Multimedia Unit - 3

UNIT-III

Basics of Video- Anlog and Digital Video, How to use video on PC, introduction to graphics accelerator cards, directX, introduction to ad/dv and IEE1394 cards, digitization of analog video to digital video, interlacing and non interlacing, brief note on various video standards-NTSC, PAL, SECAM, HDTV. Introduction to video capturing media and instrument, videodisk, DVCAM, camcorder. Introduction to digital video compression techniques and various file formats= avi, mpeg, mov, real video.

Brief introduction to video editing and movie making tools- quick time, video for windows and adobe premier.

Analog Video

When light reflected from an object passes through a video camera lens that light is converted into electronic signals by a special sensor called charged couple device (CCD). Top-quality broadcast cameras may have as many as three CCDs (one for each color of red, green, and blue) to enhance the resolution of the camera. The output of the CCD is processed by the camera into a signal containing three channels of color information and synchronization pulses (sync): There are several video standards for managing CCD output, each dealing with the amount of separation between the components of the signal. The more separation of the color information in the signal results in higher quality of the image (and the more expensive the equipment).

If each channel of color information is transmitted as a separate signal on its own conductor, the signal output is called RGB (red, green, and blue), which is the preferred method for higher quality and professional video work. Output can also be split into two separate color channels which results in poor quality of video.

Digital Video

Analog video has been used for years in recording / editing studios and television broadcasting. For the purpose of incorporating video content in multimedia production video needs to be converted into the digital format.

It has already been mentioned that processing digital video on personal computers was very difficult initially, firstly because of the huge file sizes required, and secondly of the large bit rate and processing power required. Full screen video only became a reality after advent of the Pentium-II processor together with fast disks capable of delivering the required output. Even with these powerful resources delivering video files was difficult until the reduction in prices of compression hardware and software. Compression helped to reduce the size of video files to a great extent which required a lower bit-rate to transfer them over communication buses. Nowadays video is rarely viewed in; the uncompressed form unless there is specific reason for doing so, e.g. to maintain the high quality, as for medical analysis.

Digitizing video in general requires a, video capture card and associated recording software. The capture card is usually installed at the PC end which accepts analog video from a source device and converts it into a digital file using recording software. Alternatively the capture card can be inside a digital video camera which is capable of producing a digital video output and recording it onto a tape. The digital output from a digital video camera can also be fed to a PC after necessary format conversion.

Basics of Video

Of all the multimedia elements, video places the highest performance demand on your computer and its memory and storage. Consider that a high-quality color still image on a computer screen could require as much as a megabyte of storage memory. Multiply this by 30-the number of times per second that still picture is replaced to provide the appearance of motion-and you would need 30 megabytes of storage to play your video for one second, or 1.8 gigabytes of storage for a minute. Just moving these entire pictures from computer memory to the screen at that rate would challenge the processing capability of a super- computer. Multimedia technologies and re-search efforts today deal with compressing digital video image data into manageable streams of information so that a massive amount of image can be squeezed into a comparatively small data file that still delivers a good viewing experience on the intended viewing platform during playback.

Carefully planned, well-executed video clips can make a dramatic difference in a multimedia project.

Using Video On PC

Analog video needs to be converted to the digital format before it can be displayed on a PC screen. The procedure for conversion involves two types of devices- source devices and capture devices.

The source and source device can be one of the following:

camcorder with pre-recorded video tape

VCP with pre-recorded video tape

Video camera with live footage.

We need Video capture card to convert analog signal to digital signal along with video capture Software such as AVI capture, AVI to MPEG Converter, MPEG capture, DAT to MPEG Converter or MPEG Editor.

DirectX

Microsoft changed the entire multimedia standards game with its DirectX standard in Windows 95.

The idea was that DirectX offered a load of commands, also known as APIs, which did things like "make a sound on the left" or "draw a sphere in front". Games would then simply make DirectX calls and the hardware manufacturers would have to ensure their sound and graphics card drivers understood them.

The audio portion of DirectX 1 and 2 was called DirectSound, and this offered basic stereo left and right panning effects. As with other DirectX components, this enabled software developers to write directly to any DirectX-compatible sound card with multiple audio streams, while utilizing 3D audio effects. Each audio channel can be treated individually, supporting multiple sampling rates and the ability to add software-based effects. DirectSound itself acts as a sound-mixing engine, using system RAM to hold the different audio streams in play for the few milliseconds they must wait before being mixed and sent on to the sound card. Under ideal conditions, DirectSound can mix and output the requested sounds in as little as 20 milliseconds.

