HDV

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HDV is an inexpensive high-definition video recording format which uses MPEG2 compression to fit HD content onto the same DV or MiniDV tapes originally developed for standard definition recording. The compression used results in some quality compromises compared to higher bandwidth HD recording formats, but has still proved useful for many purposes including several popular TV shows. (However, most TV shows shot in HD are recorded using higher-end formats.)

[edit] History

The HDV format was developed by JVC and Sony Corporation. The format was also initially supported by both Canon Inc. and Sharp Corporation. These four companies make up the HDV consortium as announced in September, 2003. All four companies are potential manufacturers of HDV hardware, but Sharp has not manufactured any HDV cameras at this time. HDV has since been supported by several other companies, including Apple, Avid, Canopus (now part of Grass Valley), Sony Media Software, and Ulead. In 2007 Constructive Lab developed a solution allowing HDV to be securely transmitted over low bandwidth networks.

JVC was the first to release an HDV camcorder, the GR-HD1, using a single 1/3" CCD sensor. With the GR-HD1, the user could select standard DV (480i) or HDV (720p30 or 480p60) modes, using the old 601 color space standard rather than the newer 709 standard. Due to this and other limitations the GR-HD1 did not gain widespread acceptance, and JVC later shifted their HDV development to shoulder-mounted cameras using their own extension of the HDV format called ProHD - which includes a native 720p shooting mode at 24 fps.

Sony was second to launch an HDV camcorder in September 2004: the Sony HDR-FX1. The FX1 has three 1/3" CCDs and was the first HDV camera to attract widespread interest, sparking a trend of affordable HD production which continues to gain momentum today. The FX1 records in HDV 1080i format using either 50 Hz or 60 Hz recording (but not both), depending on the TV standard in the released market. The subsequent Sony HVR-Z1U is similar to the FX1 but added XLR audio inputs plus 44 additional features, most notably a dual clock which supports both PAL and NTSC formats on a single camera. In mid 2005, Sony released a consumer-oriented HDV camcorder, the HDR-HC1. An advanced version of the HDR-HC1 with XLR audio, the Sony HVR-A1E, was released in September 2005. In 2006, Sony released the HDR-FX7, HDR-FX7E, HVR-V1U, and the HVR-V1E, which were the world's first 1080p camcorders in a small format. These cameras use 3 CMOS sensors rather than the CCDs used in previous HDV models. In 2006, Sony replaced the HDR-HC1 with the less-expensive HDR-HC3 with a slightly improved CMOS chip, but omits some features (such as external mic-in) of its predecessor. The Sony HDR-HC3 was later replaced by the HDR-HC5 which uses the same CMOS chip as the HC3, but with different hardware not too dissimilar to that of the HC3 with the exception of xvYCC recording. The Sony HDR-HC7 was introduced with a higher pixel count CMOS sensor and the re-introduction of the microphone input. Like the HC5, the HC7 can also record xvYCC. In August 2007, Sony introduced a shoulder-mount HDV camcorder called the HVR-HD1000U, which uses the same CMOS sensor as the HC7, and is basically a more professional version of the HC7. It has a lens similar in size to that of the HVR-Z1U or HVR-V1U.^[1]

In September 2005, Canon entered the HDV market with the Canon XL H1, a modular HDV camera system with three 1440x1080 1/3" CCDs, interchangeable lenses and HD-SDI output. 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 fixed-mount lens. Canon then introduced the Canon HV10 which is a compact, consumer-priced HDV camera with a 2.76 Megapixel CMOS sensor. In April 2007 Canon released the updated Canon HV20 which adds a 24p Progressive + film mode where the CMOS sensor captures 24 frames per second progressive but using telecine is taped in 60i to remain compatible with consumer level editing suites.

