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Pavtube Audio and Video Glossary

Advanced Audio Coding, or AAC, is a MPEG (Motion Pictures Experts Group) audio standard first adopted as part of the MPEG-2 family of standards. Like its predecessor, MP3, AAC is a Lossy Compression format capable of delivering relatively high quality at relatively low bitrates. There are actually two AAC specifications. This version is normally found in the MP4 Container, either with or without accompanying video.


There are a few stages in product development and alpha is one of these development stages. A product in alpha stage will satisfy all software requirements but will not have been completely tested or it could possibly be missing minor features. Products in alpha are considered to be in the first major stage of the so-called "release cycle" and that is where the name "alpha" comes from. Alpha is the first letter of the Greek alphabet. Products in alpha are generally considered to be only 35-40% complete and will be very buggy.


ATRAC stands for Adaptive Transform Acoustic Coding and ATRAC3 is an evolution of the earlier ATRAC1 system used with Sony's SDDS theater audio system and the MiniDisc format. ATRAC3 offers two separate modes, LP2 mode and LP4 mode. LP2 uses a uses a 132 kbit/s data rate, which is claimed to offer the same quality as MP3 audio at the same or similar bitrate, or so says Sony-funded tests of both audio formats.


ATRAC stands for Adaptive Transform Acoustic Coding and ATRAC3 is an evolution of the earlier ATRAC1 system used with Sony's SDDS theater audio system and the MiniDisc format. ATRAC3plus is an extension of the ATRAC3 format. The codec is used with Sony HiMD Walkman device , PlayStation 3 (PS3), PlayStation Portable (PSP), VAIO pocket and ATRAC CD players. It used four times the transform window of ATRAC3, stretching to 4096 samples with a signal split into 16 sub-bands pre bit allocation and MDCT processes.

AVC / H.264

MPEG-4 Part 10, also known as MPEG-4 AVC (Advanced Video Coding), is actually defined in an identical pair of standards maintained by different organizations, together known as the Joint Video Team (JVT). While MPEG-4 Part 10 is a ISO/IEC standard, it was developed in cooperation with the ITU, an organization heavily involved in broadcast television standards. Since the ITU designation for the standard is H.264, you may see MPEG-4 Part 10 video referred to as either AVC or H.264. Both are valid, and refer to the same standard.


AVI, which stands for Audio Video Interleave, is a Container format used by Microsoft's Video for Windows multimedia framework. Since it was developed for Windows 3.1 in 1992 it lacks some features found in newer containers like MPEG or MP4, but is still widely used by consumers and even supported by some standalone DVD players. Although still supported in Windows, and suitable for certain formats like DV, it's not a good general purpose container, and even Microsoft uses other containers for their own video formats.


AVS stands for Audio Video Standard. It's development was initiated by the People's Republic of China and its patents are 90% owned by Chinese companies. It is competing with H.264 / AAC to replace MPEG-2 video. AVS is a compression codec for both audio and video formats, and files containing AVS content carry the .avs extension (not to be confused with AviSynth scripts which carry the same extension).


B Frames can be found in MPEG video streams. They are not full frames and predicted by both the previous frame(s) and the next frames. Since they are not full frames, they use the least amount of space to store the frame data.


Bitrate refers to the size, over time, of a video or audio stream. Although most computer oriented applications measure bitrate in terms of binary kilobits and Megabits where 1kb (1 kilobit) = 1024 bits and 1Mb (1 Megabit) = 1024 kilobits, bitrate calculations use standard metric values for these prefixes, meaning 1kb = 1000b and 1Mb = 1000kb. Bitrate calculations are typically made in kilobits per second (kbps) or Megabits per second (Mbps)


Blu-ray is a name for a optical disc standard which uses blue-violet laser instead of red laser used in CDs and in DVDs. This allows manufacturers to store more data using the same amount of disc surface.In fact, Blu-ray got its name from the technology, basically the "Blu" is from blue-violet diode and the "ray" is from optical ray. The "e" was intentionally dropped so that the full term "Blu-ray" could be registered as a new trademark.


