Implementation:Obss Sahi Download Mmdet Config

Knowledge Sources	Obss_Sahi MMDetection
Domains	Object_Detection, Model_Setup
Last Updated	2026-02-08 12:00 GMT

Overview

Utility functions for downloading MMDetection model weights, configuration files, and resolving nested config inheritance hierarchies.

Description

The sahi.utils.mmdet module provides helper functions for downloading and setting up MMDetection models. MmdetTestConstants defines URLs and local paths for standard test models (Cascade Mask R-CNN, RetinaNet, YOLOX-Tiny). Dedicated download functions handle each model variant. The download_mmdet_config function is the most complex: it downloads a primary config file from the MMDetection GitHub repository, recursively fetches all inherited _base_ configs, and merges them into a single flat config file using mmengine.Config.

Usage

Use these utilities when setting up MMDetection models for use with SAHI. The download_mmdet_config function is particularly useful for obtaining ready-to-use config files without cloning the entire MMDetection repository.

Code Reference

Source Location

• Repository: Obss_Sahi
• File: sahi/utils/mmdet.py
• Lines: 1-189

Signature

def mmdet_version_as_integer() -> int: ...

class MmdetTestConstants:
    MMDET_CASCADEMASKRCNN_MODEL_URL: str
    MMDET_CASCADEMASKRCNN_MODEL_PATH: str
    MMDET_RETINANET_MODEL_URL: str
    MMDET_RETINANET_MODEL_PATH: str
    MMDET_YOLOX_TINY_MODEL_URL: str
    MMDET_YOLOX_TINY_MODEL_PATH: str
    MMDET_CASCADEMASKRCNN_CONFIG_PATH: str
    MMDET_RETINANET_CONFIG_PATH: str
    MMDET_YOLOX_TINY_CONFIG_PATH: str

def download_mmdet_cascade_mask_rcnn_model(destination_path: str | None = None) -> None: ...
def download_mmdet_retinanet_model(destination_path: str | None = None) -> None: ...
def download_mmdet_yolox_tiny_model(destination_path: str | None = None) -> None: ...

def download_mmdet_config(
    model_name: str = "cascade_rcnn",
    config_file_name: str = "cascade_mask_rcnn_r50_fpn_1x_coco.py",
    verbose: bool = True,
) -> str:
    """Downloads and merges MMDetection config files.

    Returns:
        (str) abs path of the downloaded config file.
    """

Import

from sahi.utils.mmdet import (
    download_mmdet_config,
    download_mmdet_cascade_mask_rcnn_model,
    MmdetTestConstants,
)

I/O Contract

Inputs (download_mmdet_config)

Name	Type	Required	Description
model_name	str	No (default "cascade_rcnn")	MMDetection model family name
config_file_name	str	No	Main config filename to download
verbose	bool	No (default True)	Print save path on completion

Outputs

Name	Type	Description
config_path	str	Absolute path to the merged config file
Config file	File	Single merged MMDetection config at mmdet_configs/{version}/{model}/

Usage Examples

Download MMDetection Config

from sahi.utils.mmdet import download_mmdet_config

# Download and merge Cascade Mask R-CNN config
config_path = download_mmdet_config(
    model_name="cascade_rcnn",
    config_file_name="cascade_mask_rcnn_r50_fpn_1x_coco.py",
)
print(f"Config saved to: {config_path}")

Download Model Weights

from sahi.utils.mmdet import download_mmdet_retinanet_model

# Download RetinaNet weights to default path
download_mmdet_retinanet_model()

# Or specify custom destination
download_mmdet_retinanet_model(destination_path="/models/retinanet.pth")

Related Pages

• Environment:Obss_Sahi_Python_Detection_Frameworks