How does serial digital interface (SDI) work?
Digital video and audio are transmitted using serial digital interface (SDI) over coaxial or fiber optic cables. For the most recent standard released in 2015, speeds range from 270 megabits per second (Mbps) up to 12 gigabits per second (Gbps).
SDI uses 8 or 10 bit data words. In SdI codice signals, the source (transmitter) and destination (receiver) are uncompressed and self-synchronised. The Hamming code can be used to recover the data lost by noise or interference. In SDI, the video signal can be accompanied by up to four independent digital audio signals.
SDI’s history
This professional video standard was created in 1989 by the Society of Motion Picture and Television Engineers (SMPTE).
There have been six SDI standards released since then, and one is in development. The order in which they were released is as follows:
- This 1989 SMPTE standard enables video and embedded audio to be transmitted and received at bit rates between 177 Mbps and 270 Mbps; it is primarily used for 480i and 576i video formats.
- HD-SDI, introduced in 1998, is a SMPTE 292M standard for transmitting and receiving video and embedded audio at a rate of 1.5 Gbps; it is primarily used to transmit and receive 720p and 1080i videos.
- ED-SDI is an SMPTE 344M standard for transmitting and receiving video and audio at a bit rate of 540 Mbps, and it is primarily used for 480p and 576p video. It was introduced in 2000.
- It uses dual 1.5 Gbps links, resulting in a combined 3 Gbps bit rate, and is primarily used for broadcasting 1080p video. At its release in 2002, Dual Link HD-SDI was an SMPTE 372M standard.
- 3G-SDI. Introduced in 2006, 3G-SDI uses a bit rate of 3 Gbps for transmitting and receiving video and audio; it is usually used to transmit and receive 1080p video footage.
- It transmits and receives video and embedded audio at a bit rate of 6 Gbps; it is primarily used for 1080p video at 60 frames per second and 2160p video at 30 frames per second. 6G-SDI was published in 2015 in SMPTE ST 2081.
- A 2016 SMPTE ST 2082 standard, 12G-SDI transmits and receives video and embedded audio at a bit rate of 12 Gbps; it is primarily used for 2160p video formats at 60 frames per second.
How does HDMI differ from SDI?
The high-definition multimedia interface (HDMI) and the serial digital interface (SDI) can both transmit uncompressed video and digital audio, but they have significant differences in terms of their prices and implementation requirements. Consumer-grade equipment uses HDMI to connect Blu-ray players, streaming devices, and video game consoles to televisions. Its resolution can reach 10K at 120 Hz.
Typically, HDMI cables cannot extend beyond 50 feet without the assistance of an intermediary device. The downside is that it is much less expensive than SDI. The most common HDMI connector type is the 19-pin connector.
Broadcast picture and sound engineers use SDI more often in professional environments. SDI equipment is much more expensive than HDMI equipment, but it does allow for greater transmission that can reach 100 feet over coax cable and 1,000 feet over optical fibre. HDMI can technically transmit higher-fidelity video signals, but SDI is still preferred by professionals because SDI is natively supported by the video equipment interfaces. The BNC connector is used for SDI over coax.