DirectX 3 introduced DirectSound3D (DS3D) which offered a range of commands to place a sound anywhere in 3D space. This was known as positional audio, and required significant processing power. Sadly we had to wait for DirectX 5 before Microsoft allowed DS3D to be accelerated by third-party hardware, reducing the stress on the main system CPU. DirectX 6 supported DirectMusic, offering increased versatility in composing music for games and other applications.

DS3D positional audio is one of the features supported by the latest generation of PCI sound cards. Simply put, positional audio manipulates the characteristics of sounds to make them seem to come from a specific direction, such as from behind or from far to the left. DirectSound3D gives game developers a set of API commands they can use to position audio elements. Furthermore, as with much of DirectX, DirectSound3D is scaleable: if an application asks for positional effects and no hardware support for such effects is found, then DirectSound3D will provide the necessary software to offer the positional effect, using the CPU for processing.

DS3D may have supported positional audio, but it didn't offer much support for adding reverb, let alone considering individual reflections, to simulate different environments. Fortunately DS3D does support extensions to the API, and this need was soon met by a couple of new sound standards which have gained widespread support from games developers: Aureal's A3D technology and Creative Technology's Environmental Audio Extensions (EAX).

 

Broadcast video standards

Three analog broadcast video standards are commonly in use around the world: NTSC, PAL, and SECAM. In the United States, the NTSC standard is being phased out, replaced by ATSC digital television standard. Because these standards and formats are not easily interchangeable, it is important to know where your multimedia project will be used. A video cassette recorded in USA which uses NTSC will not play on a television set in any European country (which uses either PAL or SECAM), even thought the recording method and style of the cassette is “VHS”.  Likewise, tapes recorded in European PAL or SECAM formats will not play back on an NTSC video cassette recorder. Each system is based on a different standard that defines the way information is encoded to produce the electronics signal that ultimately creates a television picture. Multi-format VCRs can play back all three standards but typically cannot dub from one standard to another; dubbing between standards still require high-end specialized equipment.

National Television Standard Committee (NTSC)

The United States, Canada, Mexico, Japan, and many other countries use a system for broadcasting and displaying video that is based upon the specifications set forth by the 1952 National Television Standards Committee. These standards define a method for encoding information into the electronic signal that ultimately creates a television picture. As specified by the NTSC standard, a single frame of video is made up of 525 horizontal scan lines drawn onto the inside face of a phosphor-coated picture tube every 30th of a second by a fast-moving electron beam. The drawing occurs so fast that your eye perceives the image as stable. The electron beam actually makes two passes as it draws a single video frame, first laying down all the odd-numbered lines, then all the even-numbered lines. Each of these passes (which happen at a rate of 60 per second, or 60 Hz) paints a field, and the two fields are combined to create a single frame at a rate of 30 frames per second (fps). (Technically, the speed is actually 29.97 Hz.) This process of building a single frame from two fields is called interlacing, a technique that helps to prevent flicker on television screens. Computer monitors use a different progressive-scan technology, and draw the lines of an entire frame in a single pass, without interlacing them and without flicker.

Phase Alternate Line (PAL)

The Phase Alternate Line (PAL) system is used in the United Kingdom, Western Europe, Australia, South Africa, China, and South America. PAL increases the screen resolution to 625 horizontal lines, but slows the scan rate to 25 frames per second. As with NTSC, the even and odd lines are interlaced, each field taking 1/50th of a second to draw (50 Hz).

Sequential Color and Memory (SECAM)

The Sequential Color and Memory is used in France, Eastern Europe, the former USSR, and a few other countries. Although SECAM is a 625-line, 50 Hz system, it differs greatly from both the NTSC and the PAL color systems in its basic technology and broadcast method. Often, however, TV sets sold in Europe utilize dual components and can handle both PAL and SECAM systems.

