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rx_st40p: UDW parity check fails for multi-packet ANC frame #1506

@DianaEs2

Description

@DianaEs2

Test setup: MTL version was taken at this commit dcb43aa ("Fix: use PRIu64 format for uint64_t in rv_simulate_pkt_loss debug log (#1492)", 2026-04-10)
tx_st40p session transmitted ancillary without ST40P_TX_FLAG_SPLIT_ANC_BY_PKT.
It produced a compliant stream non_split_anc.zip

Image Image

Actual result: rx_st40p session which was running on the same machine received broken stream. The following error was logged
04-08 18:13:43.591 INFO Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: PTP(0): time 1775672060591679098, 2026-04-08 18:14:20
04-08 18:13:43.591 INFO Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: RX_ANC_SESSION(0:rx_st40p_1): fps 59.899545 frames 599 pkts 599 (redundant 599)
04-08 18:13:43.591 INFO Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: RX_ANC_SESSION(0): interlace first field 598 second field 600
04-08 18:13:43.591 INFO Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: RX_st40p(0,rx_st40p_1), p(7:free) c(7:free)
04-08 18:13:43.591 INFO Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: RX_st40p(0), frame get try 599 succ 599, put 599
...
04-08 18:13:15.434 WARNING Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: Warn: rx_st40p_rtp_ready(0), UDW parity failure packet 2 word 1
04-08 18:13:15.467 WARNING Intel2110Config_GLOBAL [Intel2110_Logging_BG-1]: /: MTL: Warn: rx_st40p_rtp_ready(0), UDW parity failure packet 2 word 1
...
_

Expected result: Rx ancillary pipeline session should be able to receive such stream without error.

Workaround: splitting ancillary frame into multiple RTP packets in tx_st40p helped to parse this stream in rx_st40p correctly. But the original test case was valid and is not supported.

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