Unexpected variable latency in interlaced mode

Hi!

I noticed that the transmission latency is not predictable when transmitting a 1080i50 stream (also reproducible with 1080i59.94) using the TxSt20PipelineSample.

I sometimes observe a latency of approximately 542 lines early (~19 ms) :

And other times I observe a latency of approximately 21 lines late (~0.736 ms) :

The latency is measured using a Telestream PRISM.

This issue does not occur in progressive mode.

I can reproduce the issue using the following command:

sudo ./build/app/TxSt20PipelineSample  -p_port XXXXXXXXXX -p_sip AA.BB.CC.DD  -udp_port 1234 -p_tx_ip WW.XX.YY.ZZ -payload_type 96 -interlaced -fps 50  -ptp

The issue is also reproducible with RxTxApp using the following JSON configuration:

{
    "interfaces": [
        {
            "name": "XXXXXXXXXX",
            "ip": "AA.BB.CC.DD"
        }
    ],
    "tx_sessions": [
        {
            "dip": [
		"WW.XX.YY.ZZ"
            ],
            "interface": [
                0
            ],
            "st20p": [
                {
                    "replicas": 1,
                    "start_port": 1234,
                    "payload_type": 96,
                    "width": 1920,
                    "height": 1080,
		    "interlaced": true,
                    "fps": "p50",
                    "device": "AUTO",
                    "input_format": "YUV422PLANAR10LE",
                    "transport_format": "YUV_422_10bit",
                    "st20p_url": "testyuv"
                }
            ]
        }
    ]
}

RxTxApp output log:
RxTxApp_log.txt

MTL version : main branch 982e2ea5520d5ad2a10790a462907202570b8a43
OS : Ubuntu 22.04.5 LTS

Status report:
system_info.txt
kernel_log.txt

Thank you in advance for your feedback.