Source Input Format
Source Input Format defined in MPEG-1
MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting possible.Today, MPEG-1 has become...

, is a video format that was developed to allow the storage and transmission of digital video.
  • 625/50 SIF format (PAL
    PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...

    SECAM, also written SÉCAM , is an analog color television system first used in France....

    ) has a resolution of (360 or) 352 x 288 active pixels and a refresh rate
    Refresh rate
    The refresh rate is the number of times in a second that a display hardware draws the data...

     of 25 frames per second.
  • 525/59.94 SIF Format (NTSC
    NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...

    ) 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
CCIR 601
ITU-R Recommendation BT.601, more commonly known by the abbreviations Rec. 601 or BT.601 is a standard published in 1982 by International Telecommunication Union - Radiocommunications sector for encoding interlaced analog video signals in digital video form...

 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.

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.
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