Tag : Files

Archive

Long-term storage of information. Pictures, sound and metadata stored in digital form can be archived and recovered without loss or distortion. The storage medium must be both reliable and stable and, as large quantities of information need to be stored, low cost is of major importance. Currently many are using magnetic tape. However there is also ongoing use of optical disks including DVD and Blu-Ray Disc formats and further developments are emerging.

Today, the increasingly IP and Ethernet-connected environments involving many video formats, including digital film, mean that data recorders make good sense. Archiving systems built around the current LTO-5 and LTO-6 data recorders are increasingly proving to be efficient and effective for media applications. The formats include backward compatibility to the previous LTO type. And with the tape cartridges offering 1.5 and 2.5 TB for LTO-5 and LTO-6 respectively, there is useful capacity.

Removable CD-size optical discs potentially offer quick access and denser storage as well as long-term reliability. The Archival Disc system, expected in 2015 from Sony and Panasonic, offers 300 GB with a roadmap to 1TB storage per disc.

For archiving stills and graphics there is far less need for of strong compression as the volume of data will typically be much smaller than that for video. CDs and DVDs are convenient and robust, giving near instant access to all stored pictures.

Traditionally, material is archived after its initial use – at the end of the process. More recently some archiving has moved to the beginning, or even before, the production process. An example is news where, in some cases, new material is archived as events happen. Later subsequent editing, etc., accesses this.

With the worldwide expansion of television channels everywhere, including online and mobile services, archives are increasingly used to help fulfill the huge demand for programming.

See also: AAF, Data recorders, LTO, Optical disks

AVC-Intra

A family of two HD codecs from Panasonic that were designed to be compliant with H.264/MPEG-4 AVC, and use only intra-frame coding (GOP of 1), making the coded material easily editable at every frame. AVC-Intra was aimed at professional users and was adopted by Panasonic for its P2 cameras (AVC-Intra P2), offering considerably more efficient compression than the original DVCPRO HD codec – maybe by as much as 2:1. This was at a time when long GOP coding was being used in products including HDV and XDCAM HD. With increased coding efficiency some believed the use of long GOP coding in professional recorders would fade.

There are two classes: AVC-Intra 50 and AVC-100. The former produces a nominal 50 Mb/s for 1920 x1080 and 1280×720 formats using 4:2:0 10-bit sampling, with the frames horizontally reduced to 0.75 of the original line length. AVC-100 produces up to 100 Mb/s with 4:2:2 sampling for the same two frame formats, but without any size reduction. Both codecs offer a range of popular framerates. Both these codecs are now included in Panasonic’s AVC-Ultra range.

 

 

See also: DVCPRO P2, MPEG-4, XAVC

Website: www.avchd-info.org

AVCHD

Advanced Video Codec High Definition, a joint development between Panasonic and Sony, applies MPEG-4’s AVC video coding and Dolby Digital (AC-3) or linear PCM audio coding, to meet the needs of the high definition consumer market with 1080i and 720p formats. The use of AVC provides at least twice the efficiency of MPEG-2 coding, used in HDV and MiniDV, to offer longer recording times or better pictures – or both. Possible recording media include standard DVD disks, flash memory and hard drives.

Further developments have expanded the applications of AVCHD technology. The AVCHD Format Version 2.0 adds specifications for 3D and 1080/60P and 50P and supporting trademarks; AVCHD 3D, AVCHD Progressive and AVCHD 3D/Progressive.

AVI (.avi)

Audio Video Interleave, a Microsoft multimedia container format introduced in 1992 as part of its Video for Windows technology. AVI files can hold audio and video data in a standard container and provide synchronous video/audio replay. Most AVI files also use the OpenDML file format extensions, forming AVI 2.0 files.

Some consider AVI outdated, as there are significant overheads using it with popular MPEG-4 codecs that seemingly unduly increase file sizes. Despite that, it remains popular among file-sharing communities, probably due to its high compatibility with existing video editing and playback software, such as Windows Media Player.

CIFS

Common Internet File System is a platform-independent file-sharing system that supports rich, collaborative applications over the internet which could be useful for collaborative post production workflows. It defines a standard remote file-system access protocol, enabling groups of users to work together and share documents via the Internet or within intranets. CIFS is an open, cross-platform technology based on native file-sharing protocols in Windows and other popular PC operating systems, and is supported on other platforms, so users can open and share remote files on the Internet without installing new software or changing work methods.

CIFS allows multiple clients to access and update the same file, while preventing conflicts by using sophisticated file-sharing and locking semantics. These mechanisms also permit aggressive caching and read-ahead/write-behind without loss of cache coherency.

CIFS also supports fault tolerance in the face of network and server failures.

In Quantel’s Genetic Engineering teamworking infrastructure, the Sam data server virtualizes media on-the-fly to give third-party applications instant access to all stored media using the CIFS protocol for no-API, out-of-the-box connectivity.

Website: www.microsoft.com/mind/1196/cifs.asp

Cineon (file)

An RGB bitmap file format (extension .cin) developed by Kodak and widely used for storing and transferring digitized film images in production and post production. It accommodates a range of film frame sizes up to full Vista Vision (rarely used format 36 x 18.3mm frame laid horizontally). In all cases the digital pictures have square pixels and use 10-bit log sampling. The sampling is scaled so that each of the code values from 0-1023 represents a density difference of 0.002 – describing a total density range of 2.046, equivalent to an exposure range of around 2,570:1 or about 11.3 stops. Note that this is no longer beyond the range of modern negative film and so has led to the use of higher precision file formats.

The format was partly designed to hold virtually all the useful information contained in negatives and so create a useful ‘digital negative’ suitable as a source for post production processing and creating a digital master of a whole program.

See also: 10-bit log, ACES, Color spaces, DPX

Codec

Originally short for a combination of a coder and decoder but now often used to describe just one or the other. Mostly codec refers to a compression coder or decoder such as JPEG, MPEG or JPEG 2000.

