Glossary

A list of video/audio terms and definitions to help you become more familiar with the terminology used in video/audio software and devices.

AAC
Advanced Audio Coding (AAC), also known as MPEG-2 Part 7, is a digital audio encoding and lossy compression format. AAC delivers high quality audio at a lower bitrate compared to other audio encoding standards like ISO/MPEG Audio Layer-3; MP3.

AC3
AC3, also known as Dolby Digital, is a perceptual digital audio coding technique that reduces the amount of data needed to produce high-quality sound. Perceptual digital audio coding takes advantage of the fact that the human ear screens out a certain amount of sound that is perceived as noise. Reducing, eliminating, or masking this noise significantly reduces the amount of data that needs to be provided. AC3 is the sound format for digital television (DTV), digital versatile discs (DVDs), high definition television (HDTV), and digital cable and satellite transmissions.

Audio Codec
Codec stands for Compressor and Decompressor. A software component which compresses and decompresses audio.

AVI Format (AVI)
Audio Video Interleave (AVI) is a file format defined by Microsoft. It is the most common format for audio/video data on PCs. AVI files can have one or more video streams and one or more audio streams. The video and audio streams can be compressed using various compressors. Each compression has one or more possible decompressors. This means that two files are not similar just because they have the same extension. You might be able to play one AVI file (because you have its decompressors) but you might not be able to play another (because you do not have its decompressors). Or you might have the audio decompressor but not the video decompressor. (In this case, you would hear the audio, but not the video).

AVC
Advanced Video Coding (AVC) is a digital video codec standard which is noted for achieving very high data compression. It is common to call the standard H.264/AVC (or AVC/H.264 or H.264/MPEG-4 AVC or MPEG-4/H.264 AVC).

B (Bi-directional) frames
B frames are encoded using both previous and next frames as reference and are better compressed than P frames and I frames.

Codec
A codec is technology (software or hardware) that compress and decompress data. By using codecs for compressing audio and video data into smaller packets that do not consume as much hard disk space or network bandwidth, multimedia applications can provide richer and fuller content.

Compressor
Also known as an encoder, this is a module or algorithm to compress data. Playing that data back requires a decompressor, or decoder.

Decoder
Also known as a decompressor, this is a module or algorithm to decompress data.

Decompressor
Also known as a decoder, this is a module or algorithm to decompress data.

DVSD AVI Format (AVI)
Standard digital video (DV) audio/video format encapsulated in an AVI encoded stream.

DVSD OGG Format (OGG)
Standard digital video (DV) audio/video format encapsulated in an OGG-encoded stream.

Encoder
Also known as a compressor, this is a module or algorithm to compress data. Playing that data back requires a decompressor, or decoder.

H.263
H.263 is an ITU standard, designed for low bitrate communications such as video-conferencing and video-telephony applications. At the same time it can be used for a wide range of bitrates and not just low bitrates.

H.264
H.264 is a high quality video compression algorithm and is suited for all types of applications with different ranges of bit rates. H.264 compressed video data can be stored inside AVI or OGG files with the option of saving the file with or without the audio data.

iCompress™
iCompress™ is a collection of technologies from LEAD's software development and research labs that have special relevance to digital imaging and multimedia application development software for both the enterprise and end users.  These technologies represent 15 years of development in the programming tools marketplace. 

I (Intraframe) frames
I frames are encoded without reference to another frame, providing support for random access. See also P frames and B frames.

Interframe
Interframe compressors compress the differences between adjacent frames. Generally, the interframe algorithms provide higher compression ratios than intraframe algorithms. The trade-off to the higher compression ratios of interframe compressions is speed. Inter-frame compressors usually can not compress video in real time, while intraframe compression can do real time compression. LEAD offers the following interframe compressors: H.264, H.263 and MPEG/MPEG-2

Intraframe
Each transmitted video image or sample is compressed independently. LEAD offers the following intraframe compressors: MCMP/MJPEG, MJPEG2000 and MCMW.

LEAD MCMW Encoder
This encoder is fast, and good for high compression capture. At high compression, the image becomes blurry rather than blocky. This is a proprietary encoder developed by LEAD Technologies, Inc.

Lossless compression
Compression techniques can be categorized into two groups, lossless and lossy. When data has been compressed using a lossless compression technique, the result of the decompression will be bit for bit exactly the same as the original data before compression. Generally, lossless compression can not achieve anywhere near the compression ratios of that of lossy compression. The following LEAD codecs offer lossless data compression: MJPEG2000 and MCMW.

Lossy compression
Compression techniques can be categorized into two groups, lossless and lossy. When data is compressed using a lossy compression technique, the result of the decompression will not exactly match the original. Most lossy compression techniques allow you to control how much loss (quality or q-factor). The following LEAD codecs offer lossy compression: H.264, H.263, MPEG/MPEG-2, MCMP/MJPEG, MJPEG2000 and MCMW

MP4 (ISO/IES 14496-14:2003) Format
MP4 is a multimedia format (container) that contains multiplexed audio and video streams. MP4 supports AAC encoded audio stream and H.264 or MPEG-4 encoded video stream.

MPEG (Moving Picture Experts Group)
The Moving Picture Experts Group sets the international standards for digitally encoding movies and sound. They have several standards for audio and/or video formats.

MPEG-2
MPEG-2 is a high quality video compression and is primarily targeted for applications that require higher bitrates or high bandwidth usage, most commonly DVD videos, Super VCD (SVCD), box top DVR's and digital television.

MPEG-4
Introduced in 1998, MPEG-4 is the designation for a group of audio and video coding standards and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG). The primary uses for the MPEG-4 standard are web (streaming media) and CD distribution, conversational (videophone), and broadcast television.

OGG Format (OGG)
OGG is the name of Xiph.org's container format for audio, video, and metadata. Its default audio compressor is called Vorbis. Vorbis compression offers better quality than MP3 and yields a higher compression ratio. Ogg Vorbis is different from other formats because it is completely free, open, and unpatented. The video and audio streams can be compressed using various compressors. Each compression has one or more possible decompressors. This means that two files are not similar just because they have the same extension. You might be able to play one OGG file (because you have its decompressors) but you might not be able to play another (because you do not have its decompressors). Or you might have the audio decompressor but not the video decompressor. (In this case, you would hear the audio, but not the video).

P (Predictive) frames
P frames are encoded using the previous frame as reference. P frames are more highly compressed than I frames.

SAD HADAMAR
SAD HADAMARD is a calculation of the sum of absolute difference indirectly by applying HADAMARD transform to the block before calculating SAD increasing the compression ratio. The following LEAD codecs make use of SAD HADAMAR: H264

Temporal compression
Temporal compression is the process of only encoding the difference between successive frames, instead of the frames themselves. Any given frame is constructed from the prediction from a previous frame and may be used to predict the next frame. The following LEAD codecs make use of temporal compression: H264

Wavelet
Wavelet transforms are mathematical formulas that represent complex structures in an image, thereby compressing an extremely large amount of image data into a relatively small amount of compressed data. This compression technique allows applications to save compressed imagesor videos with higher compression ratios and better quality as compared to any other intraframe compression technique. The following LEAD codecs make use of wavelet compression: H.264, H.263, MJPEG2000 and MCMW

Video Codec
Software component which compresses and decompresses video. Codec stands for Compressor and Decompressor.

Vorbis
Vorbis is an open and free audio compression (codec) project from the Xiph.org Foundation. It is frequently used in conjunction with the Ogg container and is then called Ogg Vorbis.

iCompress™ is a trademark of LEAD Technologies, Inc.