VIDEO RECORDING AND STORAGE SYSTEM

Pertemuan 9

Matakuliah : O0382 – Dasar-dasar Produksi Siaran TelevisiTahun : 2010

Tape and Disk-Based Recording Systems (1/5)

Tape-based recording system uses videotape for the recording, storage, and playback of video and audio information.Disk-based recording system uses either large-capacity computer hard disks or read/ write optical discs. This section will discuss aspects on recording systems: (1) analog and digital systems, (2) linear and nonlinear systems, (3) composite and component systems, and (4) compression.

Analog and digital systemsThe difference between analog and digital recording system is on the way they store the recording. In analog recording systems, it records video and audio signal as created and processed by the video source; in digital recording systems, it stores not the video nor the audio signals, but the data.

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Tape and Disk-Based Recording Systems (2/5)

Linear and nonlinear systemsThe differences between linear and nonlinear recording systems are on the way the information are recorded and accessed.Linear systems apply to all tape-based systems. Linear system records the information serially; therefore, the data retrieval should be in series.Nonlinear systems apply to all disk-based systems. Nonlinear system records the information randomly; therefore, the data retrieval can be conducted in random access. Nonlinear or random access is important when editing as the data can be recalled instantaneously.

Composite and component systemsThe video recording in composite and component systems differs in production application. Analog and digital systems can treat their signal in four ways: (1) composite, (2) Y/C component, (3)Y/ color difference component, and (4) RGB component.

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Tape and Disk-Based Recording Systems (3/5)Composite system

The analog composite system combines the color (C, or chrominance) and brightness (Y, or luminance) information into a single (composite) signal. Composite signal is also called NTSC system since it was standardized by the NTSC (National Television System Committee). NTSC system is different from worldwide system (eg.: European PAL). The major disadvantage of composite signal is that there can be interference between chrominance and luminance that gets worse; and more noticeable with each videotape generation.

Y/C component systemIn the analog Y/C component system, the Y and C are kept

separate during the encoding (write) and decoding (read) process. During recording process, both signals are combined and occupy the same track on the videotape. The advantage of Y/C component system is that the system produces higher-quality pictures that will suffer less in subsequent tape generations than do NTSC tapes.

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Tape and Disk-Based Recording Systems (4/5)

Y/color difference component systemIn the analog Y/color difference component system; the

luminance signal, the red signal minus its luminance (R-Y), and the blue signal minus its luminance (B-Y) are transported and stored as three separate signals.

RGB component systemIn analog RGB component system, the red, greed, and

blue signals are kept separate and treated as separate component throughout the recording and storage process.

SamplingThe 4:1:1 over 4:2:2 sampling ratios in all forms of video

recording mean in the digitizing process, the C (color) signals are each sampled at one-fourth for 4:1:1 and one-half for 4:2:2 the sampling frequency of the Y (luminance) signal.

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Tape and Disk-Based Recording Systems (5/5)The luminance signal receives such privileged treatment because it is a major contributor to the sharpness of the picture. As for color signal, it produces good color for most normal production requirements.If high-quality color that can stand up to a variety of special effects such as various blue-screen or chrome-key effects is required, then the equipment that uses a higher sampling ratio is needed.Finally, we must understand that in comparison, the video signal of the NTSC composite system is of lower quality than that of the Y/C component system which is somewhat inferior to the Y/color difference component system or the RGB component system.

CompressionIn compression, there are (1) lossless compression which

means rearranging data so that it takes up less space, and (2) lossy compression which means throwing away the unnecessary items so that it can use much smaller suitcase. The 2 (two) compression standards are JPEG for compressing styli images and MPEG for compressing moving images.

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Tape-Based Recording and Storage Systems (1/5)This part will discuss 4 (four) aspects on tape-based recording and storage systems: (1) how videotape recording works, (2) the operational VTR controls, (3) their electronic features and how they function, and (4) the major analog and digital VTR’s presently in use.

How videotape recording (VTR) worksVTR is any electronic recording device that records video and audio signals in videotape for later playback or postproduction editing purpose. There are 6 (six) components that take part in videotape recording process: (1) record/ playback heads, (2) videotape tracks, (3) video track that contain the picture information, (4) audio tracks that contain all sound information, (5) control track that controls the videotape and rotation speed of the VTR speed, (6) digital recording systems that translate the video signal into digital form and record it as digital information. The final record is no longer a video signal but on/off pulses that are usually coded as 0’s and 1’s.

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Tape-Based Recording and Storage Systems (2/5)

Operational VTR controlsThe most basic functions on VTR control are: (1) play, (2) stop, (3) record, (4) fast-forward, (5) rewind, (6) eject buttons, and (7) audio volume control. The more sophisticated VTR has additional functions: (1) standby, (2) pause or still, (3) search or shuttle, (4) tracking, and (5) audio controls.

