DeepStream Development Skill

This skill requires access to all of the reference documents listed in the references/ directory below. Ensure they are available before executing the workflow.

When this skill is active, ALWAYS read the relevant reference documents before generating code. Do NOT rely on memory - the reference documents contain critical details about exact property names, correct API usage, and common pitfalls.

SDK and Architecture Quick Reference

DeepStream SDK Version Requirements

• GStreamer: 1.24.2
• NVIDIA Driver: 590+
• CUDA: 13.1
• TensorRT: 10.14.1.48
• Platforms: Ubuntu 24.04 (x86_64 and ARM64/Jetson)

Typical Pipeline Flow

Source → Stream Muxer → Inference → [Tracker] → OSD → Renderer

Components in [brackets] are optional -- only add them when the user explicitly requests them.

Memory Model

DeepStream uses NVIDIA Video Memory Manager (NVMM) for zero-copy GPU buffer transfers. Caps strings use memory:NVMM to indicate GPU memory (e.g., video/x-raw(memory:NVMM), format=NV12).

Critical Rules

1. Only Add Requested Components: Do NOT add pipeline elements the user did not ask for.

   • Tracker (nvtracker): Only add when the user explicitly requests tracking or object IDs across frames
   • Secondary GIEs: Only add when the user requests classification or attribute extraction
   • Analytics (nvdsanalytics): Only add when the user requests line crossing, ROI counting, etc.
   • Message broker (nvmsgbroker/nvmsgconv): Only add when the user requests Kafka/cloud messaging
   • When in doubt, build the minimal working pipeline and let the user ask for additions

2. Default to nvurisrcbin for Sources: When the user says "camera", "stream", "video", or provides a file path:

   • Always use nvurisrcbin -- it handles RTSP, HTTP, and local files (file://) transparently
   • Only use filesrc + qtdemux + parser when the user explicitly needs raw file source control
   • For RTSP/live sources, also set live-source=1 on nvstreammux and sync=0 on the sink
   • Convert local paths to URI: "file://" + os.path.abspath(path)

3. Metadata Iteration: Use .frame_items and .object_items (returns iterators, NOT lists)

   • NEVER use len() on these - iterate to count
   • Iterator can only be consumed once

4. Request Pad Syntax: Use "sink_%u" template, NEVER literal pad names

   pipeline.link(("decoder", "mux"), ("", "sink_%u"))  # CORRECT
   # pipeline.link(("decoder", "mux"), ("", "sink_0"))  # WRONG - will fail
   

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5. Platform Detection for Sinks:

   import platform
   sink_type = "nv3dsink" if platform.processor() == "aarch64" else "nveglglessink"
   

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   • For WSL2 Ubuntu 24 Docker, this default selection must be overridden.
   • WSL2 + Ubuntu 24 Docker: If /proc/version contains microsoft or wsl and /etc/os-release has VERSION_ID="24.04", the generated app must never create a display branch or display sink (nveglglessink, nv3dsink, etc.), even if the prompt asks for display. Do not rely on a --no-display flag for this case. Generate encoded MP4 output only (nvv4l2h264enc -> h264parse -> mp4mux/qtmux -> filesink) and make the default run path write the annotated video file. In the generated README.md, explicitly explain that WSL2 Ubuntu 24 Docker is MP4-output-only because display sinks are disabled by a known issue. If the user explicitly requested display, add an inline code comment and README note explaining: Display requested but disabled due to WSL2 Ubuntu 24 Docker limitation — MP4 output generated instead.
   • Non-WSL targets: Do not add WSL-specific behavior or WSL limitation text to generated apps or READMEs. Use the normal platform display sink selection above.

6. Buffer Cloning: Always clone buffers for async processing

   tensor = buffer.extract(0).clone()  # CRITICAL
   

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7. Queue Types:

   • queue.Queue → Use with threading.Thread
   • multiprocessing.Queue → Use with multiprocessing.Process
   • Using wrong type causes silent data loss!