Other HDV cameras are sure to follow, and according to one video magazine survey HDV has become the most widely used HD recording format for independent video production.^{[citation needed]}

The 720p and 1080i flavors of HDV are often abbreviated as HDV1 and HDV2, respectively. This abbreviation is unofficial and is not mentioned in HDV consortium documents, but is commonly accepted.^[2]

[edit] Overview

HDV was designed to offer existing video production environments a cost-conscious upgrade path from standard-definition (SD) to high-definition (HD) video. As such, HDV shares the same DV25 cassette-media and tape-transport as DV. Recording times for HDV are identical to DV -- a 60 minute MiniDV cassette can store 60 minutes of either DV or HDV footage. As of yet, no HDV cameras can record HDV at LP speed, so the maximum record time on one tape is 80 minutes, as opposed to 120 with an 80 minute tape at LP. Although wanted by the consumer market, it is not likely that there will be an HDV camcorder that records HDV in LP mode because of the even higher risk of video drop outs on the thinner 80 minute tapes.

HDV recorders are offered to both the consumer and entry-level video production market. Consumer models are sold to the mass consumer market, competing with other camcorder product used for home, travel and vacation video. HDV video can be edited on a modern desktop/laptop PC, and burned and distributed on home-video DVDs. Prosumer models are designed for individuals and organizations specifically interested in video production, and are generally sold to amateur videographers, local production and marketing agencies, etc. HDV video can also be imported into a professional environment, although the quality of the product limits this use to news and other non-studio applications.

[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) -- compared to data rates of 50-100 Mbit/s and up for other HD formats.

Using MPEG-2 video enables HDV to achieve a higher compression ratio than recording formats without interframe compression, but at the cost of motion-induced artifacts in scenes of complex motion. The artifacts are a limitation of the compression technology and bitrate allocated to the video bitstream. Scenes with little motion are easier for HDV to compress than scenes with rapid movement, strobing lights, or other complex activity. For example, a scene of a moving riverbed may exhibit regions of picture breakup, depending on the amount of movement in the water. A static scene of a mountain countryside, by comparison, will exhibit none of these visual problems.

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 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 AG-HVX200 camera uses 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.

The BBC currently considers HDV marginal for broadcast purposes but accepts it in limited amounts for some programs. Their preferred choice of format for HD recording is currently HDCAM. They also accept HDV cameras for use in producing widescreen SD footage, with some caveats about how to do so. (For example see Alan Roberts' Z1E/FX1E analysis.) HDV was used in the primetime TV series "JAG" for some scenes where larger HD cameras would have been impractical, with successful results for complex scenes of sunlight over ocean water -- with both dark and light content in the subject matter.

Canon has started to ship HDV camcorders which are capable of 24 progressive frames per second. That is, 24 progressive 1080 frames are captured per second, each of which is stored as two coded fields in a 1080i bitstream. This allows decoders to display the progressive frames as full resolution 1080p frames at 24 frames per second or to use "2:3 pull-down" display to show it on a 60-field per second interlaced display.

HDV has some similarities to the more professional XDCAM-HD format, but the latter uses higher data rates for both video and audio signals.

[edit] Resolution and aspect ratio

In HDV, the video frame is defined to have an aspect ratio of 16:9. Permitted resolutions are 720p and 1080i.

HDV 720p uses a resolution of 1280x720 square pixels. HDV 1080i uses a resolution of 1440×1080 pixels, but is still displayed with an device aspect ratio of 16:9 This is because the pixel aspect ratio is 1.33:1 stretching the actual pixels to make the proper resolution. This means it has lower horizontal resolution than true 1080 HD formats (1920x1080), but the same applies also to most other widely used HD formats including XDCAM HD, DVCPRO HD and HDCAM, all of which have the same or lower resolution as HDV.

