Gst-nvinfer ============ The Gst-nvinfer plugin does inferencing on input data using NVIDIA® TensorRT™. The plugin accepts batched NV12/RGBA buffers from upstream. The NvDsBatchMeta structure must already be attached to the Gst Buffers. The low-level library (libnvds_infer) operates on any of INT8 RGB, BGR, or GRAY data with dimension of Network Height and Network Width. The Gst-nvinfer plugin performs transforms (format conversion and scaling), on the input frame based on network requirements, and passes the transformed data to the low-level library. The low-level library preprocesses the transformed frames (performs normalization and mean subtraction) and produces final float RGB/BGR/GRAY planar data which is passed to the TensorRT engine for inferencing. The output type generated by the low-level library depends on the network type. The pre-processing function is: ``y = net scale factor*(x-mean)`` Where: * x is the input pixel value. It is an int8 with range [0,255]. * mean is the corresponding mean value, read either from the mean file or as offsets[c], where c is the channel to which the input pixel belongs, and offsets is the array specified in the configuration file. It is a float. * net-scale-factor is the pixel scaling factor specified in the configuration file. It is a float. * y is the corresponding output pixel value. It is a float. Gst-nvinfer currently works on the following type of networks: * Multi-class object detection * Multi-label classification * Segmentation (semantic) * Instance Segmentation The Gst-nvinfer plugin can work in two modes: * Primary mode: Operates on full frames * Secondary mode: Operates on objects added in the meta by upstream components When the plugin is operating as a secondary classifier along with the tracker, it tries to improve performance by avoiding re-inferencing on the same objects in every frame. It does this by caching the classification output in a map with the object’s unique ID as the key. The object is inferred upon only when it is first seen in a frame (based on its object ID) or when the size (bounding box area) of the object increases by 20% or more. This optimization is possible only when the tracker is added as an upstream element. Detailed documentation of the TensorRT interface is available at: https://docs.nvidia.com/deeplearning/sdk/tensorrt-developer-guide/index.html The plugin supports the IPlugin interface for custom layers. Refer to section IPlugin Interface for details. The plugin also supports the interface for custom functions for parsing outputs of object detectors and initialization of non-image input layers in cases where there is more than one input layer. Refer to sources/includes/nvdsinfer_custom_impl.h for the custom method implementations for custom models. .. image:: /content/DS_plugin_gst-nvinfer.png :align: center :alt: Gst-nvinfer Downstream components receive a Gst Buffer with unmodified contents plus the metadata created from the inference output of the Gst-nvinfer plugin. The plugin can be used for cascaded inferencing. That is, it can perform primary inferencing directly on input data, then perform secondary inferencing on the results of primary inferencing, and so on. See the sample application deepstream-test2 for more details. Inputs and Outputs ~~~~~~~~~~~~~~~~~~~~ This section summarizes the inputs, outputs, and communication facilities of the Gst-nvinfer plugin. * Inputs * Gst Buffer * NvDsBatchMeta (attaching NvDsFrameMeta) * Caffe Model and Caffe Prototxt * ONNX * UFF file * TLT Encoded Model and Key * Offline: Supports engine files generated by Transfer Learning Toolkit SDK Model converters * Layers: Supports all layers supported by TensorRT, see: https://docs.nvidia.com/deeplearning/sdk/tensorrt-developer-guide/index.html * Control parameters Gst-nvinfer gets control parameters from a configuration file. You can specify this by setting the property config-file-path. For details, see Gst-nvinfer File Configuration Specifications. Other control parameters that can be set through GObject properties are: * Batch size * Inference interval * Attach inference tensor outputs as buffer