Advanced Television Standard Committee (ATSC) and Digital Television (DTV)

What started as the High Definition Television (HDTV) initiative of the Federal Communications Commission in the 1980s, changed first to the Advanced Television (ATV) initiative and then finished as the Digital Television (DTV) initiative by the time the FCC announced the change in 1996. This standard, slightly modified from the Digital Television Standard and Digital Audio Compression Standard, moves U.S. television from an analog to digital standard and provides TV stations with sufficient bandwidth to present four or five Standard Television signals (STV, providing the NTSC's resolution of 525 lines with a 3:4 aspect ratio, but in a digital signal) or one HDTV signal (providing 1,080 lines of resolution with a movie screen's 16:9 aspect ratio). More significantly for multimedia producers, this emerging standard allows for transmission of data to computers and for new ATV interactive services. As of May 2003, 1,587 TV stations in the United States (94 percent) had been granted a DTV construction permit or license. Among those, 1,081 stations were actually broadcasting a DTV signal, almost all simultaneously-casting their regular TV signal. According to the current schedule, all the stations are to cease broadcasting on their analog channel and completely switch to a digital signal by 2006.

High Definition Television (HDTV)

It provides high resolution in 16: 9 aspect ratios. This aspect ratio allows the viewing of Cinemascope and Panavision movies. There is contention between the broadcast and computer industries about whether to use interlacing or progressive-scan technologies. The broadcast industry has promulgate an ultra-high-resolution, 1920xl080 interlaced format to become the cornerstone of a new generation of high-end entertainment centers, but the computer industry would like to settle on a 1280x720 progressive-scan system for HDTV. While the 1920xl080 format provides more pixel than the 1280x720 standard, the refresh rates are quite different. This higher-resolution interlaced format delivers only half the picture every 1/60 of a second, and because of the interlacing, on highly detailed images there is a great deal of screen flicker at 30 Hz. The computer people argue that the picture quality at 1280x720 is superior and steady. Both formats have been included in the HDTV standard by the Advanced Television System!

Today's multimedia monitors typically use a screen pixel ratio of 4:3 (800x600), but the new HDTV standard specifies a ratio of 16:9 (1280x720), much wider than tall. There is no easy way to stretch and shrink existing graphics material to this new aspect ratio, so new multimedia design and interface principles will need to be developed for HDTV presentations.

Digitization of Analog Video to Digital Video

Video, like sound, is usually recorded and played as an analog signal. It must therefore be digitized in order to be incorporated into a multimedia title. A video source, such as a video camera, VCR, TV, or videodisc, is connected to a video capture card in a computer. As the video source is played, the analog signal is sent to the video card and converted into a digital file that is stored on the hard drive. At the same time, the sound from the video source is also digitized.

One of the advantages of digitized video is that it can be easily edited. Analog video, such as a videotape is linear; there is a beginning, middle, and end. If you want to edit it, you need to continually rewind, pause, and fast-forward the tape to display the desired frames. Digitized video, on the other hand, allows random access to any part of the Video, and editing can be as easy as the cut-and-paste process in a word processing program. In addition, adding special effects such as fly-in titles and transitions is relatively simple.

Introduction to Video Compression Technique

Because of the large sizes associated with video files, video compression, decompression programs, known as codecs, have been developed. These programs can substantially reduce the size of video files, which means that more video can fit on a single CD and that the speed of transferring video from a CD to the computer can be increased. There are two types of compression: loss less and lossy. Lossy compression actually eliminates some of the data in the image and therefore provides greater compression ratios than lossless compression. When the compression ratio is made high the quality of decompressed image becomes poor. Thus, the trade-off is file size versus image quality. Lossy compression is applied to video because some drop in the quality is not noticeable in moving images.

Certain standards have been established for compression programs, including JPEG (Joint Photographic Experts Groups) and MPEG (Motion Picture Experts Group). Both of these programs reduce the file size of graphic images by eliminating redundant information. Often areas of an image (especially backgrounds) contain similar information. JPEG compression identifies these areas and stores them as blocks of pixels instead of pixel by pixel, thus reducing the amount of, information needed to store the image. Compression rations of 20: 1 can be achieved without substantially affecting image quality. A 20: 1 compression ratio would reduce a 1 MB file to only 50 KB.

MPEG adds another process to the still-image compression when working with video. MPEG looks for the changes in the image from frame to frame. Key frames are identified every few frames, and the changes that occur from key frame to key frame are recorded.

