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metamoth

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Metamoth is a Python package for parsing the metadata of AudioMoth files. Check the full documentation at https://metamoth.readthedocs.io.

Motivation

AudioMoth devices store valuable information in the audio file header. This includes the device ID, the date and time of recording, gain settings and battery state. The number of fields in the metadata is growing as new features are added to the AudioMoth firmware.

However, the metadata is not designed to be easily parsed in a programmatic way. The data is stored as a string comment making it difficult to retrieve the individual metadata fields. Additionally, the comment format is not well documented and changes between AudioMoth firmware versions.

This package helps by quickly parsing the metadata and returning an object containing the metadata.

Usage

The metamoth package provides a single function, parse_metadata, which parses the metadata of an AudioMoth file and returns an object containing the metadata.

from metamoth import parse_metadata

metadata = parse_metadata('path/to/file')

The extracted metadata can be accessed as attributes of the object, as shown

duration = metadata.duration_s
path = metadata.path
# etc.

Extracted Metadata

The metadata variable is an object (of type AMMetadata) containing the metadata of the file.

The extracted metadata contains:

  • path: the path of the audio file
  • firmware_version: the firmware version of the AudioMoth that recorded the file. Since the AudioMoth firmware version is not stored in the recording, this is an estimate and may be incorrect.

Media Information

  • duration_s: the duration of the file in seconds.
  • samplerate_hz: the sample rate of the file in Hz.
  • channels: the number of channels in the file.
  • samples: the number of audio samples in the file.

Data extracted from the AudioMoth comment string:

  • datetime: the date and time of the file in a datetime object.
  • timezone: the timezone of the file as a timezone object.
  • audiomoth_id: the ID of the AudioMoth that recorded the file.
  • battery_state_v: the battery state of the AudioMoth that recorded the file in Volts.
  • low_battery: a boolean indicating if the battery state is low.
  • gain: the gain setting of the AudioMoth that recorded the file.
  • comment: the full comment string in the WAV header.

The following fields are only available for some AudioMoth firmware versions. Nonetheless, they are always present in the metadata object, but may be None.

  • recording_state: the recording state of the AudioMoth that recorded the file.
  • temperature_c: the temperature of the AudioMoth in Celsius.
  • amplitude_threshold: information concerning the wether an amplitude threshold was used and the threshold value.
  • frequency_filter: information concerning the wether a frequency filter was used and the filter settings.
  • deployment_id: the deployment ID as set by the user.
  • external_microphone: a boolean indicating if an external microphone was used.
  • minimum_trigger_duration_s: the minimum trigger duration in seconds.
  • frequency_trigger: information concerning the wether a frequency trigger was used and the trigger settings.

The following table shows the fields available for each AudioMoth firmware.

version recording_state temperature_c amplitude_threshold frequency_filter deployment_id external_microphone minimum_trigger_duration_s frequency_trigger
1.0 ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.0.1 ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.1.0 ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.2.0 ✖ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.2.1 ✔ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.2.2 ✔ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.3.0 ✔ ✖ ✖ ✖ ✖ ✖ ✖ ✖
1.4.0 ✔ ✔ ✔ ✔ ✖ ✖ ✖ ✖
1.4.1 ✔ ✔ ✔ ✔ ✖ ✖ ✖ ✖
1.4.2 ✔ ✔ ✔ ✔ ✖ ✖ ✖ ✖
1.4.3 ✔ ✔ ✔ ✔ ✖ ✖ ✖ ✖
1.4.4 ✔ ✔ ✔ ✔ ✖ ✖ ✖ ✖
1.5.0 ✔ ✔ ✔ ✔ ✔ ✔ ✖ ✖
1.6.0 ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✖
1.7.0 ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✖
1.7.1 ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✖
1.8.0 ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔
1.8.1 ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔

Supported AudioMoth Firmware Versions

In the table below you can find the supported AudioMoth firmware versions.

Supported AudioMoth Firmware Versions
Firmware Supported
1.0.0 ✔
1.0.1 ✔
1.1.0 ✔
1.2.0 ✔
1.2.1 ✔
1.2.2 ✔
1.3.0 ✔
1.4.0 ✔
1.4.1 ✔
1.4.2 ✔
1.4.3 ✔
1.4.4 ✔
1.5.0 ✖
1.6.0 ✔
1.7.0 ✖
1.7.1 ✖
1.8.0 ✖
1.8.1 ✖

Support for newer firmware versions is planned, see the CONTRIBUTING section if you want to help!

Performance

The metamoth package is designed to be fast. It extracts all the required information from the first few bytes and avoids loading the audio data. Thus metamoth parsing times are not affected by the size of the audio file.

The following table shows the parsing times of metamoth compared to exif tool.

File Size (MB) metamoth (ms) exiftool (ms) Speedup
7.3 0.0845 80 ~1000x
44 0.0850 91.86 ~1000x

Installation

The metamoth package can be installed using pip:

pip install metamoth

Check the installation section of the documentation for more information.

Documentation

The documentation for the metamoth package is available at https://metamoth.readthedocs.io/en/latest/index.html.