Device Aspect Ratio summary
NTSC/Pal 4:3
HD/HDV 16:9

Pixel Aspect Ratio summary
NTSC .9:1
NTSC Widescreen 1.2:1
HDV 720p 1:1
HDV 1080i/p 1.33:1
HD 1:1

Despite this, the perceived detail of HDV is much higher than that of PAL or NTSC DV formats. 1440 pixels is still twice the horizontal resolution of SD formats. In total, each HDV frame has 1,555,200 pixels, which is 4.5 times the resolution of NTSC DV (345,600 pixels) and 3.75 times that of PAL DV (414,720 pixels).

The numbers above refer to the luminance (brightness) information only; chrominance (color) information is subsampled (4:2:0 for HDV) to reduce the amount of data, as happens with DV and DVD, although NTSC DV uses a different sampling pattern (4:1:1). In other words, in all these formats, the chrominance resolution is one quarter of the luminance resolution. Most professional video formats use a 4:2:2 sampling pattern, and some high-end formats support 4:4:4, which is to say full chroma sampling.

[edit] Notes regarding specific camcorder models

Some Canon HDV cameras support pseudo progressive scan (which they denote by "F") in 1440x1080 resolution. They achieve this by doubling the horizontal scan rate to scan the interlaced sensor twice in one cycle. This lets them use a less expensive sensor at the expense of some interlacing artifacts. There will be fewer artifacts than 50i/60i, but the images will not be as detailed as true 25P/30P. Also, various practical tests have shown that resolution in 24F/25F/30F pseudo progressive modes is lower than when 50i/60i is selected. The exceptions to this are the Sony HVR-V1 and Canon HV20 camcorders which scan progressively in 1440x1080 resolution, and store the resultant data using either 2-3 pulldown (in 24p mode) or PsF (in 25p and 30p modes) techniques, so there's no resolution loss.

[edit] Editing HDV

As a consequence of the fact that HDV uses the interframe MPEG-2 GOP (group of pictures) structure instead of a solely intraframe compression system, native editing of HDV footage differs technically from the native editing of DV footage. In DV, frame-accurate splicing does not disturb the surrounding video because each frame of the video is stored as a self-contained unit. In HDV, splicing always introduces distortion at the splice points, due to the interdependencies between groups of video frames. Any editing of the video, whether it be a complex transition or a simple scene-change, requires a decompression and recompression of the entire HDV frame group. All modern professional non-linear editing software handles HDV by recompressing only in scenes where absolutely necessary, rather than needlessly recompressing the entire video. This limits degradation to the points of edit.

Editing HDV's native MPEG-2 transport stream files also forces the computer system to work much harder to perform even simple tasks of cutting and splicing as frames that do not actually exist as independent cells have to be re-built by the NLE system on-the-fly.

If HDV footage is converted (known as 'Transcoding') to a good intermediate format for editing, these considerations will not necessarily apply, and gradual degradation from generation to generation of edit may be avoided while substantial system performance gains are made. The lossy Apple Intermediate Codec (which runs out of QuickTime) is an efficient, easily usable codec for editing HDV in systems such as Final Cut Pro but lacks the transcoding and generational quality of some third-party HDV Intermediate codecs. CineForm's 'ConnectHD', 'AspectHD' and 'ProspectHD' intermediate codecs and encoding utilities not only maintain higher quality but also function within the rendering engine of some software editing systems (such as Premiere Pro) to boost real-time performance without hardware assistance. CineForm products currently work with Sony Vegas, Premiere Pro, and Corel's Ulead MediaStudio Pro 8 and Ulead Videostudio 11 Plus editing systems. Lumiere HD offers a similar functionality for Mac based editing systems (namely Final Cut Pro) but without any real-time assistance. BitJazz's SheerVideo offers lossless real-time codecs that speed editing with zero generational loss, although Final Cut Pro only supports camera manufacturer third-party codecs for real-time effects.