MPEG can provide greater compression ratios than JPEG, but it requires hardware (a card inserted in the computer) that is not needed for JPEG compression. This limits the use of MPEG compression for multimedia titles, because MPEG cards are not standard on the typical multimedia playback system.

Two widely used video compression software programs are Apple's QuickTime (and Quicklime for Windows) and Microsoft's Video for Windows. Quicklime is popular because it runs on both, Apple and Windows-based computers. It uses lossy compression coding and can achieve ratios of 5: 1 to 25: 1. Video for Windows uses a format called Audio Video Interleave (AVI) which, like QuickTime, synchronizes the sound and, motion of a video file. In this example, the unchanging background is stored only once every 15 frames; only the moving spaceship is recorded frame by frame.

Video Formats

The AVI Format

The AVI (Audio Video Interleave) format was developed by Microsoft.The AVI format is supported by all computers running Windows, and by all the most popular web browsers. It is a very common format on the Internet, but not always possible to play on non-Windows computers. Videos stored in the AVI format have the extension .avi.

The Windows Media Format

The Windows Media format is developed by Microsoft. Windows Media is a common format on the Internet, but Windows Media movies cannot be played on non-Windows computer without an extra (free) component installed. Some later Windows Media movies cannot play at all on non-Windows computers because no player is available. Videos stored in the Windows Media format have the extension .wmv.

The MPEG Format

The MPEG (Moving Pictures Expert Group) format is the most popular format on the Internet. It is cross-platform, and  supported by all the most popular web browsers. Videos stored in the MPEG format have the extension .mpg or .mpeg.

The QuickTime Format

The QuickTime format is developed by Apple. QuickTime is a common format on the Internet, but QuickTime movies cannot be played on a Windows computer without an extra (free) component installed. Videos stored in the QuickTime format have the extension .mov.

The RealVideo Format

The RealVideo format was developed for the Internet by Real Media. The format allows streaming of video (on-line video, Internet TV) with low bandwidths. Because of the low bandwidth priority, quality is often reduced.

Videos stored in the RealVideo format have the extension .rm or .ram.

The Shockwave (Flash) Format

The Shockwave format was developed by Macromedia. The Shockwave format requires an extra component to play. This component comes preinstalled with the latest versions of Netscape and Internet Explorer.

Videos stored in the Shockwave format have the extension .swf.

Software for Capturing and Editing Videos

Several steps are needed to prepare video to be incorporated into a multi- media title. These include capturing and digitizing the video from some video source, such as a video camera, VCR, TV, or videodisc; editing the digitized video; and compressing the video. Some software programs specialize in one or the other of these steps, and other programs, such as Adobe Premiere can perform all of them. Although capturing and compressing are necessary, it is editing that receives the most attention. Editing digitize video is similar to editing analog video, except that it is easier. For one this it is much quicker to access frames in digital form than in analog. For example, with analog video, a lot of time is spent fast-forwarding a rewinding the videotape to locate the desired frames; whereas with digital editing you can quickly jump from the first frame to the last-or anywhere in between. Removing frames or moving them to another location is as easy as the cut-and-paste process in a word processing program. The following are some other features that may be included in editing software programs:

Incorporating transitions such as dissolves, wipes, and spins

Superimposing titles and animating them, such as a fly-in logo

Applying special effects to various images, such as twisting, zooming, rotating, and distorting

Synchronizing sound with the video

Applying filters that control color balance, brightness and contrast, blurring, distortions, and morphing

Introduction to Video Capture Media and Instruments:

Digital video cameras come in two different image capture formats: interlaced and progressive scan. Interlaced cameras record the image in alternating sets of lines: the odd-numbered lines are scanned, and then the even-numbered lines are scanned, then the odd-numbered lines are scanned again, and so on. One set of odd or even lines is referred to as a "field", and a consecutive pairing of two fields of opposite parity is called a frame.

A progressive scanning digital video camera records each frame as distinct, with both fields being identical. Thus, interlaced video captures twice as many fields per second as progressive video does when both operate at the same number of frames per second.

Progressive scan camcorders are generally more desirable because of the similarities they share with film. They both record frames progressively, which results in a crisper image. They can both shoot at 24 frames per second, which results in motion strobing (blurring of the subject when fast movement occurs). Thus, progressive scanning video cameras tend to be more expensive than their interlaced counterparts

Standard film stocks such as 16 mm and 35 mm record at 24 frames per second. For video, there are two frame rate standards: NTSC, and PAL, which shoot at 30/1.001 (about 29.97) frames per second and 25 frames per second, respectively.