Compression ratio

The ratio of the amount of data in the non-compressed digital video signal to the compressed version. Modern compression techniques start with component television signals but a variety of sampling systems are used, 4:2:2 (‘Studio’ MPEG-2), 4:2:0 (MPEG-2), 4:1:1 (NTSC, DVCPRO), etc. The compression ratio should not be used as the only means to assess the quality of a compressed signal. For a given technique, greater compression can be expected to result in lower picture quality, but different techniques give widely differing quality of results for the same compression ratio. The more modern technologies, MPEG-4, (H 264), VC-1, JPEG 2000 and the latest HEVC (H.265), are more efficient than MPEG-2. The only sure method of judgment is to make a very close inspection of the resulting pictures – where appropriate, re-assessing their quality after onward video processing.

See also: Concatenation, DV, ETSI, JPEG, JPEG 2000, MPEG

Compression (video)

The process of reducing the bandwidth or data rate required to transport a video or audio stream. The old analog broadcast standards, PAL, NTSC and SECAM are, in fact, compression systems which greatly reduce the information that was present in the original RGB sources.

Digital compression systems analyze their sources, such as pictures and sound, to find and remove redundancy both within the signal. Some of the techniques were primarily developed for digital data transmission but have been adopted as a means of reducing broadcast transmission bandwidths and storage requirements on disks and VTRs.

A number of compression systems are in regular use for moving images. These include ETSI, JPEG, Motion JPEG, JPEG 2000, DV, MPEG-1, MPEG-2, MPEG-4, AVC, H.264, Windows Media, Real and many more. Where different techniques are used in the same workflow, quality problems can occur and picture quality/ audio can suffer more than if the same method is used throughout.

The MPEG-2 family of compression schemes, which was originally designed for program transmission, has been adapted for studio use in Betacam SX and IMX recorders.
While there is much debate, and new technologies continue to be developed, it remains true that the best compressed results are produced from the highest quality source pictures. Poor quality inputs do not compress well. Noise, which may be interpreted as important picture detail, is the enemy of compression.

The need for ever more efficient compression systems is partly driven by the bigger TV picture formats, HD images are about five times the area of SD. More recently UHDTV-1 (4K) and UHDTV-2 (8K), respectively are 4 and 16 times the picture area of 1920 x 1080 HD. New HEVC / H.265 coding is expected to be twice as efficient as MPEG-4, which is already twice as efficient as MPEG-2. This efficiency combined with the twice-as-efficient DVB-T2 and DVB-S2, together mean that 32 SD channels can now broadcast in the space that used to carry one anaolg TV channel. It also means that the channel could carry one 4K TV channel.

See also: Compression ratio, Concatenation, Digital Betacam, ETSI, HEVC, JPEG, JPEG 2000, MPEG-2, MPEG-4, Windows Media

Constant bit rate (CBR) compression

Compression systems that are used to create a fixed rate of output data. This is usually to fit within a given bandwidth such as that available on a video tape recorder or a constant bit rate transmission channel. With video, the amount of useful information contained in the material varies widely both spatially and temporally – with movement. For example, a football match with crowds and grass texture as well as fast panning cameras typically contains far more information than a largely static head-and-shoulders shot of a newsreader. Using constant bit rate means that the video quality may suffer in order to meet a specified maximum bit rate. In the football case, the texture of the grass may go ‘flat’ during a camera pan, and reappear when the camera is still.

As overflowing the available bit rate budget could have disastrous results with bits being lost, the aim is always to use just under the available bit rate. The degree of success in almost filling the available space (not easily done live) is a measure of the quality and efficiency of the compression system.

See also: Variable bit rate

COTS

Commercial off-the-shelf, usually referring to the use of common components from the computer market to create a product, or application. For instance COTS components and say, a Windows platform, can be used to make a channel-in-a-box integrated video playout system that replaces a host of dedicated hardware. Typically, to meet broadcasters’ expectations of reliability and performance, considerable attention to the precise choice of platform (not all computers are the same) along with considerable software development and testing is needed. The use of COTS in television and movie production is now commonplace. High end editing runs on COTS-based platforms, with the big development effort in software, not hardware!

DASH

Dynamic Adaptive Streaming over HTTP, A.K.A. MPEG-DASH, makes use of standard HTTP (Hypertext Transfer Protocol – as in the internet) web servers to provide a high quality adaptive bit-rate streaming video service. As the video or audio is usually quite long, and a lot of data, it divides the content into small segments which are then sent as a series of small HTTP files. The server makes the content available in a range of bit rates so the receiver can select the highest quality version that provides continuous video or audio – no freezes or breaks. It also means that the service can adapt to fit with the available bandwidth as the speed of the internet connection varies.

DASH-IF is the DASH Industry Forum that is made up of 67 industry members from around the world.

DASH-PG is the Promoters’ Group. Its membership includes manufacturers, content owners, operators, and more. The goal is to promote DASH as a widely available solution for adaptive streaming.

DASH-VLC a Video LAN Player designed to work with DASH. Generally VLCs are available as downloads, and can play a wide range of video formats. A DASH-VLC is designed to work with DASH.

Website: dashif.org

Data carousel

This is a file system that rotates and delivers its content into a network at a defined point in a cycle, for example, teletext pages. It is a method to make a large amount of information or data files available within a reasonably short time following a request. The data is inserted into the digital broadcast transport stream.

See also: IP over DVB

DFS

Distributed File System. Used to build a hierarchical view of multiple file servers and shared files on a network. Instead of having to think of a specific machine name for each set of files, users only need to remember one name as the key to a list of shared files on multiple servers. DFS can route a client to the closest available file server and can also be installed on a cluster for even better performance and reliability. Medium-to-large sized organizations are most likely to benefit from using DFS while smaller ones should be fine with ordinary file servers.

