SLM Open API Package

Python helpers for streaming measurements and audio from an HBK sound level meter (SLM) through WebXi.

This PyPI package is made for the Open Interface for Sound Level Meter repository. Refer to that repository for more detailed usage information and additional examples.

Install

pip install slm_open_api_package

Or add it to an uv project:

uv add slm_open_api_package

The package requires Python 3.12 or newer and a network connection to a compatible SLM.

Connect To A Device

Give every stream one host, either an IP address or host name:

host = "192.168.1.183"

The bundled examples use set_host() to read a host from a local slm_ip file. If the file is missing, it prompts once and creates it:

from slm_api.helpers import webxi_helper_functions as webxi_helper

host = webxi_helper.set_host(__file__)

Basic Leq Stream

WebXiStreamHandler is the main API. mode="leq" is the default and streams one sequence selected by sequenceID.

from slm_api.enums.sequence_id_enum import SequenceIdEnums
from slm_api.helpers.stream_handlers import WebXiStreamHandler

streamer = WebXiStreamHandler(
	host="192.168.1.183",
	sequenceID=SequenceIdEnums.LAeq.value,
	mode="leq",
	saving="csv",
	saving_path="saved_data/laeq",
)

try:
	streamer.startStream()
except KeyboardInterrupt:
	streamer.stopStream()

stopStream() stops the measurement, removes the device stream, and writes buffered saved data. Supported saving formats are "csv", "json", and "pickle"; their extensions are added automatically.

Multiple Sequences

Based on example_multi.py, use mode="multi" for several enabled broadband sequences in a single stream:

from slm_api.helpers.data_handler import DataHandler
from slm_api.helpers.stream_handlers import WebXiStreamHandler


class PrintHandler(DataHandler):
	def handle(self, *, host, name, value, **data):
		print(f"{host} {name}: {value}")


streamer = WebXiStreamHandler(
	host="192.168.1.183",
	sequenceNames=["LAeq", "LCeq", "LAF"],
	mode="multi",
	saving="json",
	saving_path="saved_data/broadband",
)
streamer.setDataHandler(PrintHandler())

try:
	streamer.startStream()
except KeyboardInterrupt:
	streamer.stopStream()

Enable the requested sequences and frequency weightings on the SLM before starting the stream. Each DataHandler.handle() call receives the source host, name, and value. The saving= handler continues saving when a custom handler is attached.

Fast Logging

Based on fast_log_example.py, use mode="fast_logging" for fast broadband samples:

from slm_api.enums.fast_log_intervals_enum import FastLogInterval
from slm_api.enums.sequence_id_enum import SequenceIdEnums
from slm_api.helpers.stream_handlers import WebXiStreamHandler

streamer = WebXiStreamHandler(
	host="192.168.1.183",
	sequenceID=SequenceIdEnums.FastLAF.value,
	mode="fast_logging",
	fast_logging_interval=FastLogInterval.interval_1000ms.value,
	saving="csv",
	saving_path="saved_data/fast_laf",
)

try:
	streamer.startStream()
except KeyboardInterrupt:
	streamer.stopStream()

Audio

Use the MP3 or FLAC examples for decoded audio samples:

from slm_api.enums.sequence_id_enum import SequenceIdEnums
from slm_api.helpers.stream_handlers import WebXiStreamHandler

streamer = WebXiStreamHandler(
	host="192.168.1.183",
	sequenceID=SequenceIdEnums.MP3Signal.value,
	mode="mp3",
)

The matching flac form uses SequenceIdEnums.FLACSignal.value and mode="flac". Audio setup is enabled by the handler. The SLM can take a few seconds to initialize audio recording when its quality setting changes.

Synchronized Multi-Device Stream

Based on multi_device_flac.py, pass multi_device=True and start/stop the group through the synchronized helpers:

from slm_api.enums.sequence_id_enum import SequenceIdEnums
from slm_api.helpers.stream_handlers import WebXiStreamHandler, start_all_synced, stop_all

hosts = ["192.168.1.183", "192.168.1.216"]
streams = [
	WebXiStreamHandler(
		host=host,
		sequenceID=SequenceIdEnums.MP3Signal.value,
		mode="mp3",
		streamName=f"Audio_{host}",
		multi_device=True,
		saving="csv",
		saving_path=f"saved_data/{host}",
	)
	for host in hosts
]

start_all_synced(streams)

try:
    while True:
        time.sleep(1)
except KeyboardInterrupt:
    stop_all(streams)

stop_all() synchronizes the device measurement stops, flushes saving handlers, and removes each device stream.

Modes

Legacy flags such as mp3=True remain supported, but mode= is preferred. Only select one mode per stream.

## Troubleshooting

- **No values arrive:** Confirm the requested sequences are enabled on the SLM.
- **Audio returns no samples after first enable:** Allow the SLM a few seconds to initialize audio recording before retrying.
- **Saved file is missing:** Call `stopStream()` or `stop_all()`; buffered files are written during shutdown.