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HDV can also mean Hepatitis D virus. HDV is an inexpensive High-definition Video recording format which uses MPEG2 compression to fit high-definition 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.) HDV Camcorder ]] HISTORY The HDV format was developed by , Sharp Corporation , and Sony Corporation . These four companies make up the HDV consortium and are all manufacturers of HDV hardware. They announced their HDV partnership in September, 2003. Sharp has not manufactured an HDV camcorder at this time. They have since been joined by other companies, notably Avid, Canopus, Ulead, Sony Media Software, and Apple, Inc. 2007 Constructive Lab developed a solution allowing HDV to be securely transmitted over low bandwidth Intranets and Internet. JVC was the first to release an HDV camcorder, the GR-HD1. With the GR-HD1, the user could select standard DV (480i), or HDV ( 720p 30, 480p 60) mode. Sony was next to launch an HDV camcorder. Introduced in September 2004, the Sony HDR-FX1 recorded in HDV 1080i format. Depending on the TV standard in the released market, the unit would support either 50 Hz or 60 Hz recording (but not both.) The Sony HVR-Z1U , the equivalent U.S. professional model, supports both and adds XLR audio plus 44 additional features, most notably a dual clock that could support either 50 Hz or 60 Hz formats, allowing for both PAL and NTSC on a single camcorder. In 2005, Sony released the consumer-oriented HDV Camcorder, the HDR-HC1 . A professional version of the HDR-HC1, the Sony HVR-A1E , was released in September 2005. In 2006, Sony released the HDR-FX7 , HDR-FX7E, HVR-V1U, and the HVR-V1E, marking the world's first full 1080p camcorders in a small format, with both 24p and 30p (only 25p on the HVR-V1E) features on the camcorder (except for the HDR-FX7 and HDR-FX7E). JVC has developed its own extension of the HDV format called ProHD which shoots natively at 720p24. In September 2005, Canon entered the HDV market with the Canon XL H1 , a professional, modular HDV camera system, and in July of 2006, Canon announced their XH A1 and XH G1 models which are similar to the XL H1 but in a smaller form factor and a fixed-mount lens. In 2006, Sony appended the HDR-HC1 with the less-expensive HDR-HC3. The HDR-HC3 features a slightly improved CMOS chip, but omits some features (such as external mic-in) of its predecessor. Canon then introduced the + 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. 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. It has a lens similar in size to that of the HVR-Z1U or HVR-V1U. HVR-HD1000U Press Release (Sony) OVERVIEW HDV was designed to offer existing video production environments a cost-conscious upgrade path from standard-definition (SD) to high-definition (HD) video. Since HDV operates at the same recorded datarate (25 Mbit/s Bitstream Rate ) as DV, HDV recorders share the same physical ( MiniDV ) tape transport as existing DV equipment. For the camera, the main expense is concentrated in the optics and imaging electronics. Compared to HD video equipment built on more professional standards (such as HDCAM and DVCPRO HD), HDV enjoys a tremendous cost advantage. HDV camcorders open high-definition video acquisition to consumers, amateur videographers, and low-budget TV production. Although 1080i HDV and DV share the same (DV) tape format and the same recorded datarate, they use different video compression technology. The DV codec uses strictly an intraframe (spatial) scheme, whereas HDV uses the MPEG-2 video format, including both intraframe ( Spatial Compression ) and interframe ( Temporal Compression ) coding. This allows HDV to achieve its higher spatial resolution at the target bitrates of 19.7 Mbit/s (720p) and 25 Mbit/s (1080i). Compared to more expensive HDCAM and DVCPRO HD equipment, HDV suffers from significantly more spatial and temporal (motion) artifacts. As a consequence of interframe (temporal) compression, HDV editing is more complex, and introduces some editing distortion near splice points (due to the interdependencies between video frames). Compared to conventional SD DV, HDV offers much higher spatial resolution and higher overall fidelity, so most observers are willing to accept these problems. While standard definition MPEG-2 broadcasts typically use only 2 to 4 Mbit/s, the 25 Mbit/s of HDV enables both high-definition video storage and a lower degree of compression artifacts, with much less visible artifacts (although the more modern MPEG-4 / AVC or WMV-HD video coding formats could produce equally good HD results at substantially lower bit rates). HDV audio uses lossy compression ( MPEG-1 Layer 2 ) to reduce the audio bitrate to 384 kbit/s. DV audio uses uncompressed 16-bit PCM at 1536 kbit/s. As a result, HDV audio is technically inferior, although MPEG-1 at 384 kbit/s is regarded as 'perceptually lossless.' Canon has started to ship consumer camcorders that 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. Since HDV and DV use the same DV25 tape transport, at the same linear speed, recording times for DV and HDV are identical. That is, 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. Because HDV uses the same tape form factor as DV, users should be able to use any high quality MiniDV tape in their HDV camcorder. However, because HDV has a lower tolerance for drop-outs because of its long-GOP compression, many HDV users purchase either "master" quality Mini-DV tapes or specially formulated HDV tapes. HDV COMPRESSION Although HDV and DV share the same tape format and the same recorded datarate, they use completely different video compression technology. The DV codec is strictly an intraframe (spatial) compression. Each DV video frame is recorded as an independent picture, with a fixed bit allocation and uniform placement on the videotape. The HDV codec is based on MPEG-2 video compression, which employs both intraframe and interframe (temporal) techniques. Interframe compressors store only a fraction of the frames in a video as independent pictures -- called I frames -- and encode the remaining frames as changes relative to them. Consequently, HDV frames vary in size depending on their prior and future neighbors. In HDV 1080i, one in every 12 ( 25 FPS ) or 15 ( 30 FPS ) frames is an I frame. In HDV 1080p, one in every 12 (25 FPS) or 15 (24 or 