AAC
Advanced audio coding. An audio-encoding standard for MPEG-2 that is not backward-compatible with MPEG-1 audio.

AC3
 AC3 or the .ac3 file is a Dolby Digital audio file. Dolby's best-known digital system, is used to provide multichannel surround sound in cinemas from 35 mm film, and in the home from laser discs, DVDs, and digital broadcast television, cable, and satellite systems. It enables the transmission and storage of up to five full-range audio channels, plus a low-frequency effects channel (LFE), in less space than is required for just one linear PCM-coded channel on a compact disc.

AdDetective™
Is the VideoReDo Commercial Detection feature that cuts advertisements from your videos. AdDetective will scan your files for likely places where advertisements start and end. You can preview and change AdDetective recommendations before editing, or let VideoReDo Plus do the job automatically.

Aliasing
A distortion (artifact) in the reproduction of digital audio or video that results when the signal frequency is more than twice the sampling frequency. The resolution is insufficient to distinguish between alternate reconstructions of the waveform, thus admitting additional noise that was not present in the original signal.

Anamorphic
Process where a “wide” video image (typically in a 16:9 widescreen format) is compressed or squeezed horizontally to fit a more narrow video display standard but expands to full size when played over a wide video display.

Letterboxing an image enables the viewer to see the entire widescreen presentation of a movie as it was intended and as it was shown in the theater. However, in order to fit a “wide” image in a “narrow” television, the wide image must be centered in the screen with black bars above and below it (in order to fit a wide image in a narrow screen, the width must match the width of the narrow display so the height of the image is necessarily less than that of the more narrow and square video display). While this method allows the user to see the entire image as it was meant to be seen (narrow 4:3 aspect ratio television sets normally show pan & scan movies), the image loses some horizontal resolution to the black bars.

While not much can be done about this on standard 4:3 televisions, there are wider 16:9 displays, which can show an entire movie image with no bars thus allowing the picture to fill the screen. To take advantage of this, a movie can be distributed in a squeezed anamorphic format without black bars. On a more square 4:3 television this results in an image which seems tall and pinched with actors looking too narrow and objects distorted. However, when played on a widescreen display, the picture is stretched out to its proper width resulting in a widescreen image with no bars and the maximum possible resolution. This technique is being used primarily with DVDs to provide superior quality video to users of widescreen televisions. DVDs featuring this anamorphic version allow a user to watch the image in a letterboxed or pan & scan format on their traditional more square 4:3 televisions when this is selected while allowing users with widescreen televisions to enjoy the full benefit of their displays.

Antialiasing
Smoothing or reducing disturbing picture effects. By means of calculation of intermediate values along the sharp edges of types and graphics, these edges can be smoothed out, thus generating a smoother picture. The pixel structure along tilted or bent edges is mixed with the surrounding colors. When creating DVD Menu text, antialiasing must not be used.

Artifact
An unnatural effect not present in the original video or audio, produced by an external agent or action. Artifacts can be caused by many factors, including digital compression, film-to-video transfer, transmission errors, data readout errors, electrical interference, analog signal noise, and analog signal crosstalk. Most artifacts attributed to the digital compression of DVD are in fact from other sources. Digital compression artifacts will always occur in the same place and in the same way. Possible MPEG artifacts are mosquitoes, blocking, and video noise.

Aspect Ratio
The width-to-height ratio of an image. A 4:3 aspect ratio means the horizontal size is a third again wider than the vertical size. Standard television ratio is 4:3 (or 1.33:1). Widescreen DVD and HTDV aspect ratio is 16:9 (or 1.78:1). Common film aspect ratios are 1.85:1 and 2.35:1. Aspect ratios normalized to a height of 1 are often abbreviated by leaving off the :1.
 
ATSC
The Advanced Television Systems Committee, Inc., is an international, non-profit organization developing voluntary standards for digital television. Specifically, ATSC is working to coordinate television standards among different communications media focusing on digital television, interactive systems, and broadband multimedia communications. ATSC Digital TV Standards include digital high definition television (HDTV), standard definition television (SDTV), data broadcasting, multichannel surround-sound audio, and satellite direct-to-home broadcasting.
http://www.atsc.org/aboutatsc.html

Author
To format video into a form ready to burn onto a recordable disc or to stream onto the Internet. VCD, SVCD and DVD Author is to format video into its standard file structure and also add optional menus, chapters, audio tracks, subtitles, slideshows and much more.

AVI
Audio Video Interleaved - A multimedia file format for storing sound and moving pictures in RIFF format developed by Microsoft. An AVI file can use different codecs and formats so there is no set format for an AVI file unlike for example standard VCD video which sets a standard for resolution, bitrates, and codecs used.

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