What is HD-SDI?

What is HD SDI (Briefly)

HD-SDI is a new technology in CCTV that offers High Definition 720 and 1080P resolution video over standard Coax cabling.
These HD-SDI CCTV products are ideal for upgrading existing analogue CCTV Installations where higher resolution HD images and performance are required.

SDI is the transmitting technology through the 75ohm coaxial cable by serializing the video signal that is not compressed.
The video signal that is transmitting through SDI is a kind of digital signal. Therefore, contrary to the analog signal which is influenced by the deformation of video signal and the distance of transmit, it is possible to transmit the video signal without limitation of distance and deformation of signal through Equalization and Recloking of the video signal at intervals.

What is HD SDI (Details)

HD-SDI stands for High-Definition Serial Digital Interface. It is the common term for a high-definition digital video transmission standard known as SMPTE 292M.

The SMPTE 292M standard is part of a family of Serial Digital Interface standards that use a coaxial cable to transport uncompressed digital video – currently still predominantly used in professional TV studios.

In short, HD-SDI is a standard for transmitting uncompressed broadcast-grade HD video signals over short distances.

More than 400 interface standards are published by the Society of Motion Picture and Television Engineers (SMPTE), an internationally recognized industry organization that develops common standards, practices and guidelines mostly for television and cinema.

HD-SDI Bit Rates

The 292M interface of the HD-SDI standard has a nominal data rate of 1.5 Gbps. To be precise, the standard specifies two exact bit rates:

• 1.485 Gbps
  Supports 60 Hz, 50 Hz, 30 Hz, 25 Hz, 24 Hz and other commonly used frame      rates.
• 1/485/1.001 Gbps
  Allows the standard to support video formats with frame rates of 59.94 Hz,      29.97 Hz and 23.98 Hz, making it upwards compatible with existing NTSC      (analogue video) systems.

HD-SDI Extensions

HD-SDI can be taken to even greater levels with the following emerging interfaces:

• Dual Link HD-SDI (SMPTE 372M)
  A dual-link extension of SMPTE 292M is used for very high-definition      applications. Essentially consisting of a pair of SMPTE 292M links, this      standard is known as SMPTE 372M. It provides a nominal 2.970 Gbps      interface that is used in applications that require greater resolution and      greater fidelity than standard HDTV can provide (e.g. HDTV 1080P or      digital cinema).
• 3G-SDI (SMPTE 424M)
  The 3G (3 Gbps) SDI standard is a very recent interface, defined in the      SMPTE 424M standard. It consists of a single 2.970 Gbps serial link      and is likely to replace the dual link HD-SDI.

What SMPTE is

 

The Society of Motion Picture and Television Engineers – or SMPTE – is an international professional association of engineers working in various motion imaging industries. The society was founded in the US in 1916 as the Society of Motion Picture Engineers, with Television added to the name several decades later.

SMPTE develops all internationally recognized transmission formats and standards, recommended practices and engineering guidelines for television, motion pictures, digital cinema, audio and medical imaging.

Serial Digital Interface (SDI) is a family of SMPTE-published standards that define the digital video interfaces used for broadcast-grade video.

Refer to the chart below for technical specifications of Standard Definition SDI, Enhanced Definition SDI, High Definition SDI, Dual-Link HD-SDI and 3G-SDI.

 SDI Comparison Chart

 

Name	Standard	Bit   rates (data transfer speed)	Sample   video formats
SD-SDI Standard Definition SDI	SMPTE   259M	270 Mpbs (most common) 360 MBps (widescreen) 143 Mbps, 177 Mbps        (NTSC/PAL)	480i,   576i, 625i widescreen270 Mpbs supports 525-line interlaced video at a 59.94   Hz field rate (29.97 Hz frame rate) and 625-line, 50 Hz interlaced video.   Highly compatible with NTSC and PAL-B/G/D/K/I systems.
ED-SDI Enhanced Definition SDI	SMPTE   344M	540 Mbps Dual-link 270 Mpbs	480p,   576p, 525p, 625p
HD-SDI High Definition SDI	SMPTE   292M	1.485 Gbps 1.485/1.001 Gbps        (supporting frame rates of 59.94 Hz, 29.97 Hz and 23.98 Hz to be        compatible with NTSC systems) Commonly   collectively referred to as nominal bit rate of 1.5 Gbps	1080/60i,   1080/59.94i, 1080/50i, 1080/30p, 1080/29.97p, 1080/25p, 1080/24p,   1080/23.98p, 720/60p, 720/59.94p, 720/50p, 1080psf
DL   HD-SDIDual-Link High   Definition SDI (double cables)	SMPTE   372M	2.970 Gbps 2.970/1.001 Gbps	1080/60p,   1080/59.94p, 1080/50p
3G-SDI 3 Gbps SDI This single cable link will replace dual-link HD-SDI in future	SMPTE   424M	2.970 Gbps 2.970/1.001 Gbps Commonly   collectively referred to as nominal bit rate of 3 Gbps

How 720p and 1080p Are Similar and Different

Contrary to what some may believe, 720p and 1080p are actually both high definition video display formats. In addition, the other characteristic 1080p and 720p share in common is that they are progressive display formats (that is where the “p” comes from). However, this is where the similarity between 720p and 1080p ends.

720p is 1,280 pixels displayed across the screen horizontally and 720 pixels down the screen vertically. This arrangement yields 720 horizontal lines on the screen, which are, in turn, displayed progressively, or each line displayed following another.

1080p represents 1,920 pixels displayed across the screen horizontally and 1,080 pixels down the screen vertically. This arrangement yields 1,080 horizontal lines on the screen, which are, in turn, displayed progressively, or each line of pixels displayed following another. In other words, all lines are displayed progressively, providing the most detailed high definition video image that is currently available to consumers.

The main difference between 720p and 1080p lies in the number of pixels that make up a 720p image and 1080p image. For 720p the number of pixels that make up the image is about 1 million (equivalent to 1 megapixel in a digital still camera) and about 2 million pixels for 1080p. This means that a 1080p image has the potential to display a lot more detail than a 720p image.

However, how does this all translate to what you actually see on a TV screen? Shouldn’t it be easy to see the difference between a 720p and 1080p TV? Not necessarily.

Besides pixel density of 1080p vs 720p, there are also the factors of screen size and seating distance from the screen to take into consideration.