Source Input Format

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Source Input Format (SIF) defined in MPEG-1, is a video format that was developed to allow the storage and transmission of digital video.

625/50 SIF format (PAL/SECAM) has a resolution of (360 or) 352 x 288 active pixels and a refresh rate of 25 frames per second.
525/59.94 SIF Format (NTSC) has a resolution of (360 or) 352 x 240 active pixels and a refresh rate of 29.97 frames per second.

When compared to the CCIR_601 specifications, which defines the appropriate parameters for digital encoding of TV signals, SIF can be seen as being reduced by half in all of height, width, frame-rate, and chrominance. SIF video is known as a constrained parameters bitstream. [1]

The computer industry has defined square-pixel SIF to be 320 x 240 (QVGA) or 384 x 288 active pixels with a refresh rate of whatever the computer is capable of supporting.