In a video program, a Caption is a textual representation of audio. Instead of just providing information on dialog, Caption supports the hearing impaired by also describing offscreen sounds and identifying the person speaking. This is also useful when a viewer would prefer, or needs to, mute a TV.


Capture refers to the process of either sampling an analog signal to a digiatal format or saving a digital stream being broadcast. Capture generally refers to muxed video and audio sources, but video-only, or more commonly audio-only, sources can be captured as well. In fact, the process of capturing both the video and audio for a particular source is actually two individual operations behind the scenes.


CAV stands for Constant Angular Velocity. It describes the motion of a body as it rotates at a constant angular velocity. It is one method used to read information from, and write to data discs. The rotation speed is kept constant. CAV ensures the same amount of information is provided in one disc rotation.

Digital Rights Management

DRM stands for Digital Rights Management and it is now (spring 2002) the hot topic among content owners and technology companies alike. DRM doesn't mean just basic copy-protection of digital content (like ebooks, MP3s or DivX videos), but it basically means full protection for digital content, ranging from delivery to end user's ways to use the content.


This is the process of creating a single frame from the two interlaced fields of a video frame. While interlaced video can look much better on a TV screen, on a monitor it can look rather bad.


Virtually all video and audio files have been encoded with some compression method, like DivX or MP3 and when we want to "open" these files, we need to decode that compression. Decoding basically means opening a compressed file, whether its done by playing the file or by storing it in an uncompressed format to HDD.


A new legal version of DivX video encoding technology, released by company called DivXNetworks. Originally the development of DivX codec went something like this: First there was Microsoft's MPEG-4 codec. Hackers made a more flexible version of it and started calling it DivX (note the smiley -- name was a pun towards failed DIVX pay-per-view format). Then more people got into DivX and there became a reason to build a compatible codec that wouldn't rely on stolen Microsoft code.

Dolby Digital

Dolby Digital (AC-3) is Dolby's third generation audio coding algorithm. It is a perceptual coding algorithm developed to allow the use of lower data rates with a minimum of perceived degration of sound quality.


FLV (Flash Video) "is a proprietary file format used to deliver video over the Internet using Adobe Flash Player (formerly known as Macromedia Flash Player) version 6, 7, 8, or 9. FLV content may also be embedded within SWF files. Notable users of the FLV format include YouTube, Google Video, Reuters.com, Yahoo! Video and MySpace. Flash Video is viewable on most operating systems, via the widely available Adobe Flash Player and web browser plugin, or one of several third-party programs such as Media Player Classic (with the ffdshow codecs installed), MPlayer, or VLC media player.


In order for Windows to play an AVI file its necessary to know what decoder on your computer should be used to render the video. AVI files all have a property called a FourCC, which consists of four letters, based on what kind of encoding is used. VfW decoders then register particular FourCCs with Windows, letting it know that they can Decode video in those formats. Some FourCCs correspond to a single application, meaning only one Codec can be used for decoding. Others, like DVSC for DV or any of the standard MPEG-4 FourCCs, can be decoded by a variety of VfW decoders that conform to those standards.


Defines how many pictures eg. frames one second of video or audio contains, normally used acronym for framerate is fps - frames per second. Human eye can't see picture changes after the framerate is more than ~24fps.


HD DVD is the "next generation DVD" and has been standardized by the DVD Forum as its official "next generation" format. Originally, the first "next gen format" to gain wide industry support was Blu-Ray, which was developed by Sony and Philips. However, due variety of reasons, Toshiba and NEC decided to bring their own format to the table, causing a similar situation to the next generation video format as the DVD-R and DVD+R caused to the recordable DVD media.

i Frame

In an MPEG video stream, an I Frame is a Full Frame. This Frame does not need any information from the frame before it or after it to be played back properly. While most of the time each I frame is the beginning of a new GOP, in some cases GOPs can contain multiple I frames.

Lossless Compression

A method of compression that will allow the complete original material to be recreated. For digital video, lossless compression techniques don’t do much to save disk space, so lossy compressions should be used. The files will still be significantly larger than standard compressed files, but good for use as intermediary files for editing and then compressing later. Mostly however, lossless compression methods are used mainly on audio files, to keep the highest quality possible.