metadata * Attach instance mask output as in object metadata * The parameters set through the GObject properties override the parameters in the Gst-nvinfer configuration file. * Outputs * Gst Buffer * Depending on network type and configured parameters, one or more of: * NvDsObjectMeta * NvDsClassifierMeta * NvDsInferSegmentationMeta * NvDsInferTensorMeta Features ~~~~~~~~~ The following table summarizes the features of the plugin. .. csv-table:: Gst-nvinfer plugin features :file: ../content/tables/Gst-nvinfer tables/DS_Plugin_gst-nvinfer_features.csv :widths: 30, 30, 30 :header-rows: 1 Gst-nvinfer File Configuration Specifications ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The Gst-nvinfer configuration file uses a “Key File” format described in: https://specifications.freedesktop.org/desktop-entry-spec/latest The [property] group configures the general behavior of the plugin. It is the only mandatory group. The [class-attrs-all] group configures detection parameters for all classes. The [class-attrs-] group configures detection parameters for a class specified by . For example, the [class-attrs-23] group configures detection parameters for class ID 23. This type of group has the same keys as [class-attrs-all]. The following two tables respectively describe the keys supported for [property] groups and [class-attrs-…] groups. .. csv-table:: Gst-nvinfer Property Group Supported Keys :file: ../content/tables/Gst-nvinfer tables/DS_Plugin_gst-nvinfer_propertygrp_keys.csv :widths: 20, 20, 20, 20, 20 :header-rows: 1 .. csv-table:: Gst-nvinfer Class-attributes Group Supported Keys :file: ../content/tables/Gst-nvinfer tables/DS_Plugin_gst-nvinfer_class_attr_grp_keys.csv :widths: 20, 20, 20, 20, 20 :header-rows: 1 Gst Properties ~~~~~~~~~~~~~~~~~ The values set through Gst properties override the values of properties in the configuration file. The application does this for certain properties that it needs to set programmatically. The following table describes the Gst-nvinfer plugin’s Gst properties. .. csv-table:: Gst-nvinfer Gst Properties :file: ../content/tables/Gst-nvinfer tables/DS_Plugin_gst-nvinfer_gst_properties.csv :widths: 25, 25, 25, 25 :header-rows: 1 Tensor Metadata ~~~~~~~~~~~~~~~~ The Gst-nvinfer plugin can attach raw output tensor data generated by a TensorRT inference engine as metadata. It is added as an NvDsInferTensorMeta in the frame_user_meta_list member of NvDsFrameMeta for primary (full frame) mode, or in the obj_user_meta_list member of NvDsObjectMeta for secondary (object) mode. To read or parse inference raw tensor data of output layers ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 1. Enable property output-tensor-meta or enable the same-named attribute in the configuration file for the Gst-nvinfer plugin. 2. When operating as primary GIE, NvDsInferTensorMeta is attached to each frame’s (each NvDsFrameMeta object’s) frame_user_meta_list. When operating as secondary GIE, NvDsInferTensorMeta is attached to each each NvDsObjectMeta object’s obj_user_meta_list. Metadata attached by Gst-nvinfer can be accessed in a GStreamer pad probe attached downstream from the Gst-nvinfer instance. 3. The NvDsInferTensorMeta object’s metadata type is set to NVDSINFER_TENSOR_OUTPUT_META. To get this metadata you must iterate over the NvDsUserMeta user metadata objects in the list referenced by frame_user_meta_list or obj_user_meta_list. For more information about Gst-infer tensor metadata usage, see the source code in sources/apps/sample_apps/deepstream_infer_tensor_meta-test.cpp, provided in the DeepStream SDK samples. Segmentation Metadata ~~~~~~~~~~~~~~~~~~~~~~~~~ The Gst-nvinfer plugin attaches the output of the segmentation model as user meta in an instance of ``NvDsInferSegmentationMeta`` with meta_type set to ``NVDSINFER_SEGMENTATION_META``. The user meta is added to the ``frame_user_meta_list`` member of ``NvDsFrameMeta`` for primary (full frame) mode, or the ``obj_user_meta_list`` member of ``NvDsObjectMeta`` for secondary (object) mode. For guidance on how to access user metadata, see :ref:`user/custom-metadata-label` and `Tensor Metadata`_ sections.