Category Archives: H

Hard disk drives

Hard disk drives (HDD) comprise an assembly stacking up to 12 (typically 5 or 7) rigid platters coated with magnetic oxide, each capable of storing data on both sides. Each recording surface has an associated read/write head, and any one may be activated at a given instant. Disk drives give rapid access to vast amounts of data, and are highly reliable as they have only two moving parts – the swinging head assembly and the spinning disk. They can be written and read millions of times. The use of disks to store audio, video and images has changed many aspects of digital production editing and transmission.

For high capacity, disks pack data very tightly indeed. Areal density, the amount of data stored per unit area of the disk surface, is one measure of their technology. Currently available high capacity drives from manufacturer Seagate achieve nearly 1 Tb/square inch in a 6 TB drive. Several new technologies are ready to boost the performance of future drives. These include filling the drive with Helium gas offering lower friction, so allowing more platters to be used in the same standard sized 3.5-inch case. Perpendicular magnetic recording (PMR – laying tracks under one another) is established technology. Upcoming techniques include shingled magnetic recording (SMR) and heat-assisted magnetic recording (HAMR). These create new spaces for yet greater capacities and performance of disk drives.

The rate of increase in capacity seems to have slowed in recent years which may mean that the currently used technology (PMR) is nearing its practical limit. For this performance the heads float only a few molecules off the disk surface, so that even minute imperfections in the surface can cause heating of the head assembly. As a result, high capacity disk drives have to be handled with great care, especially when running. Vibration could easily send heads off-track or crashing into the disk surface – possibly with terminal consequences.

Where will hard disk drives be in 10 years’ time? In 2000, when 50 GB was ‘high capacity’, the Digital Fact Book successfully predicted the arrival of 2TB drives in 2010. Now a new 10-year prediction is made. The long term historic HDD storage development doubles the capacity every two years (increasing 41%/year). In some years it has reached 60%, but the DFB believes progress is getting tougher and expects progress to be nearer 41%/year. Anyway, who wants a 660 TB HDD – perhaps someone working with 8K UHD at 120 f/s?

HDD capacity chart























See also: Areal Density, RAID, SCSI



Hybrid Broadband Broadcast TV (HbbTV) is a European initiative to provide both broadcast and broadband/web content on viewers’ screens. It combines linear (normal) channels with internet content, providing interactivity and the ability to deliver service packages to all relevant devices.

Differences in viewing between computer and TV do not help, such as viewing distance: lean forward (PC) and lean back (TV), lack of mouse and keyboard on TVs, different colors: PC black text on white – the reverse on TV, and lack of computing power in TVs.

See also: Second screen


A D5 VTR (1994) adapted to handle high definition signals. Using around 5:1 compression the signals connect via an HD-SDI link. HD D5 can be multi-format, operating at both SD and HD TV standards. It can replay 525-line D5 as well as HD D5 cassettes. Formats include 480/60I, 1080/24P, 1080/60I, 1080/50I, 1035/59.94I and 720/60P. The recorder can also slew between 24 and 25 Hz frame rates for PAL program duplication from a 1080/24P master.

Cassette recording times vary according to format, the longest is 155 minutes for 1080/24P.



Designed as the successor to the standard DVD optical disk and principally supported by Toshiba, HD DVD could store about three times as much data as its predecessor; 15 GB single layer, 30 GB dual layer. Often called 3x DVD as it has three times the bandwidth (1x@36Mb/s and 2x@72Mb/s) and storage, it was discontinued in 2008, leaving just Sony’s Blu-ray Disc in the market.

See also: DVD, Optical disks


HD ready

This describes a television that can display the recognized 720 and 1080-line formats but does not include the tuner or decoder needed to receive the signals. Typically the screen will not have the full 1080-line resolution so such video will be up-res’d.


This refers to HDTV signals in RGB form rather than Y,Cr,Cb form. The difference is that HD RGB is a 4:4:4 signal that can carry the full bandwidth of each of the R, G and B channels, whereas HD (TV) is normally considered to be in 4:2:2 form where the color difference signals have a more restricted bandwidth. Generally, the 4:2:2 form of HD is sufficient for most television applications and can be carried in its uncompressed form by a single SDI connection. HD RGB is often used for critical keying shots for television, and for digital cinematography. The availability of a suitable recorder makes working with the format generally more affordable.


Also known as D11, this series of Sony VTRs, introduced in 1997, was based on the Betacam principles for recording HD video on a tape format which uses the same style of cassette shell as Digital Betacam, although with a different tape formulation. The technology supports 1080-line standards. Various methods are used to reduce the video data including pre-filtering, DCT-based intra-frame compression and sampling at around 3:1:1. Together these provide data reduction of between 7 and 10:1. Four non-compressed audio channels sampled at 48 kHz, 20 bits per sample, are also supported. One variation, CineAlta, is aimed at addressing the needs of digital cinematography.

