ST30P_TX_FLAG_DROP_WHEN_LATE does not work in st30p Tx

[DianaEs2]

The stat_epoch_drop is never reported for late audio frames. The code reporting the statistics is unreachable.

Tested this commit 888e1c6 ("Add: St40p support in RxTxApp", 2025-12-11)

The config file was this local_tx_1a.json

Simulate 1-second sleep in tx_st30p_app commit-9e6a4db.patch

Here is the result. stat_epoch_mismatch is reported instead of stat_epoch_drop

app_tx_st30p_frame_thread(0), get frame time out
MTL: 2025-12-12 08:48:25, * * M T D E V S T A T E * *
MTL: 2025-12-12 08:48:25, DEV(0): Avr rate, tx: 2.735179 Mb/s, rx: 0.000000 Mb/s, pkts, tx: 9997, rx: 0
MTL: 2025-12-12 08:48:25, DEV(1): Avr rate, tx: 2.735453 Mb/s, rx: 0.000000 Mb/s, pkts, tx: 9998, rx: 0
MTL: 2025-12-12 08:48:25, SCH(0:sch_0): tasklets 2, lcore 1(t_pid: 2104434), avg loop 157 ns
MTL: 2025-12-12 08:48:25, CNI(0): eth_rx_rate 0.000000 Mb/s, eth_rx_cnt 0
MTL: 2025-12-12 08:48:25, CNI(1): eth_rx_rate 0.000000 Mb/s, eth_rx_cnt 0
MTL: 2025-12-12 08:48:25, PTP(0): time 1765547342648058576, 2025-12-12 08:49:02
MTL: 2025-12-12 08:48:25, TX_AUDIO_SESSION(0,0:app_tx_st30p_0): fps 1000.086325 frames 10001, pkts 10001:10001 inflight 0:0
MTL: 2025-12-12 08:48:25, TX_AUDIO_SESSION(0,0): epoch mismatch 989
MTL: 2025-12-12 08:48:25, TX_AUDIO_SESSION(0,0): error user timestamp 988
MTL: 2025-12-12 08:48:25, TX_AUDIO_MGR(0), pkts burst 20002
MTL: 2025-12-12 08:48:25, TX_st30p(0,app_tx_st30p_0), framebuffer queue: R:3
MTL: 2025-12-12 08:48:25, TX_st30p(0), frame get try 10002 succ 10001, put 10001, drop 0
MTL: 2025-12-12 08:48:25, * * E N D S T A T E * *

[DianaEs2]

The previous test was to introduce a late audio frame by adding 1 sec sleep. And observe that no drop frame happened.
MTL: 2025-12-12 08:48:25, TX_st30p(0), frame get try 10002 succ 10001, put 10001, drop 0

This test is to introduce a 1 sec gap in timestamp and observe that every second frame is dropped and the audio cannot recover.
MTL: 2026-02-25 10:03:14, TX_st30p(0), frame get try 1000 succ 1000, put 1000, drop 500

Here is the patch to repo the timestamp gap commit-7da0ba0.patch and the resulting log mtl_out.log. Tested with this config local_tx_1a.json.

[DianaEs2]

It seems the code actually does the opposite - it drops early frames rather than late ones.
This patch works for me commit-402340e.patch

[DianaEs2]

The drop frame functionality was refactored. Tested at this commit, and it works fine.
204368f ("Fix: make sure the app is notified on drop frames", 2026-03-19)