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.
- 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.