DivX

A video codec created by DivX, Inc. which can compress long video segments into relatively small data spaces while maintaining reasonable picture quality. It uses MPEG-4/H.264 or AVC compression to balance quality against file size, and is commonly associated with transferring DVD audio and video to hard disks.

DNxHD

Avid’s Digital Nonlinear Extensible High Definition codec with intra-frame compression is designed for multi-generation compositing with reduced storage and bandwidth requirements. It has four levels to match quality requirements and manageable data volumes. 145 or 220 Mb/s 8-bit and 220 Mb/s 10-bit all at 4:2:2. There is also a 36 Mb/s version for HD offline. This offers HD post at SD data rates, or less, meaning that infrastructure and storage requirements can be as for uncompressed SD. DNxHD is assigned as VC-3 by SMPTE.

Website: www.avid.com/dnxhd

Encryption

The process of coding data so that a specific code or key is required to restore the original data. In conditional access broadcasts this is used to make transmissions secure from unauthorized reception and is found on satellite, cable and terrestrial broadcast systems. Encryption and content security are vital to the growth of digital media markets where copies can be perfect clones of the owners’ valuable assets.

Entry point

A point in a coded video bit stream from which a complete picture can be decoded without first having to store data from earlier pictures. In the MPEG-2 frame sequence this can only be at an I-frame, the only frames encoded with no reference to others.

ETSI compression

A compression technique, based on DCT. Unlike MPEG, which is asymmetrical having complex coders and simpler decoders and is designed for broadcast, this is symmetrical with the same processing power at the coder and decoder. It is designed for applications where there are only a few recipients, such as contribution links and feeds to cable head ends. ETSI compression is intra-frame, simpler than MPEG and imposes less delay in the signal path, typically 120 milliseconds against around a second, enabling interviews to be conducted over satellite links without unwarranted delays. Data rate is 34 Mb/s.

FAN

File Area Networks are a shared storage concept that stores shared files in multiple locations. However the user is not aware of where the files are located; they are simply accessed as if they were local or single site storage. The IT industry is actively pursuing this concept in order to provide organizations with strategically central data sources that are geographically agnostic, which can lead to considerable resource savings.

FANs also have potentially broad applications in post production and broadcast. It is not impossible to imagine a post house with a ‘front door’ in the city where clients can come and watch their job progress, driven by a creative at in his country retreat – perhaps with the storage itself in a third location. Broadcasters with multiple sites (perhaps local stations or subsidiaries) are also looking at FANs with great interest.

Website: http://en.wikipedia.org/wiki/File_Area_Network

File-based (media)

‘File-based’ generally refers to storing media in files rather than as continuous streams like video tape. The term is more widely used to describe IT-based environments for handling and processing digital media. Media production is increasingly becoming file-based.

File transfer

A discontinuous transfer process which treats each transferred item as a single block, neither divisible into smaller, independent elements nor part of a larger whole. As the transfer process has a recognizable beginning and end (unlike streaming) it is possible for the complete transfer to be checked and any errors corrected. This is not possible with a streaming process.

File transfer requires material to be complete and clearly identifiable. When handling time-based material, such as video and audio, the complete file has to be available before transfer can start. If the whole clip is a single file, this cannot be transferred until all the material is complete. However, if the clip is sub-divided, for example into frames, the transfer can start immediately after the first frame is completed. This becomes important in time sensitive applications such the live editing of highlights while the event is still taking place.

See also: Streaming

FTP

File Transfer Protocol. The high level Internet standard protocol for transferring files from one machine to another. FTP is usually implemented at the application level.

See also: FXP

FXP

File eXchange Protocol uses FTP to transfer data directly from one remote server to another. This inter-server exchange operates without the data being routed to the client. Whereas normal FTP involves data transfers only between a client and a server, using FXP involves the client using an FTP connection to the two servers to command the data transfer. This can be particularly useful when moving large files, such as video, as it is only the connection between the two servers that needs to be fast; the client’s command operation requires only low bandwidth.

HEVC

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

HSM

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.

HTTP

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

I-frame only (a.k.a. I-only)

Video compression schemes in which every frame is intra-frame (I-frames) compressed, i.e. individually defined and does not depend on any other frames for decoding. There are no P (predictive) or B (bi-directional) frames in such compression schemes. This is considered preferable for studio use as edits can be made on any frame boundaries without involving any processing beyond decoding the individual frames.

All DV compression is I-frame only. MPEG-2 and MPEG-4 with a GOP of 1 is I-frame only. For example these are used in Sony’s IMX VTRs and HDCAM SR respectively. JPEG 2000 as used in DCI cinema is I-frame only.

See also: Cut (edit), D11, GOP, Intra-frame (compression), JPEG 2000, MPEG-2, MPEG-4

IEEE 1394a/b (a.k.a. FireWire, I-Link)

Developed by Apple and produced since 1994, it is a standard for a peer-to-peer serial digital interface which can operate at 400 to 3200 Mb/s (1394b) typically over shielded twisted pair cable up to 4.5m, and 100m on optical fiber.

Practically it can send A/V media over 100m of Cat-5 cable at 100 Mb/s. Consumers connect DV devices over longer distances using readily available low cost cables. IEEE 1394c has a data rate to 800 Mb/s over Cat5 cable and combines 1394 and GigE on one cable.

The high speed and low cost of IEEE 1394a makes it popular in multimedia and digital video applications. Uses include peer-to-peer connections for digital dub editing between camcorders, as well as interfacing video recorders, printers, PCs, TVs and digital cameras.

IEEE 1394 is recognized by SMPTE and EBU as a networking technology for transport of packetized video and audio. Its isochronous data channel can provide guaranteed bandwidth for frame-accurate realtime (and faster) transfers of video and audio while its asynchronous mode can carry metadata and support I/P. Both modes may be run simultaneously.