Lossy Compression

A method of compression that sacrifices some data permanently to make the overall file size much shorter while attempting to preserve the most important data. It comes as a shock to people new to Digital Video to know that DVDs are actually under heavy compression. After using a lossy compression codec, there is no way to return to the exact source you had from your output file.


MPEG is short for Moving Pictures Expert Group which is a working group of ISO/IEC in charge of the development of standards for coded representation of digital audio and video. The first official MPEG meeting was in 1988 and as of 2008 the group has grown exponentially to include over 380 members every meeting.

MPEG Advanced Audio Coding

MPEG Advanced Audio Coding (AAC), otherwise known as MPEG-2 NBC (Non-Backward Compatible) is an audio standard allowing for more channels than MP2 or MP3 ( a full 48 channels compared to 5 for MP3). It can also handle higher frequencies than MP3, 96kHz compared to 48kHz. It has been tested at 96kbps to be of better quality then MP3 at 128kbps.


Audio and video compression format developed by MPEG group back in 1993. Official description: Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s. MPEG-1 is the video format that has had some extremely popular spin-offs and sideproducts, most notably MP3 and VideoCD.

MPEG-1 Audio Layer III/ MP3

MP3 stands for MPEG-1 Audio Layer III. It is not a separate format, but a part of MPEG-1 video encoding format, developed by MPEG group in early 1990's. Too often people refer MP3 as MPEG-3, which is incorrect, because such format doesn't even exist. MP3's bitrates vary from 8kbps (that is 8 kilobits per second, not kilobytes) to 320kbps. When MP3 phenomenon began in 1996, most of the audio files were encoded using 128kbps bitrate, which is still the most popular bitrate in the world -- although most of the people agree that by using slightly higher bitrates, like 192kbps or 256kbps, the audio quality can be compared with the CD quality.


MPEG-4 is one of the latest (audio and video) compression method standardized by MPEG group, designed specially for low-bandwidth (less than 1.5MBit/sec bitrate) video/audio encoding purposes. Probably the best-known MPEG-4 video encoders are called DivX and XviD, which both are nowadays fully standard-compliant MPEG-4 encoders.


Ogg is the umbrella for a group of several related multimedia and signal processing projects that are open source and royalty free. Development of these projects is controlled by Xiph.org.


Samplerate refers to the samping Frequency of an analog to digital conversion (or analog capture). This literally means how frequently the analog source is sampled. Samplerate is measured in samples per second, where 1 Sample per second is equivalent to a sampling frequency of 1Hz.


VOB stands for DVD Video Object. It is basically one of the core files found on DVD-Video discs and contains the actual movie data. Basically VOB file is just a basic MPEG-2 system stream -- meaning that it is a file that contains multiplexed MPEG-2 video stream, audio streams (normally AC3 and DTS formats) and subtitle streams.


Established in December 1998, the 3rd Generation Partnership Project (3GPP) consists of telecommunications standards bodies collaborating to make a third generation (3G) mobile phone system specification for global use. The organizations are known as the "Organizational Partners" of the project. The project was established after the signing of the "The 3rd Generation Partnership Project Agreement".


1080i refers to an interlaced HDTV signal with 1080 horizontal lines and an Aspect ratio of 16:9 (1.78:1). All major HDTV broadcasting standards include a 1080i format which has a Resolution of 1920x1080, however there are other formats, including HDV and AVCHD for camcorders, which utilize 1080i images with a resolution of 1440x1080. Confusing matters even further, a 4:3 (1.33:1) image broadcast in 1080i (1920x1080) uses the center 1440 Pixels for the image, with 240 pixel wide pillarbox borders on each side.


1080p refers to a progressive HDTV signal with 1080 horizontal lines and an Aspect Ratio of 16:9 (1.78:1). All major HDTV broadcasting standards include a 1080i format which has a resolution of 1920x1080, but the progressive HDTV broadcast standards in place right now only allow a resolution of 1280x720 (720p). Currently the only applications using 1080p signals are Blu-ray and HD DVD.

2009 - 02 -17