Digital video can be copied with no degradation in quality. No matter how many generations a digital source is copied, it will be as clear as the original first generation of digital footage.

Digital video can be processed and edited on an NLE, or non-linear editing station, a device built exclusively to edit video and audio. These frequently can import from analog as well as digital sources, but are not intended to do anything other than edit videos. Digital video can also be edited on a personal computer which has the proper hardware and software. Using an NLE station, digital video can be manipulated to follow an order, or sequence, of video clips.

Digital video is used outside of movie making. Digital television (including higher quality HDTV) started to spread in most developed countries in early 2000s. Digital video is also used in modern mobile phones and video conferencing systems. Digital video is also used for Internet distribution of media, including streaming video.

Many types of video compression exist for serving digital video over the internet, and onto DVDs. Although digital technique allows for a wide variety of edit effects, most common is the hard cut and an editable video format like DV-video allows repeated cutting without loss of quality, because any compression across frames is lossless. While DV video is not compressed beyond its own codec while editing, the file sizes that result are not practical for delivery onto optical discs or over the internet, with codecs such as the Windows Media format, MPEG2, MPEG4, Real Media, the more recent H.264, and the Sorenson media codec. Probably the most widely used formats for delivering video over the internet are MPEG4 and Windows Media, while MPEG2 is used almost exclusively for DVDs, providing an exceptional image in minimal size but resulting in a high level of CPU consumption to decompress.

In analog systems, the video signal from the camera is delivered to the Video In connector(s) of a VCR, where it is recorded on magnetic video tape. A camcorder combines both camera and tape recorder in a single device. One or two channels of sound may also be recorded on the video tape (mono or stereo). The video signal is written to tape by a spinning recording head that changes the local magnetic properties of the tape's surface in a series of long diagonal stripes. Because the head is tilted at a slight angle compared with the path of the tape, it follows a helical (spiral) path, which is called helical scan recording. Each stripe represents information for one field of a video frame. A single video frame is made up of two fields that are interlaced. Audio is recorded 0n a separate straight- line track at the top of the videotape, although with some recording systems, sound is recorded helically between the video tracks. At the bottom of the tape is a control track containing the pulses used to regulate speed. Tracking is fine adjustment of the tape so that the tracks are properly aligned as the tape moves across the playback head. This is how your VCR works.

In digital systems, the video signal from the camera is first digitized as a single frame, and the data is compressed before it is written to the tape in one of several proprietary and competing formats: DV, DVCPRO, or DVCAM.

Video-capture capability is not confined to camcorders. Cellphones, digital single lens reflex and compact digicams, laptops, and personal media players frequently offer some form of video-capture capability. In general, these multipurpose-devices offer less functionality for video-capture, than a traditional camcorder. The absence of manual adjustments, external-audio input, and even basic usability functions (such as autofocus and lens-zoom) are common limitations. More importantly, few can capture to standard TV-video formats (480p60, 720p60, 1080i30), and instead record in either non-TV resolutions (320x240, 640x480, etc.) or slower frame-rates (15fps, 30fps.)

Different type of storage media for Video

Some recent camcorders record video on flash memory devices, Microdrives, small hard disks, and size-reduced DVD-RAM or DVD-Rs using MPEG-1, MPEG-2 or MPEG-4 formats. Most other digital consumer camcorders record in DV or HDV format on tape and transfer content over FireWire.

Camcorders are often classified by their storage device: VHS, VHS-C, Betamax, Video8 are examples of older, videotape-based camcorders which record video in analog form. Newer camcorders include Digital8, MiniDV, DVD, Hard Disk and solid-state (flash) semiconductor memory, which all record video in digital form. (Please see the digital video page for details.) In older digital camcorders, the imager-chip, the CCD was considered an analog component, so the digital namesake is in reference to the camcorder's processing and recording of the video. Many next generation camcorders use a CMOS imager, which register photons as binary data as soon as the photons hit the imager

The IEEE 1394 interface

It is a serial bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used by personal computers, as well as in digital audio, digital video, automotive, and aeronautics applications. The interface is also known by the brand names of FireWire (Apple), i.LINK (Sony), and Lynx (Texas Instruments). IEEE 1394 replaced parallel SCSI in many applications, because of lower implementation costs and a simplified, more adaptable cabling system.

