7. ICMP
7.6 ICM P SDI specifications
3G-SDI
Serial Digital Interface (SDI) is a s erial link standardized by ITU-R BT.656 and th e Society of Motion Picture and Tele-
vision Engineer s (SM PT E). SDI transmits uncomp ressed digital video over 75-ohm coaxial cable within studios, and
is seen on most professional video infrastructure equipment. The first revision of t he standard, SMP TE 25 9M, was
defined to carry digital representation of analog v ideo such as NTSC and PA L over a serial interface and is m ore pop-
ularly known as standard-definition (S D) SDI. T he data rate required to transmit SD SDI is 270 Mbps. W it
h the advent
of high-definition (HD) v ideo standards such as 1080i and 7 20p, the interface was scaled t o handle higher data rates
of 1.485 Gbps . T he 1.485-Gbps serial interface is commonly called the HD SDI interface and is defined by SMPTE
292M, using the same 75-ohm c oaxial cable. S tud ios an d other video production facilities have
invested heavily on
the hardware infrastructure for coaxial cable and have a ves ted interest in extending the life of their infrastructure. For-
tunately, SMPTE recently ratifi ed a new standard called SMPTE 424M that doubles the SDI data rates to 2.97 Gbps
using the same 75-ohm coaxial cable. This n e w standard, also called 3-Gbps (3G)-SDI, ena
bles higher resolution of
picture quality required for 1080p and digital cinema.
SDI terminology
Standard H D- SDI signal
Single Link
1.5Gb/s HD 4:2:2
Standard HD-SDI allows for a single 4:2:2 im age to be carried on one cable at 1.485 Gb/s. The image uses the Y Cb Cr colorspace
and uses a bit depth of 1 0 bit per color component.
Due to the data rate limitations only 23.976, 24, 25, 29.970 and 30 fps streams are achievable.
Dual-Link HD-SDI signal
Dual Link
1.5Gb/s
1.5Gb/s
1080p 50/60
1
or
1080p 4:4:4
Dual-Link HD-SDI is m ainly two standard HD-SD I signals carrying a single image stream split between the two cables. The main
advantage is that color s ubsam pling is no longer required, and the image can be transmitted in 4:4:4 quality, wh ich then also allows
the RGB (or XYZ ) color space to be us ed.
The main link will contain a standard HD-S DI s ignal, the second (enhancement) link contains the miss ing Cb and Cr samples.
Depending on the implementation the en hancem ent link could also contain extra information to increase the bit depth.
3G HD-SD I signal
3G
3Gb/s
1080p 50/60 (Level A)
or
1080p 4:4:4 (Level B)
3G HD-SDI uses a higher data rate (2.97 Gb /s). This allows a single cable interface to a chieve the same capabilities of a Dual-Link
HD-SDI implementation.
In direct mapping (level A) this is used to achieve higher frame rates. (50, 59.940 and 60 fps streams are supported).
1. Not supported in Alchemy
62 R5906847 DP2K SLP SERIES 02/06/2017
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