HDCAM SR, introduced in 2003, was a further extension of Betacam recorders using mild MPEG-4 Studio Profile (SP) intra-frame compression to store full bandwidth 4:4:4 HD RGB 1080- and 720-line video offering more headroom for digital cinema users, as well as 4:2:2 Y,Pr,Pb component video for television. It offers video data rates of 440 Mb/s and 880 Mb/s, and more audio channels. It can cover SD, HD and film-resolution data (10 or 12 bit), and color resolution (component or RGB). The Sony F950 camera provided suitable RGB sources for HDCAM SR, including undercranked (shooting at a lower than normal framerate) footage. The close-to-raw-state of RGB material is suited to the needs of digital cinematography as the full latitude and bandwidth of the pictures is preserved through recording.

See also: 24PsF, CineAlta, D11



High-bandwidth Digital Content Protection was designed by Intel to stop any copying of digital video while it is being transported across DVI or HDMI interfaces. This means it eliminates the possibility of intercepting digital data midstream between the source (set-top box, DVD players, etc,) and the display screen. HDCP, which encrypts the digital data, is also used in digital cinema. In all cases it is used to protect all high resolution (HD, UHD and Digital Cinema) content from being copied on the link from player to screen.

See also: HDMI



The High-Definition Multimedia Interface is a digital audio and video interface able to transmit uncompressed streams. It is used in both consumer and professional devices from television sets, to set-top boxes, camcorders, to games consoles, Blu-ray Disc players… and more. It replaces a big pile of lumpy analog connections such as SCART, composite video, as well as DVI, audio and more. In 2013, 10 years after the specification was released, over 3 billion HDMI devices had been sold.

Type A standard 19-pin – very widely used.
Type B 29-pin not used yet but ready for large video formats such as WQUXGA (3,840×2,400).
Type C is a mini version of Type A, intended for mobile devices.
Type D is a micro version, even smaller than Type C.
Type E is the Automotive version with a locking tab and a shell to keep water out.

The Version 1.1 specification supports a maximum pixel clock rate of 165 MHz, sufficient for1080/60P and WUXGA (1920×1200) and 8-channel 192 kHz 24-bit audio as well as compressed streams such as Dolby Digital. The current HDMI 1.3 offers 340 MHz capability – beyond WQSXGA (3200 x 2048) – and offers future proofing.

The data carried on HDMI is encrypted using High-bandwidth Digital Content Protection (HDCP) digital rights management technology – meaning that the receiving end needs to be able to decrypt HDCP.


High Dynamic Range (Imaging) techniques allow a greater dynamic range of exposure (stops) than normally possible, with the intention of accurately representing the wide brightness range of real scenes ranging from direct sunlight to deep shadows. This is sometimes used with computer-generated images or photography (often by taking several pictures of a scene, each with a different exposure setting) and it can provide a large amount of headroom for the adjustment of images in post production.

HDR can have a significant effect on the viewer experience. Some consider it as the best achievable next step beyond the normal experience of HD – placing it above 4K and HFR.


High Definition Television. A television format with higher definition than SDTV. While DTV at 625 (576) or 525 (480) lines is usually superior to analog PAL and NTSC, it is generally accepted that 720-line and upward is HD. This also has a picture aspect ratio of 16:9.

While there are many picture HDTV formats there is a consensus that 1920 x 1080 is a practical standard for global exchange of television material; a common image format. Many productions are made in this format.

See also: 24P, ATSC, Common Image Format, DVB, Table 3


High definition DV is a tape format that stores long GOP MPEG-2 encoded HD video onto DV or MiniDV tape cassettes. There are two standards. One is 1280 x 720 lines at 60, 50, 30 and 25P frame rates with a target compressed video rate of 19 Mb/s. The other is 1440 x 1080 lines at 50 and 60I interlaced vertical rate with a target bit rate of 25 Mb/s. All video sampling is 8-bit 4:2:0, 16:9 aspect ratio so the 1080-line format does not use square pixels. Audio is two channels of 48 kHz, 16-bit and uses MPEG-1 Layer 2 compression producing 384 kb/s total.

At its introduction in 2004, HDV represented a huge price drop for HD camcorders. However the quality is ‘prosumer’ but it opened up a new layer of operations for HD. Also the SD downconverted output is better than the usual SD DV results. The use of long GOP coding impedes frame-accurate editing.

See also: AVC-Intra


HEVC is a new generation of High Efficiency Video Codecs that are used to reduce the bandwidth needed specifically to support 4K and 8K UHDTV video programming. It is hoped this will be up to 50% more efficient than MPEG-4.

See also: Display Resolution


A numbering system, often referred to as ‘Hex’, that works to base 16 (instead of our usual base 10) and is particularly useful as a shorthand method for describing binary numbers. Decimal 0-9 are the same as Hex, then 10 is A, 11 is B, up to 15 which is F.


See also: Binary


High Frame Rate – a frame rate higher than normal. For instance, movies (films) are normally shot at 24 f/s but some have been shot at 48 f/s – HFR. Some audiences say they do not like it as it’s too real and does not look like film.