Electronic controlsThe major electronic features that is important to understand to operate VTR are: (1) input and output jack, (2) the time base corrector, (3) the frame store synchronizer, (4) the automatic moisture shutdown.

Major Analog Videotape RecordersThe more popular tape-based analog VTRs found in many large and small television stations and production centers include Betacam SP, S-VHS, Hi8, and VHS. In the next slide, there will be breakdown of each characteristics of the major analog videotape recorders.

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Tape-Based Recording and Storage Systems (3/5)Analog VTR Table

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System Recording Format Cassette Production Characteristics

Betacam SP Y/C componentY/color difference

½ inch (12.65mm) High quality, standard high-end analog recording system in studio VTRs and camcorders

S-VHS Y/C component, but actually recorded as a composite signal

½ inch (12.65mm) Good quality, downward compatible with VHS

Hi8 Y/C componet 8mm (just slightly more than ¼ inch)

Good first-generation quality, must be dubbed up to a higher quality format for extensive postproduction editing

VHS NTSC composite ½ inch (12.65 mm)

Quality not good enough for broadcast applications or extensive postproduction, used extensively in off-line work.

Tape-Based Recording and Storage Systems (4/5)

Major Digital Videotape RecordersThe advantages of digital VTRs are: More compact and even less expensive models produce high-quality

pictures and sound that maintain their quality through repeated dubs; Does not need to be converted for computer storage on hard disk for

nonlinear editing and special effect manipulation; Easy to operate

The major systems on major digital videotape recorders are: (1) DVCPRO, (2) DVCam, (3) DV, and (4) Digital Betacam. In the next slide there will be description on each characteristic of those systems.

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Tape-Based Recording and Storage Systems (5/5)Digital Classification

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Sistem Recording Format Sampling Ratio

Cassette Production Characteristics

D-1 RGB componentY/color difference component

4:4:44:2:2

¾ inch (19mm)

Superior video and audio quality, still in use in some postproduction houses for building complex effects, tolerates many dubs with no quality loss

D-2 NTSC composite ¾ inch (19mm)

Can be integrated with analog equipment, no compression

D-3 NTSC composite ½ inch (12.65mm)

Same as D-2 except that it has a smaller tape size. Can record up to 4 hours of programming, no compression

D-5 RGB component 4:2:2 ¼ inch (6.35mm)

All four audio tracks are high-fidelity and reproduce CD-quality sound. No compression in standard TV, compressed in HDTV

D-7/ DVCPRO

Y/color difference component

4:1:1 ½ inch (12.65mm)

Excellent quality, intraframe compression. The higher-quality DVCPRO 50 uses 4:2:2 sampling when interfaced.

D-9/ Digital-S

Y/color difference component

4:2:2 ½ inch (12.65mm)

Compatible with other digital systems, plays back S-VHS tapes, intraframe compression.

Disk-Based Recording and Storage Systems (1/3)

The basis for nonlinear production editing is the development of large-capacity hard disks or read/write optical discs with fast access times. The following will be the overview on all disk-based recording and storage system related aspects: (1) hard disk systems, (2) read/ write optical discs, and (3) methods of data transfer.

Hard Disk SystemsThese systems include:Large capacity hard disks

The accelerated hard-drive speeds and highly efficient compression techniques makes it easier to store and retrieve digital video and audio information for postproduction editing.Portable hard disks

Also called fieldpacks, are designed to be docked with ENG/ EFP cameras. It has the size of a dockable VTR that can hold two hours digital video and audio information.

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Disk-Based Recording and Storage Systems (2/3)

Electronic still store (ESS) systemsESS is a slide that stores any frame from various video sources (camera, videotape, or computer) and those frames can be stored in a hard disk. A tiny 2-inch floppy can hold up to 200 frames.

Digital video cart machinesVideo cart machines record, manage, and automatically play back a great variety of videocassettes. However, this huge machine has been replaced by large-capacity computer systems.

Read/ Write Optical DiscsThis system enables the recording and playing back a great amount of digital information. For this purpose, we can use CD-Rs (compact disc recordable) for storing information, and CD-RWs (digital versatile disc-read/write) for recording and playing back short or long video sequences.

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Disk-Based Recording and Storage Systems (3/3)

The main advantage of read/write optical disc is its extremely fast access time; and the ability to precisely locate, cue, and play a certain scene in a second.

Data TransferThere is a need to transfer the data recorded by the digital camcorder to a temporary digital storage device. FireWire (from Apple) and i-link (from Sony) are the data transfer system that able to transfer digital data from storage (like camcorder VTR) to a desktop computer.Similar to streaming audio, streaming video is an internet delivery system that sends compressed data as a continuous stream and it can update video continuously while you are watching the video.

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