What's the difference between SIF and CIF?
This article applies to the following products:
- Cisco TelePresence IP GW 3500 / MSE IPGW blade
- Cisco TelePresence IP VCR 2200 / MSE VCR blade
- Cisco TelePresence ISDN GW 3200 and 3241 / MSE 8310 and 8321 ISDN blades
- Cisco TelePresence MCU 4200 Series
- Cisco TelePresence MCU 4500 Series
- Cisco TelePresence MCU 5300 Series
- Cisco TelePresence MCU MSE Series
- Cisco TelePresence Advanced Media Gateway 3600
- Cisco TelePresence Serial GW 3340 / MSE 8330 blade
CIF and SIF are acronyms that describe video resolutions and have come to video conferencing from the broadcast industry.
CIF stands for Common Interchange Format and represents a resolution of 352 x 288. This is the resolution used by PAL (European) television systems. Related resolutions are QCIF (Quarter CIF) and 4CIF which are 176 x 144 and 704 x 576 respectively.
SIF stands for Standard Interchange Format and represents a resolution of 352 x 240. This is the resolution used by NTSC (North American) television systems. Related resolutions are QSIF (Quarter SIF) and 4SIF which are 176 x 120 and 704 x 480 respectively.
Both CIF and SIF are fullscreen (4:3) resolutions; the resolution 512 x 288 is sometimes referred to as WCIF (Wide CIF) but is more commonly known as w288p.
Some endpoints are available with a choice of PAL or NTSC cameras: a PAL camera operates at 25fps and an NTSC camera at 30fps. Due to the larger frame size of PAL (CIF) over NTSC (SIF), they both generate the same amount of information.
If H.264 level 2.1 is used unmodified, 4SIF will be possible at 15fps and 4CIF at 12.5fps.