IEEE 1394 was adopted as the High-Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control.FireWire is also available in wireless, fiber optic, and coaxial versions using the isochronous protocols.

Nearly all digital camcorders have included a four-circuit 1394 interface, though, except for premium models, such inclusion is becoming less common. It remains the primary transfer mechanism for high end professional audio and video equipment. Since 2003 many computers intended for home or professional audio/video use have built-in FireWire/i.LINK ports, especially prevalent with Sony and Apple's computers. The legacy (alpha) 1394 port is also available on premium retail motherboards.

A Camcorder

A camcorder (video CAMera reCORDER) is an electronic device that combines a video camera and a video recorder into one unit. Equipment manufacturers do not seem to have strict guidelines for the term usage. Marketing materials may present a video recording device as a camcorder, but the delivery package would identify content as video camera recorder.

In order to differentiate a camcorder from other devices that are capable of recording video, like cell phones and compact digital cameras, a camcorder is generally identified as a portable device having video capture and recording as its primary function.

The earliest camcorders employed analog recording onto videotape. Since the 1990s digital recording has become the norm, but tape remained the primary recording media. Starting from early 2000s tape as storage media is being gradually replaced with tapeless solutions like optical disks, hard disk drives and flash memory.

All tape-based camcorders use removable media in form of video cassettes. Camcorders that do not use magnetic tape are often called tapeless camcorders and may use optical discs (removable), solid-state flash memory (removable or built-in) or a hard disk drive (removable or built-in).

Camcorders that permit using more than one type of media, like built-in hard disk drive and memory card, are often called hybrid camcorders

Video cameras originally designed for television broadcast were large and heavy, mounted on special pedestals, and wired to remote recorders located in separate rooms.

As technology advanced, out-of-studio video recording was made possible by means of compact video cameras and portable video recorders. The recording unit could be detached from the camera and carried to a shooting location. While the camera itself could be quite compact, the fact that a separate recorder had to be carried along made on-location shooting a two-man job.  Specialized video cassette recorders were introduced by both JVC (VHS) and Sony (Umatic & Betamax) to be used for mobile work.

In 1982 Sony released the Betacam system. A part of this system was a single camera-recorder unit, which eliminated the cable between camera and recorder and dramatically improved the freedom of a cameraman. Betacam quickly became the standard for both news-gathering and in-studio video editing.

In 1983 Sony released the first consumer camcorder - the Betamovie BMC-100P. It used a Betamax cassette and could not be held with one hand, so it was typically resting on a shoulder. In the same year JVC released the first camcorder based on VHS-C format. In 1985 Sony came up with its own compact video cassette format — Video8. Both formats had their benefits and drawbacks, and neither won the format war.

In 1985, Panasonic, RCA, and Hitachi began producing camcorders that recorded to full-sized VHS cassette and offered up to 3 hours of record time. These shoulders mount camcorders found use for industrial videographers, and college TV studios. Super VHS full-sized camcorders were released in 1987 which exceeded broadcast quality and provided an inexpensive way to collect news segments or videographies.

In 1986 Sony introduced the first digital video format, D1. Video was recorded in uncompressed form and required enormous bandwidth for its time. In 1992 Ampex used D1 form-factor to create DCT, the first digital video format that utilized data compression. The compression utilized discrete cosine transform algorithm, which is used in most modern commercial digital video formats.

In 1995 Sony, JVC, Panasonic and other video camera manufacturers launched DV. Its variant using a smaller MiniDV cassette quickly became a de-facto standard for home and semi-professional video production, for independent filmmaking and for citizen journalism.

In 2000 Panasonic launched DVCPRO HD, expanding DV codec to support high definition. The format was intended for use in professional camcorders and used full-size DVCPRO cassettes. In 2003 Sony, JVC, Canon and Sharp introduced HDV, the first truly affordable high definition video format, which used inexpensive MiniDV cassettes.

In 2003 Sony pioneered XDCAM, the first tapeless video format, which uses Professional Disc as recording media. Panasonic followed next year, offering P2 solid state memory cards as recording medium for DVCPRO HD video.