IEEE 1394 is known as FireWire by Apple, I-Link by Sony and Lynx by Texas Instruments. Future developments of FireWire are expected to increase data speed to 6.4 Gb/s.

See also: Asynchronous, Isochronous

Website: www.1394ta.org

IEEE 1588

This describes a Precision Time Protocol (PTP) that enables synchronizing distributed clocks to within 1 microsecond via Ethernet networks with relatively low demands on local clocks, the network and computing capacity. There are many applications for example in automation to synchronize elements of a production line (without timing belts).

PTP runs on IP networks, transferring precision time to slave devices via a 1 GHz virtual clock (timebase). Independent masters can be locked to one master clock, creating wide, or even global locking. SMPTE has been assessing the possibilities of using PTP as a synchronizing source for television applications.

 

See also: Black and burst, Tri-level sync

Inter-frame (compression)

Video compression which involves more than one frame to code and decode. Inter-frame compression compares consecutive frames to remove common elements and arrive at ‘difference’ information to describe the frames between the (integral) I-frames. MPEG-2 and MPEG-4 use two types of inter-frame processed pictures – the ‘P’ (predictive) and ‘B’ (bi-directional) frames. As ‘P’ and ‘B’ frames are not complete in themselves but relate to other adjacent frames, they cannot be edited independently.

See also: Cut edit, I-frame, MPEG-2, MPEG-4

Intra-frame (compression)

Compression that uses just one picture. The compression process only is designed to remove what it considers to be redundant and visually less significant information from within the frame itself. No account is taken of other frames. JPEG and the ‘I’ frames of MPEG-2 are coded in this way and use DCT. In an MPEG-2 sequence of frames editing can only be at I-frames as they are the only independent frames.

 

See also: DCT, I-frame only, JPEG, MPEG-2

Isochronous

A form of data transfer that carries timing information with the data. Data is specified to arrive over a time window, but not at any specific rate within that time. ATM, IEEE 1394 and Fibre Channel can provide isochronous operation where links can be booked to provide specified transfer performance. For example, 60 TV fields can be specified for every second but their arrival may not be evenly spread through the period. As this is a guaranteed transfer it can be used for ‘live’ video but is relatively expensive on resources.

See: ATM, Asynchronous, Fibre Channel, IEEE 1394, Synchronous

JPEG 2000 (.JP2)

This is another image compression system from the Joint Photographic Experts Group (ISO/ITU-T). JPEG 2000 is very different from the original JPEG; whereas JPEG is DCT-based and examines images in a series of 8 x 8 pixel blocks, JPEG 2000 is wavelet-based using Discrete Wavelet Transform (DWT), to analyze the detail of pictures in a different way. Both coding and decoding require far more processing than JPEG, MPEG-2 or MPEG-4. Also JPEG 2000 is intra-frame only; there are no predictive frames (as in MPEG). Whereas MPEG tends to show macro blocks as it starts to fail, and the original JPEG shows ‘mosquito wings’ or ringing effects, JPEG 2000 can switch to lower data rates that can cause a softening of picture areas, which is far less noticeable. There are two file-name extensions; .JP2 is for ISO/IEC 15444-1 files and .JPX for ISO/IEC 15444-2 files.

JPEG 2000 is about twice as efficient as the equivalent I-only MPEG-2, and excels at high bit rates. It is used at up to 250Mb/s for DCI Digital Cinema applications, usually showing 24 pictures per second in 2K and 4K formats. It lends itself to a wide range of uses from portable digital cameras through to advanced pre-press and television acquisition – as well as Digital Cinema. Some favor it for use in TV distribution. The company intoPix, a specialist in JPEG 2000 technology, offers a video-over-IP solution using JPEG 2000 for HD and 4K UHD via 1Gb/s media networks with 10ms of latency. Its further technology developments are aimed at expanding the use of JPEG 2000 in TV.

See also: Compression, Compression ratio, DCT, Huffman coding, MPEG

Website: www.jpeg.org

JPEG (.JPG)

Joint Photographic Experts Group (ISO/ITU-T). It has defined many types of image compression. JPEG is a DCT-based data compression standard for individual pictures (intra-frame). It offers compression of between two and 100 times and has three levels of processing which are defined as: baseline, extended and lossless encoding.

JPEG baseline compression coding, which is overwhelmingly the most common in both the broadcast and computer environments, starts with applying DCT to 8 x 8 pixel blocks of the picture, transforming them into frequency and amplitude data. This itself may not reduce data but then the generally less visible high frequencies can be divided by a high ‘quantizing’ factor (reducing many to zero), and the more visible low frequencies by a much lower factor. The ‘quantizing’ factor can be set according to data size (for constant bit rate) or picture quality (constant quality) requirements – effectively adjusting the compression ratio. The final stage is Huffman coding which is lossless but can further reduce data by 2:1 or more.

Baseline JPEG coding creates .jpg files and it is very similar to the I-frames of MPEG, the main difference being they use slightly dissimilar Huffman tables.

See also: Motion JPEG

KLV

KLV is a data encoding protocol (SMPTE 336M). The Key is a unique, registered sequence of bits that defines the type of content that is coming (video, audio, EDL, etc) and Length – number of bytes ahead of Value, the content ‘payload’ itself. Compliance to KLV means that a wider range of equipment and applications can understand each others’ files.

See also: AAF, MXF

Latency (of data)

The delay between requesting and accessing data. For disk drives it refers to the delay due to disk rotation only, even though this is only one of several factors that determines time to access data from disks. The faster a disk spins the sooner it will be at the position where the required data is under the replay head. As disk diameters have decreased so rotational (spindle) speeds have tended to increase but there is still much variation. Modern 2.5-inch drives typically have spindle speeds of between 7,200 and 15,000 RPM, so one revolution is completed in 8 to 4 ms respectively. This is represented in the disk specification as average latency of 4 or 2 ms.

