visual quality that is comparable to Digital Betacam MPEG IMX is not supported in the XDCAM EX product line. MPEG HD is used in all product lines except for XDCAM SD. This format supports multiple frame sizes, frame rates, scanning types and quality modes. Depending on product line or a particular model, not all modes of this format may be available. MPEG HD422 doubles the chroma horizontal resolution compared to the previous generations of high-definition video XDCAM formats. To accommodate the improved chroma detail, video bitrate has been increased to 50 Mbit/s. This format is used only in XDCAM HD422 products. MPEG SHD422 XDCAM-SHD422 stands for "Super HD" and has been introduced later on to preserve more details. It maintains the 4:2:2 planar chroma sampling as well as the same resolution of MPEG HD422, but it increases the bitrate to 85 Mbit/s. This format has never become widely used and a very limited set of devices support it. Proxy AV is used to record low resolution proxy videos. This format employs MPEG-4 video encoding at 1.5 Mbit/s (CIF resolution) with 64 kbit/s (8 kHz A-law, ISDN-quality) for each audio channel. XDCAM formats 1 720p @ 19 Mbit/s is offered by JVC and is equivalent to HDV 720p XDCAM-SHD422 has a very limited support, therefore it's not included in the table. Recording media Professional Disc (XDCAM and XDCAM HD) The Professional Disc was chosen by Sony as its medium for professional non-linear video acquisition for a number of reasons, outlined in their white-paper Why Sony Adopted Professional Disc. This disc is similar to Blu-ray Disc and holds either 23 GB of data (PFD23, single-layer, rewritable), 50 GB (PFD50, dual-layer, rewritable), 100 GB (PFD100TLA, triple-layer, rewritable) or 128 GB (PFD128QLW, quad-layer, write-once). Essentially, the Professional Disc format was deemed to be a suitable, cost effective and easy step forward. The discs are reliable and robust, suitable for field work (something which has previously been a problem with many disc-based systems). Additionally, the cost of media is comparable to existing professional formats. SxS In 2008, Sony introduced a new recording medium to their XDCAM range SxS Pro (pronounced "S-by-S"). It is a solid-state memory card implemented as an ExpressCard module. The first camera to use this media was the Sony PMW-EX1 professional video camera. In December 2009, Sony introduced the more affordable SxS-1. This unit is designed to have the same performance as