Glossary

Representation of an image width to its height. A general notation is the form of X:Y where X represent the image width and Y represent the image height.While there are several video standards that are currently used in video applications, it is necessary to keep aspect ratio stable when converting ...

Rate of bits transmitted over a particular period of time on a specific channel.In video coding applications, video bit rate is determined by the number of the used bits per one second.For example: 1Mbps = 1Megabit (1 Million bits) per second.

  CBR is a technique for encoding voice and video which forces the output bitstream to stay within a specific bitrate constraint in a short timeframe, which is usually set to a single second. This reduces the flexibility of the encoding process to invest more bits in complex segments. CBR ...

Common Intermediate Format: 352 × 288 pixelsA standard video format used in video conferencing. Also known as "SD" (Standard Definition).

Color sampling, or Chroma sub-sampling, is the practice of encoding images by reducing the input resolution for the chroma information. It is used in many video encoding schemes — both analog and digital.Since the human visual system is much more sensitive to variations in brightness (knows as Luma component) than ...

A color space describes the range of colors, or gamut, that a certain device or standard can support. For instance, the range a camera can capture, a monitor can display or a standard can encode.A color space covers a subset of the entire color spectrum. Some color spaces contain more ...

Far End Camera Control is the means by which a user in a video conference call can gain control of a PTZ camera on a remote location which is also participating in the conference call.Far End Camera Control specifications usually offer the following set of capabilities:Ability to select between different ...

Field of view usually refers to the horizontal field of view of the camera on a video conferencing system. Field of view is the viewing angle the camera will provide - the larger the viewing angle the more you will see from the room/location you are capturing with the camera. ...

Forward Error Correction (FEC) is a type of correction code, which allows the receiver to compensate for loss packets without requiring any information to be sent in real-time by the sender.According to the FEC mechanism, the sender of the media stream sends redundant data as part of the stream. This ...

FPS stands for Frames Per Second. It indicates the rate of frames used in one second of video stream. The most common frame rate today for video communiation is 30 fps.

A term defining the size of the basic element of video content – the frame.Frame resolution describes the number of pixels on the horizontal and vertical axis of a video frame.There are several predefined popular acronyms for frame resolutions: CIF – 352×288, 4CIF – 704×576, D1 – 720×480 (NTSC) or ...

A Gateway (GW) in telecommunications context is a boarder element that bridges between one network to another translating between transmission formats and communication procedures (protocols). A typical GW will bridge between an IP based network to a Public Switched Telephone Network (PSTN) or between one IP based network to another ...

H.264 (also known as MPEG-4 AVC) is currently the de-facto leading standard for video compression. It was standardized in 2003 in a joint effort by the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG), known as the Joint Video Team (JVT).H.264 is used in ...

An Inter Frame (known also as an P-Frame) is a frame that is dependent on other frames, either Intra frames or Inter frames. To decode an Inter frame previous frames that it depends on are required.

In a coded video stream there are different frame types, according to their level of dependency.An Intra Frame (known also as an I-Frame) is a frame that is independent. As it is not dependent on any other frame in the stream, it can be decoded with no need of any ...

A term used to describe the variation in packet delay. In packet switch applications, where data is carrying over network packets, there is a variance in the packet arrival timing. In order to overcome this variance and to provide a smooth usage of the received packets, a delay buffer is ...

A term used to refer to the relative timing of audio and video portions during playback. In general, it used to describe the matching of lip movements with voice. Generally, human perception is sensitive to non synchronized audio and video with a relative phase of ~100 msec. In contrast, there ...

A term used to describe a compression method where the compressed data cannot be reconstructed exactly as the original form. This type of compression is mainly used in visual and audio applications where a partial loss of data is acceptable by the human visual and hearing systems. As opposed to ...

In video coding, frames are split into macroblocks (MBs), where each macroblock is in the size of 16x16 pixels. Each macroblock in a frame can have a different quantization level thus allowing the codec rate control engine to spread the coded bits relative to the texture complexity.

MTU stands for "Maximum Transmission Unit". It is the largest size of a packet that can be sent over an IP network without splitting it into multiple packets.When data is sent over UDP (which is the case when sending voice and video packets using RTP), there is a need to ...

NetSense is RADVISION's bandwidth estimation and adaptation technology, enabling a high quality of experience even on unmanaged networks. NetSense estimates the available bandwidth in a network path, based on the delay in the video stream, therefore allowing to detect congestion in the network before it escalates to packet loss and ...

Packets are units of information sent across a packet switched network from their source address to a destination. Packet loss occurs when one or more packets fail to reach their destination. On network protocols such as UDP that provide no recovery mechanism for packet loss, applications should handle that error ...

A term used to describe playback video on a PAL TV.In general, PAL refers to standard definition (SD) video with vertical resolution of up to 576 pixels and horizontal resolution of up to 720 pixels. PAL frame rate is 25 fps.PAL broadcasting can be found in Western Europe countries, Australia, ...

PSNR, an abbreviation of Peak Signal-to-Noise Ratio, a term used to describe objectively the quality of data, which is the result of decompressing encoded data. For example, the quality of a certain image in a video bit stream. PSNR is the ratio between the maximum possible power of a signal ...

Some cameras are fixed while others can move around. Those that can move around are called “PTZ cameras”, or “Pan-Tilt-Zoom Cameras”, as they can pan and tilt (move up and down and to the sides) and they can zoom in and out – mechanically. PTZ cameras usually rely on motors ...

Quarter CIF: 176x44 pixelsA standard video format used in mobile video conferencing (3G-324M), where the phone’s processing power and power consumption (and the display) limit the video resolution. QCIF also requires only a quarter of the transmission bandwidth required for CIF video resolution.

"Talking heads" is a term usually used to define a point-to-point video calling scenario, where the video displayed shows both people on from the shoulders and up. At its core, it is the most basic layout for video telephony, often considered as not compelling enough for more advanced video calling ...

Transcoding is the conversion of one transmission format into another using various algorithms to achieve wider support of formats at different quality levels.In the context of video communications, transcoding will usually take place between video codec formats and voice codec formats.The operation of transcoding brings with it several challenges:Transcoding increaes ...

Transrating means changing the bitrate (bandwidth) of a stream by means of processing. For instance, processing an input video stream of 1Mbps so that the output stream is 256Kbps only. Transrating can increase or decrease the bitrate, and usually involves changing the encoding parameters (usually quantization).See also: Transcoding

  VBR is a technique of encoding voice and video which allows the output bitstream to vary in the amount of bits per a given amount of time. This allows higher bitrates to be allocated to segments in the bitstream that are more complex than others. VBR is usually used ...

The big challenge in most video applications is to provide the highest video quality with a minimum cost of bit rate. As a result of lossy compression techniques, non optimized network conditions and other application restrictions, video quality is affected and quality of service may reduce. Video artifacts may be ...

Software or hardware device that enables video decompression. In general, a video decoder is used to reconstruct the video content from compressed data into a visible displayed format. For real time streaming network applications, the decoder is used to convert video packets sent over the network into video frames which ...

Software or hardware device that enables video compression. Generally, compression is used to reduce the size of the visual content, either for storage purposes or for streaming over a network channel (reduce bit rate). Video encoder performance and quality is being determined by the encoder complexitySee also: Video Decoder

Video Fast Update (VFU) is a mechanism in which a receiver requests a "refresh" from the sender, in case the video received is suspected to be corrupted (for instance, in case of a packet loss).In case of a VFU request, the sender will send a new Intra Frame, to serve ...