8. nvinfer Config Format:

   • YAML: Use property: section (NOT model:), key: value with space after colon
   • INI: Use [property] section, key=value with equals sign
   • Section MUST be named property

9. nvmsgbroker is a SINK: Cannot have downstream elements - use tee to split pipeline

10. ALL Sinks Need async=0 for Tee Splits or Dynamic Sources: CRITICAL for state transitions

    # When using tee splits OR dynamic sources, ALL sinks MUST have async=0
    pipeline.add("nveglglessink", "sink", {
        "sync": 0, "qos": 0,
        "async": 0  # CRITICAL - prevents state transition deadlock
    })
    

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    Symptom if missing: Pipeline stays in PAUSED state, no video displays.

11. Built-in Probe Attachment: measure_fps_probe can only be attached to processing elements (e.g., nvinfer, nvosdbin), NOT to sink elements. Attaching to a sink raises RuntimeError: Probe failure.

12. Dynamic ONNX Models Require infer-dims: When the ONNX model has dynamic input shapes (e.g., exported with dynamic=True in Ultralytics YOLO, or with dynamic batch/height/width axes), you MUST add infer-dims=C;H;W to the nvinfer config. Without it, TensorRT sees -1 for dynamic dimensions and fails with setDimensions: Error Code 3. Common values:

    • YOLO models (640 input): infer-dims=3;640;640
    • Models with 416 input: infer-dims=3;416;416
    • Models with 1280 input: infer-dims=3;1280;1280

13. Ultralytics YOLO Output Format Depends on Model Generation — newer models (v10+/v26+) output post-NMS results; older models (v8/v11) output raw pre-NMS tensors. The custom parser and cluster-mode must match the actual output:

How to identify at runtime: log inferDims.d[0] and inferDims.d[1] inside the custom parser.

• d={84, 8400} → pre-NMS (v8/v11 style)
• d={300, 6} → post-NMS (v10/v26+ style)

Symptom of mismatch: If cluster-mode: 2 is used with a post-NMS [N, 6] output, bounding boxes appear shifted by 45° or 135° from the actual objects (DeepStream's NMS incorrectly re-processes already-final coordinates). If you see tilted or rotated boxes, also check the OBB / rotation_angle note in references/nvinfer_config.md: for non-OBB models, value-initialize NvDsInferObjectDetectionInfo with obj{} and keep rotation_angle = 0; plain NvDsInferObjectDetectionInfo obj; leaves fields uninitialized.

14. Virtual Environment Must Include pyservicemaker: pyservicemaker is installed system-wide but is NOT accessible from a standard Python virtual environment. When a task requires a venv (e.g., for model download/conversion pip dependencies), always install pyservicemaker and pyyaml inside the venv; do not rewrite pyservicemaker pipeline code into non-pyservicemaker code to work around a missing import. The venv setup in generated code and README must always include:

    python3 -m venv venv
    source venv/bin/activate
    pip install /opt/nvidia/deepstream/deepstream/service-maker/python/pyservicemaker*.whl pyyaml
    pip install -r requirements.txt  # other dependencies
    

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    Symptom if missing: ModuleNotFoundError: No module named 'pyservicemaker' when running the app inside the venv.

Key Paths

• Models: /opt/nvidia/deepstream/deepstream/samples/models/
• Primary Detector: /opt/nvidia/deepstream/deepstream/samples/models/Primary_Detector/resnet18_trafficcamnet_pruned.onnx
• Tracker lib: /opt/nvidia/deepstream/deepstream/lib/libnvds_nvmultiobjecttracker.so
• Kafka lib: /opt/nvidia/deepstream/deepstream/lib/libnvds_kafka_proto.so
• Sample configs: /opt/nvidia/deepstream/deepstream/samples/configs/deepstream-app/

Reference Documents

IMPORTANT: Always read these documents for complete details. Do NOT generate code from memory.

Quick Error Reference