| V |
- VBR (Variable Bit Rate)
- A more efficient method (as opposed to FBR) of encoding a digital audio or video stream in order to reduce it’s subsequent file size. The bit rate of an encoded audio/video file is the number of bits (binary digits - 0s or 1s) that are required to store 1 second of program.
- In audio, an MP3 file at 128kbps requires 128,000 (ish!) bits to store 1 second of audio. Using psychoacoustic algorithms, a Variable Bit Rate encoder varys the bit rate depending on how much information is needed to only store the most audible portion of the signal from moment to moment. Since silence doesn’t contain very much information, a VBR encoder just stores a code meaning “'x' seconds of silence” rather than storing thousands of zeros.
- In video, a VBR encoder uses algorithms which only store the changes from frame to frame rather than the entire video scene.
- VERTICAL INTERVAL SWITCHING
- In practice, randomly switching from one video signal to another, will often result in a jump in the picture upon playback. The problem is compounded when the tape is copied. To avoid this problem, switching is best performed on synchronized signals during the vertical blanking retrace period, known also as the vertical interval. This allows complete replacement of one whole frame by a second whole frame resulting in a very smooth on-screen switch.
- VHS (Video Home System)
- Consumer videocassette record/playback tape format using 1/2" wide magnetic tape. VHS is the predominate consumer VCR format today, producing about 240 lines of horizontal video resolution compared to standard NTSC television broadcast signals of about 330 lines. The most common home VCR format in the U.S.
Popular rumor has it that Sony originally developed the VHS format concurrently with the Beta format in the early 1970s. Deciding to market the higher quality Betamax system, they sold the rights to the VHS format to JVC in order to recoup some development costs. The rest is history.
- VHS-C (VHS-Compact)
- A miniature, electronically identical version of the VHS tape format utilizing smaller videocassettes that may also be played on standard VHS machines with the assistance of an adapter cartridge. This format was introduced in order to compete with Sony’s 8mm camcorder format but with reduced recording time.
- VIDEO BANDWIDTH
- The range between the lowest and highest signal frequency of a given video signal. In general, the higher the video bandwidth, the better the quality of the picture. Video bandwidths used in studio work typically vary between 3 and 12 MHz. Consumer VCRs are generally capable of 3-5.5 MHz.
- VIDEO CAMERA
- A camera which contains an electronic image sensor rather than photographic film. The lens focuses an image on an electronic tube or CCD chip.
A camera has electronic circuitry which generates color and sync pulses. Most portable consumer camcorders are equipped with a full complement of audio circuitry, e.g., microphone, audio amplifier and additional audio electronics. In order to obtain better quality images, a professional camera has three tubes or a triple CCD system, one for each primary color. Most professional cameras have a genlock input, which allows the camera to be synchronized to an external source. Some cameras also include basic character generators for titling purposes.
- VIDEO CD
- Format that allows the viewing of MPEG-1 (also known as the ISO IEC 11172 compression standard) video on CD-ROM. It allows for more than an hour of compressed video and compressed, hi-fi quality audio. The whole point of VideoCD is cross-platform compatibility. The discs should work on suitably equipped PCs, Macs, dedicated VideoCD players, and CD-I systems. The VideoCD specification is based on the White Book standard.
- VIDEO ENHANCER
- A general term used to describe a device used to correct video image problems.
- VIDEO GAIN
- The nominal composite video signal level is 1V (volt). At this level, a fully saturated image is transmitted and boosting the signal offers no advantage. Most video equipment is designed to output the same 1V level video signal. In cases where the signal level has been reduced, such as after a long cable run, an amplifier with video gain may be employed to restore the proper level.
- VIDEO MIXER
- A device used to combine video signals from two or more sources. Inputs are synchronized, then mixed along with various special effects patterns and shapes. A video mixer usually generates sync signals allowing genlocking of additional video sources to the first source.
- VIDEO PRINTER
- A special device used to capture a single frame of video to create a hard copy print.
- VIDEO PROJECTOR
- A display device which projects a video or computer image onto a large screen. The classic video projector has three primary color video tubes which converge on-screen to create the full color image. Single tube projectors eliminate convergence problems but compared to three tube systems, project a relatively lower quality image.
- VIDEO WALL
- A large array of several monitors, placed close to one another in the shape of a video screen or “wall.” Each monitor is fed only part of the original video image by using a video-wall generating unit. This device is a digitally-based processor which converts the original analog video signal to digital, rescans, resamples and generates several individual analog video outputs for driving each array monitor separately. When viewed from a distance, the effect can be very dramatic.
- VITC (Vertical Interval Time Code)
- SMPTE time code standard for recording onto videotape. By inserting the digital address for each video frame into the vertical blanking interval of the video signal, it remains invisible on-screen yet is easily retrieved, even when a helical scanning VCR is in pause mode.
 |
We invite the Production Sound and Multimedia communities to link to this web site.
| Copyright ©2008 |