For solid-state ‘drives’ (SSD) the latency is much less resulting in faster access to data, particularly if the data is scattered around the store; here, SSD can be over 100 times faster than HDD, but just a few times faster for large unscattered data files.

MAM

Media Asset Management is used in modern broadcast and post production that increasingly depends on file-based operation rather than the use of tape. MAM can track and manage all aspects of the use and repurposing of media assets so it is clear which assets have been used where. This can help both in technical operations such as adjusting an edit, as well as commercial requirements such as billing.

Metadata

Data about data. In the media world it is data about the video and audio but it is not about the actual video or audio themselves. This is important for labeling and finding data – either in a ‘live’ data stream or an archive. Within studios and in transmission, digital technology allows information to be added. Some believe metadata will revolutionize every aspect of production and distribution. Metadata existed long before digital networks; video timecode and film frame numbers are but two examples. Today the metadata can also include the detail about the editing, color correction and effects work. Such history information allows a more open choice of equipment and the ability to retrace the detail of post production – should any changes be required.

See also: AAF, Content, Essence, History, MXF

Motion JPG

This is JPEG compression applied to digital video, where each frame or field (half frame) is individually compressed using JPEG encoding to reduce the amount of data. This is widely used in areas including video cameras, some webcams and in non-linear editing systems.

See also: JPEG, Field

MPEG-1

A compression scheme designed to work at 1.2 Mb/s, the basic data rate of CD-ROMs, so that video could be played from CDs. Its quality is not up to modern standards and it is not much used.

MPEG-2

ISO/IEC 13818. A family of inter- and intra-frame compression systems designed to cover a wide range of requirements from ‘VHS quality’ all the way to HDTV through a series of compression algorithm ‘profiles’ and image resolution ‘levels’. With data rates from below 4 to 100 Mb/s, this family includes the compression system that currently delivers digital TV to homes and that puts SD video onto DVDs as well as putting HD onto 6.35mm videotape for HDV.

In all cases MPEG-2 coding starts with analyzing 8×8-pixel DCT blocks and applying quantizing to achieve intra-frame compression that is very similar to JPEG. This compression is referred to as I-frame only MPEG-2. Producing much higher compression involves analyzing the frame-to-frame movement of 16×16-pixel ‘macroblocks’ to produce vectors that show the distance and direction of macroblock movement. Their correctness is a factor of coders’ quality and efficiency. This vector data is carried in the P (predictive) and B (bi-directional predictive) frames that exist between I frames (see diagram). SDTV transmissions and DVDs typically contain two I-frames per second typically using about 4 Mb/s or less – a big difference from the 180 Mb/s of uncompressed SD video. The set of images between I-frames is a Group of Pictures (GOP) – usually about 12 for 576/50I and 15 for 480/60I transmissions. These are called ‘long GOP’. The GOP length can vary during transmission – an I-frame may be forced at the start of a new sequence, such as after a video cut, or other occasions were there is a big change at the input.

MPEG-2 12 frame GOP

MPEG-2

*Note: for transmission the last ‘I’ frame is played out ahead of the last two ‘B’ frames to form the sequence I1, B1, B2, P1, B3, I1 B4, P2, B5, B6, P3, I2, B7, B8

Levels and profiles: MPEG-2 is a single compression standard that can operate on many different levels – picture source formats ranging from about VCR quality to full HDTV, and profiles – a collection of compression tools that make up a coding system. Current interest includes the Main Profile @ Main Level (MP@ML) covering current 525/60 and 625/50 broadcast television as well as DVD-video and Main Profile @ High Level (MP@HL) for HDTV. Besides the transmission/delivery applications which use 4:2:0 sampling, the 422 Profile (4:2:2 sampling) was designed for studio use and offers greater chrominance bandwidth which is useful for post production.

Blocking and ‘blockiness’: MPEG-2 artifacts generally show as momentary rectangular areas of picture with distinct boundaries. Their appearance generally depends on the amount of compression, the quality and nature of the original pictures as well as the quality of the coder. The visible blocks may be 8 x 8 DCT blocks or, most likely, ‘misplaced blocks’ – 16 x 16 pixel macroblocks, due to the failure of motion prediction/estimation in an MPEG coder or other motion vector system, e.g. a standards converter.

Audio: Digital audio compression uses auditory masking techniques. MPEG-1audio specifies mono or two-channel audio which may be Dolby Surround coded at bit rates between 32 kb/s to 384 kb/s. MPEG-2 audio specifies up to 7.1 channels (but 5.1 is more common), rates up to 1 Mb/s and supports variable bit-rate as well as constant bit-rate coding. MPEG-2 handles backward compatibility by encoding a two-channel MPEG-1 stream, then adds the 5.1/7.1 audio as an extension.

See also: Discrete 5.1 Audio, MP3

Websites:
www.mpeg.org
www.chiariglione.org/mpeg

MPEG-21

MPEG-21 (.m21 or .mp21) , standardized as ISO/IEC 21000, creates descriptions for a multimedia framework to provide a ‘big picture’ of how the system elements relate to each other and fit together. The resulting open framework for multimedia delivery and consumption includes content creators and content consumers as focal points to give creators and service providers equal opportunities in an MPEG-21 open market. This can also give the consumers access to a large variety of content in an practical manner. MPEG-21 defines a Digital Item as a basic unit of transaction. It is a structured digital object, including a standard representation, identification and metadata.

Website: www.chiariglione.org/mpeg

MPEG-4

ISO/IEC 14496. MPEG-4 covers three areas, digital television, interactive graphics applications (synthetic content) and interactive multimedia (Web distribution and access to content). It provides the standardized technological elements enabling the integration of the production, distribution and content access of the three fields.

Since its first publication in 1999, MPEG-4 video compression achieved quality targets with ever-lower bit rates. Like MPEG-2 the compression is DCT-based and uses inter- and intra-field compression but implements many refinements, such as a choice of block sizes and motion compensation accuracy of one-eighth of a pixel against MPEG-2’s half pixel.

