Soundtrack SDK | Docs

Table of Contents

• Introduction
• Changelog
• Getting started
• Reference implementation
• Authentication & Pairing
• Upgrade and provisioning
• Approval process and certification
• Release management
• Q&A
• Certification

Introduction

The Soundtrack SDK enables you to build support for Soundtrack on your platform. By combining expert curation and world-class tech, Soundtrack Your Brand provides a beautiful all-in-one solution for streaming music to stores, hotels, restaurants, and other commercial settings.

The SDK is available for selected partners. If you’re interested in becoming one, please reach out to sdk@soundtrackyourbrand.com (applications currently open for opportunities of more than 5000 locations).

This page contains the documentation for the SDK. In order to use it, you will need our latest build (which we will send to you).

Soundtrack SDK is the package containing all code and documentation needed for you to get started. Splayer API is the local API within the SDK, used for initiating and controlling playback.

Unless anything else is communicated by Soundtrack, the application shall be named “Soundtrack Player”.

Api

• Provided as a single shared library, built with a toolchain provided by a partner and with no external dependencies.
• Few entry points, which means faster load times and simple mapping both for dynamic and static linking.
• Extendable API without the need to recompile (unless there are breaking changes).
• Callbacks for audio so you can control your hardware specific needs.

Available actions

• Create and free an Splayer API context.
• Exit the player gracefully (after the next song).
• Player control (play, pause, skip track, set volume).
• Get error list.

Responsibilities

• Soundtrack is responsible for the binary and header file (e.g. libsplayer-x.so and splayerapi-x.h).
• Splayer communicates with Soundtrack’s infrastructure and delivers sound buffers (e.g. PCM data).
• Partner is responsible for all the parts concerning the executable, the actual playback (eg. ALSA).
• Soundtrack provides source code examples as-is and it’s the Partners responsibility to make them work.
• Partner can use any part of the source code example, change and modify them, except splayerapi-x.h
• Partner is responsible to check with Soundtrack’s infrastructure every 15 minutes to see if new releases are available.
• Partner is responsible for providing a toolchain that supports a C++ standard that is at most 5 years old at any given time now and in the future.

Requirements

• A POSIX API compatible OS, that supports TCP sockets, and threads.
• At least 64 MB free RAM for the player to operate in.
• A reasonably strong CPU that could handle our parallel encryption, decoding and digital signal processing.
• A minimum of 4 GB of storage used for offline music and data storage. 8 GB is recommended.
• Partner needs to provide a C++14 capable cross compiler toolchain, and compiler options that we can build our library in a x86-64 linux docker container.
• An onboard RTC with backup battery. In case of a power loss, we cannot play audio until we have a valid system time due to our scheduling, and licensing constraints.

Communication

• Main communication channel with Soundtrack is a shared Slack channel in Soundtracks workspace.
• Partner is responsible to provide a list of relevant people to be invited.

Changelog

Detailed changelog can be found in the SDK package.

Getting started

Prerequisites

Make sure that you have:

• Your vendor secret (provided to you by Soundtrack).
• Your Partner API credentials (provided to you by Soundtrack).
• Access to Soundtrack. Sign up at soundtrackyourbrand.com.

All applications must be in line with the terms & conditions and be certified by Soundtrack (see certification criteria further down on this page).

What’s in the package?

• Header files for Splayer API and ALSA implementation example
• Shared library for Splayer API
• Example implementations for audio output via ALSA or Darwin
• Example source code using ALSA or Darwin
• Example source code using the update service to fetch latest shared library

Note: The package can’t be found on this page. It will be sent to you by Soundtrack. A static library version can be provided. It is not included by default due to the increase in size of the package

Soundtrack - Overview

We highly recommend that you play around with your Soundtrack account so you get an overview of the product prior to using the API. All guides and frequently asked questions regarding Soundtrack can be found on our help pages.

It’s extra important that you understand the hierarchy, where one account (e.g. “Ludwig’s Burgers”) can have multiple locations (e.g. “Flagship restaurant, Stockholm”) which in turn can have multiple sound zones (e.g. “Bar”, “Restaurant area”, “Staff room”).

Each sound zone can only have one device. Soundtrack supports multiple device types (see our help pages to see which ones). The rationale for having multiple sound zones is that you want different music in different parts of the same location. If you want the same music everywhere in the same location you’ll only need one device and then distribute the music with your audio system.

Create a device

Before you can run an application using the SDK, you must create a device using the Partner API. This device will be unique and needs to be paired to a sound zone. A device can only be paired with one sound zone at a time. The Partner API is a GraphQL API and you can run the following to create a device. Note: you need your Partner API credentials to do this step. It only needs to be done once since the pairing code does not change.

