Introducing the new “sound trail” data format

4 min readApr 28, 2020

Introduction

This article is to introduce a new open data standard for geo-locative audio storytelling, and to request feedback from the geolocate community.

The goal is to achieve a (cross platform) standard for production and sharing of geo-locative situated media.

We hope that this initiative will be a game-changer.

Background

Geo-locative storytelling, a form of software driven augmented reality experience, has risen into a genre of its own right in recent times. The term used in this document for geo-locative stories is “soundtrail”.

A soundtrail is geo-spatial based audio experience.

It is a collection of audio stories (usually historic) that are tied to a physical place; so, for example, within a town there may be a dozen or so stories, and they are in different places in the town and one can walk around the town, in and out of the different stories.

There currently exist multiple platforms and mobile phone apps which enable the soundtrail experience. These platforms use their own proprietary format for storage and transmission of the data that defines the soundtrails.

Soundtrails (https://soundtrails.com.au) is one of a number of apps available today that sees audio as a primary element in the immersive locative experience.

What we are trying to achieve here is a platform-independent data format for storing and transmitting geo-locative stories.

Goal of a Open Standard for General Adoption

No open standard exists (to our best knowledge) to date, and this document is to introduce and propose the new “.stx” (Soundtrails XLM) file format which we are intending to use for our app and website, but which we hope will be more widely adopted by the geo-locative storytelling community.

The approach of creating a common standard is intended to dramatically reduce the cost of developing and maintaining these styles of creative works.

It creates a common language for accessing and sharing geo-locative audio works. It takes the emphasis away from developers and platform technologies (which traditionally have been prohibitive in cost and complication), and refocuses back on maps as the containers of the creative work.

This benefits the creatives, sound producers, radio journalists, and place based narrative organisations who are producing the works, and gives the creative people a sense of agency in being able to share their works across a range of platforms.

We hope that this standard will be a game-changer for the geo-locative storytelling industry.

One of the key intentions of this format is to keep the implementation as simple as possible.

.stx File Format Definition

An .stx file is a subset of a .kml file, with some additional extensions.

A .stx file can be loaded into software that can view a .kml without error (although not all the sound trail functionality will work).

<Document>

All properties MUST be inside of a <Document> tag.

Supported properties

Only a subset of the available KML properties are supported by a .stx file.

Soundfields can be represented in a .stx file as either polygons or circles.

Polygons

<Placemark id=”1">
  <Polygon>
    <outerBoundaryIs>
      <LinearRing>
        <coordinates> 
          152.84486,-26.758348 152.84604,-26.758348 152.84604,-26.757237 152.84486,-26.757237 152.84486,-26.758348 
        </coordinates>
      </LinearRing>
    </outerBoundaryIs>
  </Polygon>
</Placemark>

Circles

A circle is a point, with an ExtendedData Data attribute to represent the radius.

<Placemark id=”2">
  <Point>
    <coordinates>152.849538,-26.758128</coordinates>
  </Point>
  <ExtendedData>
    <Data name=”radius”>
      <value>104</radius>
    </Data>
  </ExtendedData>
</Placemark>

Additional extension

The ExtendedData tag is used to include the soundtrail specific information, which allows cross compatibility with standard KML files.

Inside of <Document>

The available tags are :

title
desc
imageBaseUrl
audioBaseUrl
images
mapTilesUrl (This is a URL to a .mbtiles file to be used for displaying the map) OR
mapImageOverlayUrl (An option image to use for overlaying)
mapImageBounds (A geo pair required if mapImageOverlayUrl is set)
author (warning if not present)
copyright (warning if not present)

For example :

<ExtendedData>
  <Data name=”title”>
    <value>Nambour Sound Walk</value>
  </Data>
  <Data name=”desc”>
    <value>
      Drawing together history and heritage, local stories and great original music, the Nambour Heritage Soundtrail is a contemporary take on a truly historical town.
    </value>
  </Data>
    <Data name=”imageBaseUrl”>
      <value>https://soundtrails.com.au/soundwalks/datafiles/images/</value>
  </Data>
  <Data name=”images”>
    <value>
      soundwalk_image_596457907caef, soundwalk_image_596457b1a0841, soundwalk_image_596457d396bce, soundwalk_image_59645808f1741, soundwalk_image_596458482974e, hotspot_image_59768cde8e57d
    </value>
  </Data>
</ExtendedData>

Inside of <Placemark>

radius (for a circle)
title
desc
transcript (text of the audio file, for hearing impared)
audioFileUrl (full URL path, or name relative to audioBaseUrl)
audioLayer (higher layer audio will play over the top of lower) (def: 10)
areaDisplayStyle (if this area is visible on a map, & how displayed (‘area’, ‘none’, ‘pin’, ‘alert’)) (def: ‘area’)
audioPlayerVisibe (BOOL — show the audio player show for this audio) (def: true)
audioLoop (‘never’, ‘on-completed’, ‘on-re-entry’) (def: ‘never’)
audioPlayUntilEnd (BOOL — should audio play until the end even if leaving trigger zone) (def: fase)
audioContinueOnReEntry (BOOL — should the audio continue where it left off when re-entering the area) (def: true)
images (a comma separated list of image file names or full URLS)

For example :

<Placemark id=”336">
  <Point>
    <coordinates>    
      152.9598328471183800,-26.6269910082151250
    </coordinates
  </Point>
    <ExtendedData>
      <Data name=”radius”>
        <value>150</value>
      </Data>
      <Data name=”audioFileUrl”> 
       <value>
https://soundtrails.com.au/soundwalks/datafiles/sounds/sound_file_595082f26d231.mp3
       </value>
      </Data>
      <Data name=”title”>
        <value>Howard St and the Cane Train Haul</value>
      </Data>
      <Data name=”desc”>
        <value>
          Memories of the trains that went past and the chaos that sometime ensued.
         </value>
      </Data>
      <Data name=”images”>
        <value> hotspot_images_5959a829a004b, hotspot_images_5964336951ee9
        </value>
      </Data>
  </ExtendedData>
</Placemark>

Basic Sample

Sample.stx

Feedback

We welcome discussion of this proposed standard.

Links

CoCreations : http://cocreations.com.au/

Kris Randall LinkedIn : https://www.linkedin.com/in/kris-randall-52644234/

Soundtrails : https://soundtrails.com.au/

Feb 2021 Update : Open Source Repo

There is now an Open Source Web Viewer for STX (Soundtrails XML) files

soundtrails/stxViewer

This is an open source, publicly available, really basic, . stx file viewer. This version is released as-is as a…

github.com