MPEG-4 is guilty of generating too many names and versions. The highest quality MPEG compression technology is known by ISO and IEC as MPEG-4 AVC (Advanced Video Coding). It is also know by the ITU-T as H.264 or MPEG-4 part 10. Notable predecessors are MPEG-4 part 2 (ASP) and H.263. Significantly, MPEG-4 AVC achieves up to a 64 percent bit rate reduction over MPEG-2 for the same quality and it opened possibilities for HD DVDs and transmission, etc., as well as room to offer more SD DTV channels, or more quality. MPEG-4 also specifies low bit rates (5-64 kb/s) for mobile and Internet applications with frame rates up to 15 Hz, and images up to 352 x 288 pixels.

MPEG-4 AVC video coding and decoding are far more complex than MPEG-2 but Moore’s Law absorbed that technical challenge. QuickTime and RealPlayer were among early adopters of MPEG-4. While established systems need to stick to their MPEG-2, most if not all later video services use MPEG-4.

The interactive multimedia side of MPEG-4 includes storage, access and communication as well as viewer interaction and 3D broadcasting. Aural and visual objects (AVOs) represent the content which may be natural – from cameras or microphones, or synthetic – generated by computers. Their composition is described by the Binary Format for Scene description (BIFS) – scene construction information to form composite audiovisual scenes from the AVOs. Hence, a weather forecast could require relatively little data – a fixed background image with a number of cloud, sun, etc, symbols appearing and moving, audio objects to describe the action and a video ‘talking head’ all composed and choreographed as defined by the BIFS. Viewer interactivity is provided by the selection and movement of objects or the overall point of view – both visually and aurally.

Audio: This builds on previous MPEG standards and includes High Efficiency Advanced Audio Coding (HE-AAC). This nearly doubled the efficiency of MPEG-4 Audio, improving on the original AAC and offers better quality for the same bit rate as the ubiquitous MP3 codec (from MPEG-2). Stereo CD-quality at 48 kb/s and excellent quality at 32 kb/s is reported. This is not a replacement for AAC, but rather a superset which extends the reach of high-quality MPEG-4 audio to much lower bit rates. High Efficiency AAC decoders will decode both types of AAC for backward compatibility.

DVB has approved two MPEG-4 codecs for use for broadcast transport streams: H.264/AVC video codec (MPEG-4 Part 10) and the High Efficiency Advanced Audio Coding (HE-AAC) audio codec. This mandates support of Main Profile for H.264/AVC SDTV receivers, with an option for the use of High Profile. The support of High Profile is mandated for H.264/AVC HDTV receivers.

Websites:
www.chiariglione.org/mpeg
www.m4if.org

MPEG-7

The value of information often depends on how easily it can be found, retrieved, accessed, filtered and managed. MPEG-7, formally named ‘Multimedia Content Description Interface’, provides a rich set of standardized tools to describe multimedia content. Both human users and automatic systems that process audiovisual information are within its scope. It was intended to be the standard for description and search of large volumes of audio and visual content – including that from private databases, broadcast and via the Web. Applications include database retrieval from digital libraries and other libraries, areas like broadcast channel selection, multimedia editing and multimedia directory services.

MPEG-7 offers a set of audiovisual Description Tools (the metadata elements, their structure and relationships that are defined as Descriptors and Description Schemes). It specifies a Description Definition Language (DDL) so that material with associated MPEG-7 data can be indexed and allow fast and efficient searches. These searches will permit not only text-based inquiries, but also for scene, motion and visual content. Material may include stills, graphics, 3D models, audio, speech and video as well as information about how these elements are combined. Besides uses in program-making MPEG-7 could help viewers by enhancing EPGs and program selection.

Website: www.chiariglione.org/mpeg

MPEG

Moving Picture Experts Group. This is a working group of ISO/IEC for the development of international standards for compression, decompression, processing, and coded representation of moving pictures, audio and their combination. It has also extended into metadata. Four MPEG standards were originally planned but the accommodation of HDTV within MPEG-2 has meant that MPEG-3 is now redundant. MPEG-4 is very broad and extends into multimedia applications. MPEG-7 is about metadata and MPEG-21 describes a ‘big picture’ multimedia framework.

Websites:
www.chiariglione.org/mpeg
www.mpeg.org

MPEG-HEVC H.265

MPEG High Efficiency Video Coding was developed to achieve twice the efficiency of MPEG-4 AVC. Apart from having the potential to halve the bandwidth currently used to transmit HDTV services, it also halves the data needed to be transmitted for UHD. That means that a 4K UHD channel can fit into one DVB-T2 multiplex – the bandwidth that was used for one analog PAL TV channel.

Beyond helping to enable terrestrial, satellite and cable 4K transmissions, it is also a part of the Ultra HD Blu-ray specification.

 

See also: Display Resolution

MXF

The Material eXchange Format, SMPTE 377M, is aimed at the exchange of program material between file servers, video recorders, editing systems, tape streamers and digital archives, etc. It is a container, or wrapper, format that supports a variety of differently coded streams of essence (images and sound), together with metadata describing the material in the MXF file.

There are ten Operational Patterns defined by SMPTE standards. The main nine are the intersections along two-axes describing Item (segment) versus Package (complexity). This gives the combinations of 1) Single Item, 2) Playlist Items and 3) Edit Items against a) Single Package, b) Ganged Packages and c) Alternate Packages. By far the most common is OP-1a – Single Item, Single Package – which contains a single flat clip. The tenth operational pattern is OP-Atom which is used by Panasonic P2.