30 FPS) frames is an I frame. In HDV 720p, one in every 6 (24, 25, or 30 FPS) or 12 (50 or 60 FPS) frames is an I frame. MPEG-2 video enables HDV to achieve a much higher compression ratio than DV, 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. Motion artifacts are imperceptible for static shots and gentle pans, but may become increasingly detracting as motion complexity increases. For example, a moving riverbed may exhibit regions of picture breakup, depending on its portion of the total screen area. It is important to view these limitations in the proper context. Lighting, chroma content, camera motion, etc all play a role in the potential for artifacts. The television series " JAG " shot many scenes using HDV without any incident, shooting over extreme latitudes of sunlight over ocean water, with dark and light content in the subject matter. For the DV codec to approach the spatial quality of HDV, it would require more than four times the storage space. Encoders are constantly improving; The Sony XDCAM HD format is very similar to HDV. MPEG is the standard of the future, and as encoders improve, the potential for artifacts lessens. Dropouts or errors in the compressed video bitstream affect HDV much more severely than DV. This is an unavoidable characteristic of interframe compression. Since frame data affects multiple frames (and not just the one it originated from), a dropout will impact all dependent neighbors. Frame-accurate editing is also made more difficult by the MPEG-2 codec. Any modifications to the video sequence require the surrounding group of frames to undergo a complete (and lossy) decompression/recompression cycle. However, virtually all professional non-linear editing software is now designed to work flawlessly with HDV. Currently the BBC considers HDV marginal for broadcast purposes but accepts it in limited amounts for some programs with prior consent. Their preferred choice of format for recording HD is currently HDCAM . They also accept HDV cameras for use in producing widescreen SD footage, with some caveats about how to approach doing so. (For example see Alan Roberts' Z1E/FX1E analysis. ) For all its limitations, HDV is quite stunning on HD displays. Although free of motion-induced artifacts, DV tends to look fuzzy when scaled up to HD resolutions. Subjectively, most observers are willing to accept HDV's visual artifacts in exchange for a more detailed picture. 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 aspect ratio of 16:9 (like SD widescreen formats, it uses a pixel aspect ratio of 1.33 instead of 1.0). 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. 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 , which is to say full chroma sampling. NOTES REGARDING SPECIFIC CAMCORDER MODELS Many HDV cameras support progressive scan (which they denote by "P"). 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 it will not be as smooth as true 25P/30P. Also, various practical tests have shown that resolution in 24P/25P/30P progressive modes is lower than when 1080i interlaced is selected. The exception to this are the Sony HVR-V1 camcorders which scan progressively and store the resultant data using either (in 24p mode) or PsF (in 25p and 30p modes) techniques, so there's no resolution loss. Prosumer HDV video camera. 24P]] XL-H1 HDV camera. Capable of 24f, 30f and 60i]] 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, as each frame of a video sequence is stored as an independent object, the recorded footage can be spliced at any frame without any loss of quality. When editing HDV's MPEG-2 data directly, a single frame cannot be changed without re-encoding subsequent frames from the same group. Any editing of the native MPEG-2 video, whether it be a complex transition or a simple scene-change, requires a decompression and recompression of the entire HDV frame group. Especially over many generations, this may result in increased artifacting, for example in the next frame group after a splice. However, because HDV's 1080i bitrate is 25 Mbit/s, these should be not as obvious as those seen when lower bitrates, such as those used for encoding clips for download, are used. 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 don't 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 and offers no realtime performance assistance. 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 does not yet support 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. 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. INTERLACED VIDEO ISSUES For HDV cameras recording in Interlace d 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 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. 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/sec, as demonstrated on many HD demo sites. ALTERNATIVES Since the introduction of HDV, other options have been developed to record high-definition video at modest prices compared to previous high-end solutions, as described below. - Panasonic introduced the AG-HVX200 camcorder, 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 master footage. (Since keeping footage on the P2 cards or hard drive recorders isn't economically practical.) - 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' video camera recording in the XDCAM HD format on a new solid-state media format calles 'SxS'. This camera will use MPEG2 compression like HDV but with a higher bit rate recording option, and offer a tapeless workflow like the Panasonic HVX200 with longer recording times and potentially lower cost for the memory cards. It will also have the largest imaging sensor of any HD camera under $10,000 and hence likely offer better low-light performance, an issue with all other HD cameras in this price range. - For those requiring the highest quality HD footage there are several advanced recording options available, in cameras costing tens of thousands of dollars or more. Some users of such cameras describe HDV as not being 'real HD,' but that's a vague statement which is difficult to define. HDV works well for the price, and this has helped make it one of the most popular HD recording formats yet developed. EDITING SOFTWARE SUPPORT See also Non-linear Video Editing For Mac OS X :
For Microsoft Windows :
Under Linux :
SPECIFICATIONS SEE ALSO
REFERENCES EXTERNAL LINKS
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