2.209.203.92 at 16:59, 16 September 2024

2024-09-16T16:59:01Z

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{{Short description|File format}}
{{Refimprove|date=November 2006}}

'''Source Input Format''' ('''SIF''') defined in [[MPEG-1]], is a video format that was developed to allow the storage and transmission of [[digital video]].<ref>{{cite web |title=Digital S Term Dictionary |url=http://pro.jvc.com/pro/d9/DIGITALS/thedictionary/terms/s017.html |access-date=2023-04-18 |website=JVC Professional}}</ref><ref name=":0">{{cite book |url=https://www.itu.int/wftp3/av-arch/avc-site/1990-1996/Contributions/AVC-0033.pdf |title=Setup of CCIR 601 multi-purpose coding system |publisher=PTT Research |year=1991}}</ref>

* [[625 lines|625/50]] SIF format ([[PAL]]/[[SECAM]]) has a resolution of '''{{resx|352|288}}''' active pixels (half of PAL {{resx|704|576}}) [or {{resx|360|288}} active pixels (half of PAL {{resx|720|576}})] and a [[refresh rate]] of 25 frames per second.<ref name=":0" />
* [[525 lines|525/59.94]] SIF Format ([[NTSC]]) has a resolution of '''{{resx|352|240}}''' active pixels (half of NTSC {{resx|704|480}}) [or {{resx|360|240}} active pixels (half of NTSC {{resx|720|480}})] and a refresh rate of 29.97 frames per second.<ref name=":0" />

When compared to the [[Rec. 601|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]].<ref>{{cite web |date=2009-04-12 |title=MPEG-1 VIDEO |url=http://bmrc.berkeley.edu/frame/research/mpeg/faq/mpeg1.html |access-date=2023-04-18 |website=Berkeley Multimedia Research Center |archive-url=https://web.archive.org/web/20090412155022/http://bmrc.berkeley.edu/frame/research/mpeg/faq/mpeg1.html |archive-date=2009-04-12}}</ref>

On [[Pixel aspect ratio|square-pixel]] displays (e.g., computer screens and many modern televisions) SIF images should be rescaled so that the picture covers a 4:3 area, in order to avoid a "stretched" look. So the computer industry has defined "square-pixel SIF" to be 320 x 240 active pixels ([[Graphics display resolution#QVGA (320×240)|QVGA]]) or 384 x 288 active pixels, with a refresh rate of whatever the computer is capable of supporting. To reach that the SIF content need to be "expanded" horizontally by 12:11 for PAL ([[pixel aspect ratio#Pixel aspect ratios of common video formats|PAR]] = [[Display aspect ratio|DAR]] : [[Aspect ratio (image)#storage aspect ratio|SAR]] = {{sfrac|4|3}} : {{sfrac|352|288}} = {{sfrac|12|11}}) and "reduced" horizontally by 10:11 for NTSC (PAR = DAR : SAR = {{sfrac|4|3}} : {{sfrac|352|240}} = {{sfrac|10|11}}).

== See also ==
* [[Common Intermediate Format|Common Intermediate Format (CIF)]]

== References ==
{{reflist}}
{{TV resolution}}

[[Category:Graphics standards]]
[[Category:MPEG]]

{{tv-tech-stub}}

Source Input Format - Revision history

2.209.203.92 at 16:59, 16 September 2024