape recorders (America". http://news.sel.sony.com/en/press_room/b2b/broadcast_production/pro_audio_video/release/34858.html.
- ^ "Sony adds new features to HDV videotape recorders (Europe)". http://www.sony.co.uk/biz/view/ShowPressRelease.action?section=SB+SS+ALL+Press+Center&pressrelease=1207064692287&site=biz_en_GB.
- ^ "TV Delivery for BBC Worldwide". BBC Worldwide. http://www.bbc.co.uk/guidelines/dq/pdf/tv/tv_standards_worldwide.pdf. section 1.5.2
- ^ "HVR-HD1000U Press Release (Sony)". http://news.sel.sony.com/en/press_room/b2b/broadcast_production/release/31159.html.
- ^ "EventDV article on Sony HVR-Z7U". http://www.eventdv.net/Articles/ReadArticle.aspx?ArticleID=41396.
- ^ "Sony's HDR-FX1000 breaks the mold". http://www.bhphotovideo.com/find/newsLetter/HDR-FX1000.jsp.
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