In 2006 Panasonic and Sony introduced AVCHD as an inexpensive consumer-grade tapeless high definition video format. Presently AVCHD camcorders are manufactured by Sony, Panasonic, Canon, JVC and Hitachi.

In 2007 Sony introduced XDCAM EX, which offers similar recording modes to XDCAM HD, but records on SxS memory cards.

With proliferation of file-based digital formats the relationship between recording media and recording format became weaker than ever: the same video can be recorded onto different media. With tapeless formats, recording media has become a storage device for digital files, signifying convergence of video and computer industries.

DVCAM

Sony's DVCAM is a professional variant of the DV standard that uses the same cassettes as DV and MiniDV, but transports the tape 50% faster having 50% wider track, 15 micrometres instead of 10 micrometres. This variant uses the same codec as regular DV, however, the wider track lowers the chances of dropout errors. The LP mode of consumer DV is not supported. All DVCAM recorders and cameras can play back DV material, but DVCPRO support was only recently added to some models like DSR-1800, DSR-2000, DSR-1600. DVCAM tapes (or DV tapes recorded in DVCAM mode) have their recording time reduced by one third.

Because of the wider track, DVCAM has the ability to do a frame accurate insert tape edit. DV will vary by a few frames on each edit compared to the preview. Another feature of DVCAM is locked audio. If several generations of copies are made on DV, the audio sync may drift. On DVCam this does not happe

Video Capture Card

Video Capture Card  is essentially an expansion board that can handle a variety of different audio and video input signals and convert them into analog to digital or vice versa. Rendering support for a variety of TV signal formats, e.g. NTSC, PAL, SECAM, imposes a level of complexity in the design together with recently introduced standards for HDTV. A typical circuit board consists of the following components: 

Video INPUT port to accept the video input signals from NTSC/PAL/SECAM broadcast signals, video camera or VCR The input port may conform to the composite-video or S-video standards.

Video compression-decompression hardware for video data.

Audio compression-decompression hardware for audio data.

A/D converter to convert the analog input video signals to digital form.

What is DV?

As you can guess, DV stands for "Digital Video". It is the new high resolution digital video standard.

DV is compressed at the camera, on the tape itself. The camcorder has the DV "codec" built in.

The DV spec is a 720x480 image size with a 5:1 compression. DV video information is carried in a nominal 25 megabit per second data stream. The color information is sampled at 4:1:1 for NTSC, and 4:2:0 for PAL.

Unlike MJPEG compressed video, DV video can't be scaled. You can't lower the screen size, change the screen size or data rate.

DV format is typically reckoned to be equal to or slightly better than Betacam SP or MII in terms of picture quality. Two types of DV camcorders, DVCAM and DVCPRO, are widely used in TV industry today.

However, for most of us, DV often refers to MiniDV actually. MiniDV is just the home level DV format. It is compressed to a constant throughput of 3,600 kilobytes per second. The video quality is not as good as Betacam, but much better than S-video.

What is FireWire?

Technically, it is the high speed, short distance data transfer protocol IEEE1394. Apple didn’t like the numbers and so called it "FireWire". Sony didn’t like it either, and so they called it "iLink". And they are all the same thing.

When the FireWire concept was first announced a few years ago, it was envisioned that it would become a new standard that would replace SCSI and link all our consumer electronics equipment and computers together. Now, the dust has settled and the hype has died down. The only application for FireWire that has actually come to fruition is for transferring digital video (DV) information directly from a camcorder (or VCR) to your hard drive.

What's the difference between DV and FireWire?

DV is the actual format of the video. 

FireWire is the port and protocol that lets you transfer the DV data to your computer. The full FireWire spec includes frame accurate device control and the ability to read and write the digital video.

When the video goes through the 1394 cable, into the capture card, and onto the hard drive, nothing is done to the video. It is a digital copy. It's identical to the original. And this is really nice.

How's the quality of DV?

The DV (MiniDV) spec is a 720x480 image size, at roughly a 5:1 compression. More accurately, it is compressed at a constant throughput of 3600 kilobytes per second which averages out to 5:1 compression. 

The images are crisp, bright and have excellent depth and contrast. In general, it's acceptable even in TV stations.

Best of all, the information is stored on the video tape in digital form, so it can be copied over and over without any loss.