3G SDI
Serial digital interface (SDI) is a serial link standardized by ITU-R BT.656 and the Society of Motion Picture and Television Engineers (SMPTE) that transmits uncompressed digital video over 75-ohm coaxial cable within studios and is seen on most professional video infrastructure equipment. The first revision of the standard, SMPTE 259M, was defined to carry digital representation of analog video such as NTSC and PAL over a serial interface and is more popularly known as standard-definition (SD) SDI. The data rate required to transmit SD SDI is 270 Mbps. With the advent of high-definition (HD) video standards such as 1080i and 720p, the interface was scaled to handle higher data rates of 1.485 Gbps. The 1.485-Gbps serial interface is commonly called the HD SDI interface and is defined by SMPTE 292M and uses the same 75-ohm coaxial cable. Studios and other video production facilities have invested heavily on the hardware infrastructure for coaxial cable and have a vested interest in extending the life of their infrastructure. Fortunately, SMPTE recently ratified a new standard called SMPTE 424M that doubles the SDI data rates to 2.97 Gbps using the same 75-ohm coaxial cable. This new standard, also called 3-Gbps (3G) SDI, enables higher resolution of picture quality required for 1080p and digital cinema.
Altera Solutions for SDI
To enable fast development and deployment of highly flexible next-generation switchers, cameras, servers, and other studio equipment supporting 1080p, Altera provides a fully characterized SDI MegaCore function which can implement triple-rate SDI (SD SDI, HD SDI, and 3G SDI) on the same transceiver pin. It is extremely critical for SDI interfaces to function across process, voltage, and temperature variations. Altera’s SDI characterization of Stratix II GX devices cover all corners of process, voltage, and temperature. Be cautious of products that have not been characterized over all process corners. Please contact your local Altera® representative for more information on characterization. The core has auto detect and auto switch features to switch between SD, HD, and 3G-SDI depending on the type of video data received. Therefore, the core can capture and/or transmit SD video, 720p HD, 1080i HD, or 1080p HD. The triple-rate SDI MegaCore function includes all receive and transmit building blocks for the three key data rates of 270 Mbps, 1.485 Gbps, and 2.970 Gbps (see Figure 1). The receive block has the cyclical redundancy check (CRC) decoder, the line-number extraction, video framing and timing extraction, and the format detector. The transmit block is composed of the CRC encoder and line-number insertion. The legacy SD SDI scrambler block is used for the transmitting side and alignment with descrambling for the receiving side. Altera also offers an audio/video (A/V) development kit based on the Stratix GX II FPGA family, which directly supports 1080p SDI interfacing.
Figure 1. Altera’s Triple Rate SDI Solution Block Diagram
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Table 1 summarizes Altera® SDI solutions for different Altera device families.
| Table 1. Device Support Overview for SDI interface |
| Feature |
Stratix II GX |
Stratix II
Stratix III |
Cyclone® II
Cyclone III |
| SDI Transmit |
 |
|
|
| SDI Receive |
|
|
|
| HD-SDI Transmit |
|
- |
- |
| HD-SDI Receive |
|
- |
- |
| 3G-SDI Transmit |
|
- |
- |
| 3G-SDI Receive |
|
- |
- |
| Triple-Rate SDI Receive |
|
- |
- |
| Triple-Rate SDI Transmit |
|
- |
- |
|
 |
|
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