It has been observed that when viewing UHD, motion judder is often very apparent and so a higher frame rate (say 48 f/s) is recommended by some. When shooting fast-action sports, such as football, then the UHD result would look better using, say, 50 or 60 f/s. In fact the UHD standard Rec 2020 includes frame rates up to 120 f/s.

High Speed Camera Systems

It has been standard practice from the early days of film to shoot film at a higher rate, over-cranking, then it will be played back at normal speed to produce a slow-motion effect of high quality. However there was a limit to the speed at which film can be run through the camera. Many complex designs for film transports have been tried but they are limited to around 400 frames per second depending on film size and framing. Early uses in military applications were picked up by the creative community for dramatic effect.

Electronic imaging systems do not have the issues of moving a mass of film past the lens and once the problems of high speed digitization and storage were solved it allowed imaging up to 1,000,000 frames a second at low resolution. Most modern cameras are capable of some over-cranking to a few hundred frames per second and from there specialist cameras are available to cover high resolution and speeds of several thousand frames/second.


High performance parallel interface (ANSI X3.283-1996). Capable of transfers up to 200 MB/s (800 with the 6400 Mb/s HIPPI, a.k.a. GSN) it was targeted at high performance computing and optimized for applications involving streaming large volumes of data rather than bursty network activity. The parallel connection is limited to short distance and so Serial HIPPI is now available.This is now a largely obsolete technology being replaced by optical fiber and high performance network architectures.

See also: GSN

History (editing)

A Quantel term describing the ability to instantly recall original material in uncommitted form along with the associated editing data. This allows any late changes to be made quickly and easily. For example, a shadow could be softened or moved in a multi-layered commercial without having to manually find the original material or recalling the set-up data. Archiving a program containing History means that the operator no longer needs to remember to save packs or set-ups associated with the job as all the material and set-ups will be automatically included within the history archive.


High-Speed Downlink Packet Access is an enhanced 3G mobile telephone communications protocol. Also dubbed 3.5G, 3G+, and Turbo 3G, HSDPA allows networks based on the Universal Mobile Telecommunications System (UMTS) to offer enhanced down-link data rates up to 99.3 Mb/s. The more recent HSPA+ (High-Speed Packet Access) can achieve speeds of 337.5 Mb/s. The high-speed down-link data channel from the base station is shared between its mobile users, and constantly re-scheduled according to the quality of the radio link to each phone. The data speeds made available the delivery of good quality live video to mobile phones.


Hierarchical Storage Management is a scheme responsible for the movement of files between archive and the other storage systems that make up hierarchical storage architecture. Typically there may be three layers of storage, online, near-line and offline, that make up the hierarchy that HSM manages. Managing these layers helps to run the archive and have the required speed of access to all stored material.


HyperText Transfer Protocol provides the basis for data communication in the World Wide Web. It defines how messages are formatted and transmitted, and how web servers and browsers respond to commands. So a web address (URL) entered in a browser sends an HTTP command to a web server that then requests fetching and sending the page found at that URL.

See also: DASH

HTTP Live Streaming (HLS)

This HTTP-based media streaming protocol enables live streaming of audio or video over the internet for appropriate Apple products. It is a part of iOS, OS X, QuickTime and Safari and works by dividing the required source media into small chunks of around two seconds, then offering media files in several levels of H.264 video and MP3 or HE-AAC audio compression, providing from low to high bit-rate (and quality) delivered in an MPEG-2 Transport Stream. The data delivery system is adaptive to allow for variations of available data speeds, with the receiving end able to choose the highest bit-rate files it can receive fast enough to maintain live operation.

See also: Buffering, Adaptive bit-rate streaming

Huffman coding

This compresses data by assigning short codes to frequently occurring long sequences and longer ones to those that are less frequent. Assignments are held in a Huffman Table. Huffman coding is lossless and is used in video compression systems where it can contribute up to a 2:1 reduction in data.

See also: JPEG

Hyperstereo (Stereoscopic)

Using widely spaced cameras (e.g. beyond 70mm interaxial) which record more stereo effect than the eyes can see. Such a large interaxial distance can produce the effect of miniaturization. Also used in order to achieve the effect of more stereo depth and less scale in a scene.

For stereo effects on very long shots (e.g. landscapes) interaxial camera set ups of several meters have been used (hyperstereo). One extreme example of hyperstereo is from cameras on each side of the earth to record the sun in 3D.

See also: Miniaturization, Interocular, Interaxial

Hypostereo (Stereoscopic)

Using closely spaced cameras (e.g. less than 50 mm interaxial) which record less stereo effect than the eyes can see. Such a small interaxial distance can produce the effect of gigantism. If standard cameras are used, the minimum interaxial distance is typically limited by the thickness of the cameras, so a mirror or beam splitter system is often used, enabling interaxials down to millimeters.

See also: Gigantism