1. Go to https://partner.soundtrackyourbrand.com/api/explore (this is just an explore tool, you should of course implement this code where you find it suitable)
2. Add the Authorization header. In the “Value” field, write “Basic <your_credentials>” where <your_credentials> are the Partner API credentials that you should have received from Soundtrack. Ensure that you copy the full base64-token including the == on the end

Example:

Authorization: base64encode(client_id:client_secret)

1. Enter a GraphQL query in the top box

   mutation PartnerCodeCreator($input:GeneratePairingCodesInput!){
    generatePairingCodes(input: $input) {
        codes {
            pairingCode
        }
    }
   }
   

2. Include the query variables

   {
    "input": {
        "description":"ARM64",
        "deviceType": "EMBEDDED",
        "label": "Partnername M324",
        "hardwareIds": ["partner_id_ab12"]
    }
   }
   

   • Change the description to add a description of the specific hardware/platform, so we can distinguish among your devices in case there are any differences in hardware/platform or you come up with a new generation etc.
   • Set deviceType to EMBEDDED (currently not optional)
   • Change the label to the name of your product. This will be shown to users at business.soundtrackyourbrand.com.
   • Change the hardwareIds entry to the hardware_id of your choice. See “Authentication & Pairing” for more info
3. Run the query and you should get a pairing code as output. You will need this code to pair the created device with a specific sound zone later.
4. Write down the hardware_id that you chose (in the example ‘partner_id_ab12’). Write down the pairing code that was output when you ran the query. You can rerun the query if you need to. Supplying an existing hardware id will always return the same pairing code.

Pairing a device with a sound zone

1. Open https://business.soundtrackyourbrand.com.
2. Navigate to “zones”.
3. Use an existing zone or create a new one.
4. Click your zone and pair the device using the “Hardware” tab.
5. Enter the Pairing Code that you got when creating a device.
6. The device should now be paired with this sound zone.

Building and running the example code

1. Open the /src folder. There are several examples showcasing some basic setup of a player application.
2. Edit the example files with the hardware_id you created in the “Create a device” section (“partner_id_ab12” in above example).
3. Supply the vendor secret to the application. This can be done in a few different ways:
   • Set the value directly in vendor_secret
   • Set -DVENDOR_SECRET=xxxx when building with cmake
   • Add the vendor secret directly in the CMakeList.txt file

      add_definitions(-DVENDOR_SECRET=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx)
     

4. Build the project using cmake
5. There will now be several example targets in the build root folder
6. Run the example executable (eg. libsplayer_simple)
7. There should be some console output and music should start playing shortly

libsplayer_alsa
is_playing() = false


alsa_open samp: 44100 channels: 2
Alsa initialized, buffer_size: 88200 period_size: 22050
Couldn't find PCM 'PCM' volume control.
alsa_audio_impl::audio_pause: 0
  9 21:56:36 tyson                    warn             job.cpp:161  Slow timer, seconds: 0.052278248003858607, context: "from: dsp.cpp:344 schedule_setup"
 alsa_audio_impl::audio_pause: 0
ERROR: EBADFD: Let's prepare alsa again
snd_pcm_prepare returned 0

Reference implementation

In the package distributed by SYB, you will find an array of example implementations. Feel free to modify as you wish.

Authentication & Pairing

Splayer API is only aware of Vendor Hardware ID, which is something that you as a vendor chose, and a Vendor Secret that you will get from Soundtrack. The hardware ID is used to generate the Device ID in the Partner API (see Create a Device above). The reason Soundtrack Device ID’s are used for pairing is because they are guaranteed to be unique, even though two vendors might have the same Vendor Hardware ID for two different devices. This way we avoid name clashes for devices.

Upgrade and provisioning

Splayer API is provisioned by Soundtrack’s build systems with rollout limited to a certain percent of all devices, or at a certain time of day considering local time zone of the device. Below are two different endpoints to use to retrieve the latest version of Splayer API for two different platforms (Android ARM 64 bit, Ubuntu 16.04 32 bit).

• https://builds.soundtrackyourbrand.com/remote/android-arm64-sdk/latest
• https://builds.soundtrackyourbrand.com/remote/splayer-i686/latest

The template is basically:

• https://builds.soundtrackyourbrand.com/remote/<platform_name>/latest

{
"id": "QnVpbGQsLDFsZ2g1bW1uNnJrLw..",
"version": "48.17-308",
"link": "https://download.api.soundtrackyourbrand.com/ci-releases/splayer-x86_64/libsplayer-1-48.17-308-splayer-x86_64.so",
"checksum": "9e12bb0ded21711ea1c666dc776b2751febcc01f",
"platform": "splayer-x86_64"
}

The two important fields are version and link, you can disregard all other fields in the JSON.

The checksum is a sha1 hash of the file in the link. Make sure to verify the checksum matches for security and reliability reasons.

To get provisioning working you need to send three HTTP headers. Basically each device sends a Vendor Hardware ID as described above and a Device Vendor ID. In the example below the Vendor Hardware ID is 28cfe91fcc6d.