There are many advantages to editing HDV using a Lossless Intermediate rather than the native MPEG-2 file however the trade off for transcoding to a HDV Lossless Intermediate is that the file size is substantially increased and so large hard drive arrays are required for storage of footage. Avid Xpress Pro can edit using native HDV, and Avid also claims to have the advantage of being able to work with mixed formats in the timeline, without the need to transcode any material, since different formats are coped with seamlessly for viewing and output, with automatic conversion as required. Apple's Final Cut Studio also handles native HDV with realtime effects without any additional hardware and will mix it with other frame sizes as well as frame rates in the same sequence. It must be noted though that when DV material, for example, is included in an HDV project, a problem arises because it must be de-interlaced prior to scaling to the HDV format, and then re-interlaced. De-interlacing is generally regarded as a very difficult process to do well. This problem will arise of course in all editing software, regardless of whether a lossless intermediate format is used.

[edit] Interlaced Video Issues

For HDV cameras recording in interlaced formats there may be playback issues on some digital TVs and computers. Interlaced video has been criticized by many, but has been a useful compromise for decades due to its ability to display motion smoothly while reducing recording and transmission bandwidth.

HDV 1080i footage viewed on some plasma screens with interlaced display technology (e.g. ALiS) retains both sharpness and smooth motion while having less motion blur than typical movies. Hand-held material shot in progressive-scan mode can look jittery and confusing on such interlaced displays, probably due to an improper attempt to interlace what has been recorded progressively. Interlaced digital displays are not very common, however: recent sales trends increasingly favor progressive display technology such as LCD flat panels. Such displays use deinterlacing conversion processing for proper display of interlaced material.

Personal computers can also have problems playing interlaced video material, and the Windows Media Player may produce vertical ripples that appear to depend on the size of the output image and other factors.^{[citation needed]} Good deinterlacing can help solve this problem if the deinterlacing option is turned on, but deinterlacing high resolution video in real time requires appropriate video processing hardware.

One solution for preparing HDV source material for internet delivery is to encode it to a format like WMV-HD with deinterlacing during the encoding process. Some software can do this better than others, and the encoding time can be quite long depending on the output resolution and other factors. HDV source material yields excellent web video when properly encoded to WMV-HD or H.264 at bit rates of approximately 5-8 Mbit/s, as demonstrated on many HD demo sites.

Another solution to avoid deinterlacing is to shoot in 24p progressive mode. Some camcorders, including consumer-grade Canon HV20, provide an option to record 24p video within 60i stream, acting as a telecine machine. To achieve full 1080 lines of vertical resolution a display device or an editing system must be capable to recognize telecined video and to recombine full frames.

[edit] Alternatives

Since the introduction of HDV, other modestly priced HD recording options have been introduced as described below.

• Panasonic released the AG-HVX200 camera, which records in DVCPRO HD format at bit rates up to four times that of HDV on DVCPRO P2 cards or external hard-drive based recorders. This allows the HVX200 to offer better color depth and avoid inter-frame compression issues compared to HDV, but requires a significant investment in recording media and a careful archiving plan for preserving master footage (since the recording media is too expensive to use for archival purposes). The image clarity of the HVX200 is also limited by its sensor resolution of 960x540 pixels, compared to up to 1440x1080 for HDV.
• Panasonic also partnered with Sony to develop the AVCHD format, which uses H.264 encoding to compress high-definition video at bit rates similar to HDV with potentially higher quality. Some think AVCHD will eventually replace HDV for similar purposes, but for now HDV remains popular due to its cost-effectiveness and convenience.
• In late 2007 Sony plans to introduce the 'XDCAM EX' Cine-Alta HD camera, which will have three 1/2" CMOS sensors with full 1920x1080 resolution and can record at that resolution using XDCAM (MPEG2) compression at bit rates up to 35 Mbit/s. It will also have a dual auto/manual focusing system plus a full 720p LCD display, and a tapeless workflow using the new "SxS" memory card format co-developed by Sony and SanDisk. All of these features combine to make this a highly anticipated camera for professional video production.

