GStreamer DeepStream Pipeline - Failed queue_pre → streammux linking despite GST_PAD_LINK_OK

I’m building a DeepStream inference pipeline for face detection using RTSP sources, but I’m encountering an issue with linking the queue to `nvstreammux`. The pipeline builds successfully, but the dynamic linking to `streammux` appears to fail even though the return code shows `GST_PAD_LINK_OK`.

Code snippet:

```python

# Link queue → streammux

mux_sinkpad = streammux.get_request_pad(“sink_0”)

queue_srcpad = queue_pre.get_static_pad(“src”)

link_result = queue_srcpad.link(mux_sinkpad)

print(f"Pad link result: {link_result}")

if link_result != Gst.PadLinkReturn.OK:

self.log("ERROR", "Failed queue_pre → streammux linking")

return False

```

Expected behavior:

The pipeline should successfully link all elements including the queue to the streammux, allowing the RTSP stream to flow through the inference pipeline.

Actual behavior:

- Pipeline builds without errors

- Pad link returns `GST_PAD_LINK_OK`

- However, the streammux linking appears to fail silently

- No video frames reach the inference element

Environment:

- NVIDIA Jetson platform

- DeepStream SDK

- GStreamer with Python bindings

- RTSP source input

**What I’ve tried:**

- Verified all elements are properly added to the pipeline

- Confirmed queue properties (max-size-buffers, leaky settings)

- Checked that streammux properties are correctly set (batch-size, dimensions)

Question:

Is there a specific approach required for linking to `nvstreammux` request pads, or are there additional properties I need to set on the queue or streammux elements for RTSP sources?