Bridging file and streaming transfers, MXF helps move material between AAF file-based post production and streaming program replay using standard networks. This set-up extends the reliable essence and metadata pathways of both formats to reach from content creation to playout. The MXF body carries the content. It can include compressed formats such as MPEG and DV as well as uncompressed video and can contain an interleaved sequence of picture frames, each with audio and data essence plus frame-based metadata. There are other scenarios where, for example, P2 MXF files contain a single essence track with no interleaving and no frame-based metadata. Also Panasonic AVC Long-G MXF files do interleave but not per-frame; instead they interleave partitions (chunks) of a constant duration, typically about 10 seconds. It is perfectly valid for MXF files to be metadata-only and this has no bearing on the operational pattern; for example, AS-02 bundles always contain a metadata-only version MXF file that references separate essence MXF files.

See also: AAF, AMWA

Website: www.pro-mpeg.org

NFS

Network File System. Developed by Sun Microsystems NFS allows sets of computers to access each other’s files as if they were locally stored. NFS has been implemented on many platforms and is considered an industry standard.

See also: IP

NTFS

New Technology File System – the standard file system of Windows NT and its descendants Windows 2000 through to Windows 8. It replaced Microsoft’s FAT file system used in MS-DOS and earlier Windows versions. Advantages include improved metadata support, advanced data structures, reliability, disk space use and extensions such as security access control lists (who can access), permitted operations and file system journaling that logs file changes. Full details are a Microsoft trade secret.

OMFI

Open Media Framework Interchange is an open standard developed by Avid, for post production interchange of digital media among applications and across platforms. It describes a file format and supports video, audio, graphics, animation and effects as well as comprehensive edit decision information. Transfers may be by removable media or over a high-speed network.

Website: www.avid.com

OpenEXR

OpenEXR is a file format developed by Industrial Light & Magic for high dynamic range (HDR) images that are used in computer imaging applications. It is used by ILM on motion pictures, has become ILM’s main image file format, and is released as free software. It offers a higher dynamic range than 8 or 10-bit pictures, support for 16-bit floating-point, 32-bit floating-point, and 32-bit integer pixels, up to 2:1 lossless compression algorithms, and extensibility to add new compression codecs and image types. It forms the container for the ACES color format.

See also: ACES, Color Transform Language

PAM

Production Asset Management could be considered as a subset of MAM It is intended to co-ordinate the work of all stages involved with post production, and so ensure it runs efficiently and meets planned deadlines and budgets. It can enhance collaboration and manage down to a detailed level for edit suites and media storage, and manage those contributing other elements, such as special effects. Management of items such as the original video, audio, EDLs, proxies, versioning, content protection, backup, can be included. But PAM is not tightly defined and some say that it ends when the media file is ‘flattened’, with all the effects, corrections, cuts, mixes, etc, are applied and resolved to produce one layer of video and the finished tracks of audio.

ProRes

A range of lossy, video compression systems developed by Apple Inc. Designed for editing it is described as ‘intermediate’, between uncompressed and more highly compress delivery quality. ProRes 422 can work with formats from SD to 5K using 10-bit, I-frame only, variable bit rate coding. For HD 60i there are three qualities; Normal 147 Mb/s, High-Quality 220 Mb/s and ProRes (LT) 100Mbit/s. There is also ProRes Proxy at 36 Mb/s for offline. For SD there are Normal 42 Mb/s and High-Quality 63 Mbit/s.

ProRes 4444 adds support for a 16-bit alpha (key) channel, and video sampling up to 12-bit.

See also: Quick Time

QuickTime

QuickTime is a multimedia framework developed by Apple Inc. capable of handling various formats of digital video, media clips, sound, text, animation, music, and several types of interactive panoramic images. Running on either OSX or Windows operating systems, QuickTime supports software packages including iTunes, QuickTime Player and Safari.

See also: ProRes

 

Raw data (a.k.a. source data)

Data that has not been processed for use. It is often written as ‘RAW’, which may make you think it is an acronym. It is not.

Raw data usually applies to the output of digital cinematography cameras that can generally deliver images that include the full brightness range that its imager can extract from a scene. The data has not been tampered with, not processed for color or to suit any target viewing conditions, such as cinema or gamma corrected for home TV viewing. The raw data is as the imager saw it with debayering applied where needed.

SAN

Storage Area Network is a well-established method of providing shared video storage and can offer platform-independent storage that may be accessed from, say, Windows, Linux and Mac OS workstations. It allows applications direct access to shared storage by cutting out the usual client-server ‘middle men’ to provide improved workflow and better work sharing on a common store.

SAN

The design recognizes that moving large amounts of data (video) is inconsistent with normal-network general-data traffic. Therefore it forms a separate network to connect data-hungry workstations to a large, fast array of disks. Although any network technology could be used, Fibre Channel predominates with current speeds of up to 14 Gb/s. SANs are scalable but additions may be complex to implement. Currently, expansion is ultimately limited by architecture and management considerations. However, in practice it can be difficult to sustain multiple high bandwidth (e.g. for HD or 4K) streams from a SAN. Quantel’s Genetic Engineering is designed to solve this problem and is capable of playing back multiple 2K and 4K streams simultaneously.

See also: FAN, Fibre Channel, NAS

Website: www.snia.org

Schema

A collection of tables and constraints that describe the structure of a database. It provides a level of security as no one else can interpret the stored database without the schema; it is just a collection of figures. The schema organizes the database to allow scalability for expansion and defines efficient operation to suit a particular application.

SNMP

Simple Network Management Protocol is the Internet standard protocol developed to manage nodes (servers, workstations, routers, switches, hubs, etc.) on IP networks. It enables network administrators to manage network performance, find and solve network problems, and plan for network growth. SNMP works by sending Protocol Data Units (PDUs) messages to different parts of a network. Agents, SNMP-compliant devices, store data about themselves in Management Information Bases (MIBs) and return this data to the SNMP requesters.

