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video formatThe structure of an electronic movie. The digital formats have many more options than the older analog formats.
Digital Video Formats
Following are the encoding variables in a digital video format. See HD formats, SD formats, codec examples and DTV.
Compression (DCT, MPEG, etc.)
The compression algorithm reduces the size of the video content by eliminating pixels, saving bandwidth and storage space. See data compression.
Interframe vs. Intraframe
Interframe coding saves space by creating partial frames, which has implications when editing later on. See interframe coding.
Chroma Subsampling and Bit Rate
Chroma subsampling saves space by compressing the color components, while the bit rate determines how much data can be encoded in each frame. See chroma subsampling and bit rate.
Resolution, Frame Rate and Progressive/Interlace
The horizontal and vertical resolution determines the aspect ratio of the frame and whether it is standard definition (SD) or high definition (HD), while the number of frames per second (frame rate) has impact on scenes with high-speed action. In progressive scan, there is twice as much information per frame as there is in the interlace method. See screen resolution and progressive scan.
Summary of Digital Video Format Variables
1 - compression (DCT, MPEG, etc.)
2 - interframe vs. intraframe
3 - chroma subsampling
4 - bit rate
5 - horizontal/vertical resolution
6 - frame rate
7 - progressive scan vs. interlace
Analog Video Formats
Following are the encoding variables in the analog NTSC, PAL and SECAM video formats. PAL and SECAM are still broadcast in some countries, and all of these formats still exist on VHS tapes. Modern digital TVs may provide one or more types of analog inputs to accommodate them. DVDs were on the market long before digital TVs were commonplace, and although encoded in the MPEG-2 digital format, DVDs conform to NTSC and PAL/SECAM resolutions and frame rates.
Resolution, Frame Rate and Interlace
NTSC, PAL and SECAM are interlaced standard definition (SD) formats. NTSC has 480 lines of resolution at 30 frames per second (fps), and PAL and SECAM have 576 lines at 25 fps. See NTSC, PAL, SECAM and interlace.
Component, S-Video and Composite
NTSC and PAL are mastered in the YUV color space, which requires three "component video" cables to carry the video signals (SECAM uses a variation of YUV). As the content is transferred to VHS tapes and other lower-quality destinations, colors are combined to save bandwidth, and only one cable is used. See YUV, component video, S-video and composite video.
Summary of Analog Video Format Variables
1 - horizontal/vertical resolution
2 - frame rate
3 - progressive scan vs. interlace
4 - component, S-video and composite