Video

Video (from Latin, "I see") is the technology of processing electronic signals for representing moving pictures.

Characteristics of video stream

Number of frames per second

Number of frames per second (FPS or frame rate): Can be from 6-8 fps for old mechanical cameras to 120 fps and more for new professional cameras. For PAL (Europe) and SECAM (France) standards it's 25 fps, for NTSC (North America) - 30 fps. Minimum number of frames for illusion of moving picture is about 10 fps.

Related Topics:
FPS - PAL - SECAM - NTSC

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Interlacing

Video can be interlaced or progressive. Interlacing was originally conceived as a way to achieve good visual quality within the limitations of a narrow bandwidth. Every frame of interlaced video has 2 fields. One field contains only the odd-numbered lines (forming the odd field), and the next contains only even-numbered lines (forming the even field). NTSC, PAL and SECAM are interlaced formats. Interlacing commonly noted as i character near resolution (e.g. 576i50).

Related Topics:
Interlaced - Progressive

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In progressive scan systems, each frame is complete (i.e. includes all scan lines). The result is a much higher perceived resolution.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A procedure known as deinterlacing can be used for converting an interlaced stream (analog, DVD, satellite) for progressive devices (TFT TV-sets, projectors, Plasma panels). Any deinterlacing inevitably decreases video quality.

Related Topics:
Deinterlacing - Video quality

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Video resolution

Size of video image in pixels (for digital video) or lines (for analog video). Standard-definition television (SDTV) refer to 640×480i60 (NTSC) and 720×576i50 (PAL, SECAM) resolution. New High-definition television (HDTV) define resolutions up to 1920×1080i50.

Related Topics:
Pixels - SDTV - HDTV

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Video resolution for 3D-video measured in voxels (volume element, representing a value in three dimensional space). For example 512×512×512 voxels resolution now used for simple 3D-video, can be displayed even on PDA's.

Related Topics:
Voxels - PDA

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Aspect ratio

Aspect ratio describes the squareness of video screens and video picture elements. The screen aspect ratio of a traditional television screen is 4:3, or 1.33:1. High definition television uses an aspect of 16:9, or about 1.78:1. The aspect ratio of a full 35 mm film frame with soundtrack (also known as "Academy standard") is around 1.37:1.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Pixels on computer monitors are usually square, but pixels used in digital video have non-square aspect ratios, such those used in the PAL and NTSC variants of the CCIR 601 digital video standard, and the corresponding anamorphic widescreen formats.

Related Topics:
Digital video - CCIR 601

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Color space and Bits per pixel

Color model name, describes video color representation. YIQ is used in NTSC television. It corresponds closely to the YUV scheme used in PAL television and the YDbDr scheme used by SECAM television.

Related Topics:
YIQ - YUV - YDbDr

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The number of distinct colours that can be represented by a pixel depends on the number of bits per pixel (bpp). Very common way to reduce number of bits per pixel in digital video is chroma subsampling (for example , , ).

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Stereoscopic

Video with 2 channels - right and left for right and left eye. See articles Stereoscopy and 3-D_film.

Related Topics:
Stereoscopy - 3-D_film

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Video quality

Quality of video can be measured with formal metrics like PSNR or with experts Mean Opinion Score (MOS). Many of MOS methods are described in ITU-T recommendation BT.500.

Related Topics:
Quality of video - PSNR - Mean Opinion Score (MOS) - ITU-T

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Video compression method (for digital only)

Compression method (standard) used for video. Video data contains spatial and temporal redundancy. Similarities can thus be encoded by merely registering differences within a frame (spatial redundancy, named intraframe compression and very close to image compression) and/or between frames (temporal redundancy, named interframe compression use motion compensation and other techniques). Most common standards are MPEG-2 - used for DVD and Satellite television and MPEG-4 - used for home video.

Related Topics:
Compression method - Redundancy - Image compression - Motion compensation - MPEG-2 - DVD - Satellite television - MPEG-4

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Bitrate (for digital only)

Bitrate is a measure of video stream 'speed'. It is quantified using the bit per second (bit/s) unit. Bigger bitrate allows better video quality. For example: 1 Mbit/s ? VHS quality, 5 Mbit/s ? DVD quality 10 Mbit/s ? HDTV quality. Several types of bitrate strategies can be used. To maximize visual video quality variable bitrate (VBR) is used. On fast motion scenes it use more bits, on slow motion - less, we can see constant quality. For video streaming with limited channels (e.g. videoconferencing) constant bitrate (CBR) is used.

Related Topics:
Bitrate - Video quality - Variable bitrate (VBR) - Constant bitrate (CBR)

~ ~ ~ ~ ~ ~ ~ ~ ~ ~