Variable bit rate (VBR) compression

While many video compression schemes are ‘constant bit rate’ – designed to produce fixed data rates irrespective of the complexity of the video, VBR offers the possibility of fixing a constant picture quality by varying the bit-rate of, typically, MPEG-2 or MPEG-4 compressed video according to the needs of the pictures. This allows the images that require little data, like still or slow moving video sequences, to use less data and to use more for those that need it where there is more detail or/and movement; so maintaining a constant quality. This reduces the need for storage on DVDs, while delivering better overall quality, or more efficient allocation of total available bit-rate in a multi-channel broadcast multiplex.

See also: Constant bit rate, DVD, Statistical multiplexing

VC-1

VC-1 is a video codec specification (SMPTE 421M-2006) implemented by Microsoft as Windows Media Video (WMV) 9, and specified in Blu-ray Disc, and many others. It is designed to achieve state-of-the-art compressed video quality at bit rates ranging from very low to very high with low computational complexity for it to run well on PC platforms. The codec can handle 1920 x 1080 at 6 to 30 Mb/s for high-definition video and is capable of higher resolutions such as 2K for digital cinema, and of a maximum bit rate of 135 Mb/s. An example of very low bit rate video would be 160 x 120 pixel at 10 kb/s.

VC-1 uses some similar transforms to H.261 (1990, the first practical digital coding standard) but much more like H.264/AVC. It includes some distinctive innovations and optimizations. These include 16-bit transforms to help to minimize decoder complexity and interlace coding using data from both fields to predict motion compensation. Also fading compensation improves compression efficiency for fades to/from black and a modified de-blocking filter helps handling areas of high detail.

Individual opinions differ but broadly speaking VC-1 offers at least similar performance and efficiency to H.264/AVC; some say it looks better. VC-1 offers a number of profiles for coding features, and levels of quality combinations defining maximum bit rates. These have a wide range from 176 x 144/15P which may be used for mobile phones, to 2K (2048 x 1536/24P) for movie production.

ProfileLevelMax Bit RateResolutions and Frame Rate  
SimpleLow96Kb/s176 x 144 @ 15 Hz (QCIF)
Medium384 Kb/s240 x 176 @ 30 Hz
352 x 288 @ 15 Hz (CIF)
MainLow2 Mb/s320 x 240 @24 Hz (QVGA)
Medium10 Mb/s720 x 480 @ 30 Hz (480p)
720 x 576 @ 25 Hz (576p)
High20 Mb/s1920 x 1080 @30 Hz (1080p)
AdvancedL02 Mb/s352 x 288 @ 30 Hz (CIF)
L110 Mb/s720 x 480 @ 30 Hz (NTSC-SD)
720 x 576 @ 25 Hz (PAL-SD)
L220 Mb/s720 x 480 @60 Hz (480p)
1280 x 720 @ 30 Hz (720p)
L345 Mb/s1920 x 1080 @24 Hz (1080p)
1920 x 1080 @30 Hz (1080i)
1280 x 720 @60 Hz (720p)
L4135 Mbps1920 x 1080 @60 Hz (1080p)
2048 x 1536 @ 24 Hz

See also: MPEG-4

Websites:
www.microsoft.com
www.smpte.org

VC-2

Standardized by SMPTE, VC-2 (also known as Dirac Pro) is a video codec technology developed by the BBC. VC-2 is open source and royalty-free for all to use. It is an intra-frame compression scheme aimed at professional production and post production. Compression ratios are in the range 2:1 to 16:1, and typical VC-2 applications are seen to include desktop production over IP networks, reducing disk storage bandwidth in D-Cinema production and moving HD video over legacy infra-structure. A current application provides near lossless compression to enable the use of HD-SDI to carry 1080/50P and 1080/60P, which would otherwise require new 3G SDI infrastructure.

Website: www.bbc.co.uk/rd/publications/whitepaper238

XAVC

A video compression system developed by Sony and released in 2012. Designed for professional use in acquisition and post production, XAVC uses the highest level (5.2) of H.264/MPEG-4 AVC and offers some things that plain vanilla H.264 XAVC does not, such as encoding 1080/50P and 1080/60P. At the high performance end it supports 4K at both 4096 x 2160 (cinema) and 3840 x 2160 (video) resolutions at up to 60 f/s. With available bit depths of 8, 10 and 12, 4:2:0, 4:2:2 and 4:4:4 sampling and bit rates ranging from 15 to 960 Mb/s, XAVC can be used for a wide range of applications.

As H.264 is an advanced compression system, XAVC can offer high quality performance at relatively low bit rates (and smaller / longer storage) with a choice of either intra-frame or long-GOP codecs. The compressed video can be wrapped in an MXF OP1a container which is widely used in broadcast.

XAVC-S is the 8-bit consumer version of XAVC. It offers lower bits rates than XAVC and is wrapped in an MPEG-4 container. It is designed for the shorter, less complex workflows typical of consumer production.

XDCAM

Launched in 2003, Sony’s XDCAM professional camcorder products have evolved with technology. The first model was for SD television and made use of its Professional Disc (PD), an application of Blu-ray Disc, as the on-board recording medium. The product range included camcorders, mobile and studio decks which are designed to take advantage of the size, weight, data speed and re-record features of the PD technology. It used the DVCAM codec and record SD 4:1:1 (480-line) and 4:2:0 (576-line) video at 25 Mb/s onto the PD.

XDCAM HD camcorder images were native 1440 x 1080 and recorded as HDV: 1080/59.94I, 50I, 29.97P, 25P, and native 23.98P video using MPEG-2 MP@HL with compression and 4:2:0 sampling. Users could select 35 (HQ), 25 (SP), or 18 (LP) Mb/s bit rates according to picture quality and recording length requirements, ranging from 60 to 120 minutes. There were four channels of 16-bit, 48 kHz audio.

XDCAM EX takes the same ideas but records to solid-state storage in place of Blu-ray disc.

XDCAM HD422 is a family that includes a selection of cameras, recorders again including solid-state, and accessories.

See also: Professional Disc