Video and Image Processing Suite User Guide

ID 683416
Date 2/12/2021

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6.1.3. Interfacing with Serial Digital Interface (SDI)

The succession of SDI standards offers a range of mappings of video samples onto SDI symbols.

The SDI-clocked video interface deals in the SDI symbols, not the video samples. This means that only certain of the SDI mappings are directly compatible with Avalon-ST video requirements. The figure below shows the 8- and 10-bit YCbCr 4:2:2 mappings.

Figure 29. The SDI Sample Mappings Directly Compatible with Avalon-ST Video

You can transport other mappings into the Avalon-ST domain but to rearrange the samples into a compatible format, immediate remapping into the Avalon-ST format is required. The clocked video units do not perform any remapping function.

Figure 30. SMPTE-372 Dual Link Carrying Dual StreamsYCbCr 4:2:2 delivered as SMPTE-372 dual-link format over 2 20 bit buses can be configured either as a single pixel of 4 parallel color planes or 2 pixels of 2 parallel color planes.

If a single pixel configuration is used, then the horizontal resolution would be correct in the Avalon-ST control packet. If the 2 pixel solution were selected, the Avalon-ST control packet would report a width 2x the actual horizontal resolution (since an entire extra line is carried on Link B but it’s pixels would be counted as part of Link As). In both cases, the Avalon-ST control packet would report a vertical resolution ½ the actual resolution since 2 lines have been handled as 1. Any remapping logic has to account for this.

Figure 31. Clocked Video Input Interpretations of SMPTE-372 Dual Link 10-bit RGBA Mapping For 10-bit RGBA carried on a SMPTE-372 dual link remapping is required since 2 cycles of samples are required to assemble complete RGB pixel.

In this case using 1 pixel, 4 color planes in parallel will mean that the control packet reflects the true dimensions of the incoming image. If 2 pixels with 2 color planes is configured, then the control packet will report a horizontal width 2x the actual width.

The 12-bit data mappings also require processing to recombine the relevant SDI symbols into the correct pixel components.

Figure 32. Clocked Video Input Interpretations of SMPTE-372 Dual Link 12-bit RGBA Mapping The12-bit RGB mapping matches the 12-bit YCbCr 4:4:4 mapping if you replace R with Cr, G with Y and B with Cb.
Figure 33. Clocked Video Input Interpretations of SMPTE-372 Dual Link 12-bit YCbCr Mapping The 12 bit 4:2:2 mapping with optional alpha channel also spreads pixel components across multiple SDI symbols requiring remapping to an Avalon-ST Video compliant arrangement.

If you select 2 pixel in parallel configuration, then the control packets from a CVI will report 2x actual width. Going into the CVO, the packets would need to report 2x the actual width.