SDI II Intel® FPGA IP User Guide

ID 683133
Date 10/08/2021

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5.3.17. Detect Format

The detect format submodule monitors the line and frame timing of an incoming SDI stream. It generates various flags to indicate whether the receive stream is locked, and reports matching known video formats as rx_format.

A word counter monitors the EAV and SAV positions in the incoming video. The word counter increments on each valid word and stores the count value when an EAV or SAV is seen. If the count values are the same as a predefined value, the core determines the incoming video to be TRS locked. The predefined value is set to 6, therefore after six consecutive lines of the same EAV and SAV timing, the rx_trs_locked signal is active.

A line counter increments at the start of each video line. When the core finds the first active line of a field or frame, the line counter starts incrementing until the last active line of the same field or frame.

To determine the video format, a comparison logic compares the word and line count values in the video stream against the known values predefined for various video formats. The logic searches sequentially from one known value to another.
  • If the logic finds a match, the core is determined to be frame locked and the rx_frame_locked signal is active. The core reports the matched known value as rx_format.
  • If the logic does not find any match and the count is consistent over two video frames, the rx_frame_locked signal remains active but the rx_format stays asserted.
In 6G / 12G-SDI, where multiple sub-images form multiple 20-bit Y/C streams, this submodules are present in every 20-bits processing block as illustrated in to detect the incoming transport format of each stream. The rx_format would then report the detected transport format for each of these streams respectively if there is a match.