For those requiring the highest possible HD quality there are other options available using a variety of high-bandwidth recording formats and cameras costing tens or hundreds of thousands of dollars. Some have suggested that HDV is not "true HD" by comparison, but it is a legitimate high-definition recording format and matches well with available HD delivery solutions.

[edit] Editing software support

See also Non-linear video editing

For Mac OS X:

• VLC Media Player, Free and opensource. Displays 24p without trying to interlace it like other decoders.
• Avid's Xpress Pro HD, Supports a wide range of HDV formats/standards, but no support for true 24p HDV.
• iMovie HD Universal binary, as of latest version (6.0.3), it does not support 24p HDV.
• Final Cut Express and Final Cut Pro 6 Latest version of FCP 6.0 does support direct HDV 24p, and 720/25p which is used in PAL countries (i.e. needed when working with a JVC Pro HD camera in 720/25p mode)
• Lumiere HD Lumière HD (beta) for Final Cut Pro 5. First available software to edit HDV on a Mac with QuickTime based Non Linear Editing systems. This is the only Mac based application (other than FCP) which allows for back to tape in HDV encoding (Including JVC's 24p ProHD). No universal binary is currently available, and is reportedly unstable under Rosetta on Intel Macintoshes.
• MPEG Streamclip 1.8 for Mac is a Universal Binary and supports automatic 3:2 pulldown (Converts 24p to 29.97), this program can only perform basic edits such as cutting, copying, pasting and trimming, but is available free of charge, and has excellent tools for exporting, demuxing and converting video, for example from HDV format (usually with the .m2t extension) to MPEG-2 (.mp2) format. MPEG Streamclip can handle most MPEG container formats (including ts, ps, vob, dat, mpg, and mp2) which adds to its usefulness.
• HDVxDV's [1] Now Universal Binary. This program loads in HDV (Including JVC's 24p ProHD) and transcodes to whichever format the user wishes to cut in. Timecode support is inaccurate. Does not allow for back to tape in HDV.

For Microsoft Windows:

• VLC Media Player, can display 24p properly, does not try to interlace like other decoders.
• NewTek SpeedEDIT, Supports all SD, HD and HDV resolutions/frame rates up to 2k film. Does not need an intermediate codec for real time editing. First software editor with real time full resolution/framerate 1394 HDV preview through camera or deck while editing. Can mix formats, resolutions and framerates in a single timeline. Well integrated timeline and storyboard interface.
• Avid's Xpress Pro HD,
• Avid's Liquid
• Adobe's Premiere Pro
• Adobe's Premiere Elements (from version 3.0 onward)
• Canopus' Edius
• Pinnacle Studio 11 Plus or Ultimate
• VirtualDub called VirtualDub-MPEG2
• Sony Media Software's Sony Vegas.
• Sony Media Software's Sony Vegas Movie Studio Platinum Edition.
• CineForm Aspect HD + Connect HD
• Avid Adrenaline HD + Xpress HD + Avid DS/Nitris
• Ulead MediaStudio pro 7, 8 and VideoStudio 9 and 10 Plus
• CyberLink PowerDirector
• MPEG Streamclip 1.0 for Windows, which has the same features as its Mac counterpart.
• MPEG Video Wizard DVD.
• Serif MoviePlus 5

Under Linux:

• Cinelerra - free software, allows HDV editing and composition
• Kdenlive is a non linear video editor, free software, based on the MLT video framework which relies on the FFMPEG project, thus providing support for various HD standards, including HDV.

[edit] Specifications

[edit] See also

• ProHD - a variant on HDV
• Digital cinematography
• Filmizing

[edit] References

1. ^ HVR-HD1000U Press Release (Sony).
2. ^ Editing HDV.

[edit] External links

• How DV Works at Videomaker.com
• Latest HDV camcorder reviews, news, and product information at DigitalCamcorderNews.com
• HDV Format Legal Information site
• Sony HDV Info
• German Forum with HDV focus
• HDV information: HDV FAQ

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