X-Device-Key-0:eth0
X-Device-Id-0:28cfe91fcc6d
X-Device-Vendor:your_vendor_ID

Example of adding HTTP headers with cURL

char buf[1024];
snprintf(buf, sizeof(buf), "X-Device-Id-0:%s", device_id);

struct curl_slist *chunk = NULL;
chunk = curl_slist_append(chunk, "Accept:");
chunk = curl_slist_append(chunk, "X-Device-Key-0:eth0");
chunk = curl_slist_append(chunk, buf);
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);

Approval process and certification

The application built is to be approved by Soundtrack and shall at all times adhere to the certification criterias (see: Certification).

Release management

This section describes the release management of the player library that we send out once a quarter. Note, that this update does not refer to the SDK itself with updated API, which will be communicated when available and backwards compatibility will be kept as long as possible.

Release SDK player software

The SYB releases contain a pre- and full-release. The pre-release is sent out for the purpose of SDK partner testing and the full-release is the the costumer production release. The SYB releases are taking place once every quarter, which is distributed into following months: November, February, May, August. See SDK Release Calendar for exact dates.

Pre-release

Every quarter the pre-release is sent out to the SDK pre-release channel.

• An email will be sent to you when it’s done.
• Your internal test account will be updated.
• From this day, you have three weeks to flag any issues to Soundtrack. Soundtrack will decide whether or not the issue is a blocker.

Full-release

Three weeks after the pre-release is sent out, the production release is sent out to the full customer base on Wednesday morning 02.00-06.00 (based on each player’s local time).

• An email will be sent to you when it’s scheduled.

Patching SDK player software

In the event of a critical issue and there is a need for a patch release Soundtrack has the possibility to release outside of the normal release schedule. The reason for a patch is either an incident or an important bug.

• Important bugs are classified as something that has direct customer impact, such as audio playback issues, UI bugs or irregular data consumption. Fixes are mostly small and should not affect major parts of the code.
• An incident is when a back-end change may or have already happened, that we will or want to protect us from.

Release schedule

You will get an email notification whenever we are sending out a new release either to your pre-release channel or a full production release. For any questions/issues, just reply back to us.

Here’s the full SDK Release Calendar.

Deprecation of software

We support a release for 6 months. Players running versions older than 6 month will stop music playback. One month in advance, the player is deprecated. The time is based on when the software was released.

Here’s the full SYB Deprecation Schedule.

Unsupported

When a player is unsupported, a device error DEVICE_ERROR_UNSUPPORTED_VERSION is raised on the zone and authentication will fail with http 426 which results in that the player won’t be able to play more music. Mails are being sent out to the concerned customers and it’s possible to filter on “Need player update” in Business to find the right players.

Deprecated

When a player is deprecated, a device error DEVICE_ERROR_SOON_UNSUPPORTED_VERSION is raised on the zone but nothing happens on the player. Mails are being sent out to the concerned customers and it’s possible to filter on “Need player update” in Business to find the right players.

Please note that we can’t say which versions will be deprecated when, as that mainly depends on when that version was released (which can change over time). When we deprecate once a month the next deprecation batch will be decided, which will get the deprecation error (one month in advance of being unsupported). No player newer than 6 month will ever be unsupported from release date.

Q&A

Older version of libstdc++ and ld.so running on the target.

Depending on GCC version you might have an older version of libc, libstdc++ and ld. We are running GCC 6.4 and 7.0 in production.

./libSplayer_alsa: /lib/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by libSplayer.so)
./libSplayer_alsa: /lib/libstdc++.so.6: version `CXXABI_1.3.8' not found (required by libSplayer.so)
./libSplayer_alsa: /lib/libstdc++.so.6: version `GLIBCXX_3.4.19' not found (required by libSplayer.so)
./libSplayer_alsa: /lib/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by libSplayer.so)

If needed, we can link libstdc++ statically to avoid most of the issues, but your target platform needs a compatible libc.so (glibc). Use the same version of libc and libstdc++ on your target as in the toolchain that you provide us. For Linux, you can create them using Yocto or Buildroot. Be aware that we are using atomics from c++ 11, and some gcc toolchains put these in a separate library called libatomic.so. This library is required on the device for our player to run.

Audio stutters

On some hardware we have seen ALSA defaulting to a very small buffer size. A 44.1Khz two channel PCM stream is 88 200 samples/per second. In the below example that’s a context switch 200 times a second (every 5ms). Now a small buffer size is great for low latency, game and sound applications where instant sound feedback is needed on user input. This is not the case for audio streaming. With these small buffers we can’t feed ALSA with audio fast enough, so we will get -EPIPE from snd_pcm_writei().

Alsa initialized, buffer_size: 1323 period_size: 441

Set the ALSA buffer size to at least 1 period (second). For 44.1Khz two channel PCM stream is buffer size 88 200 samples and a period size of 22 050 samples. We have provided the code in callbacks_alsa.c. You could try to set the buffer size to 4 periods instead.

Alsa initialized, buffer_size: 88200 period_size: 22050

Error codes explanation

By calling splayer_get_troubles() you are able to retrieve a list of SYB internal errors. See the example code to know how to do it. These error codes can vary between Splayer versions, but this list is updated whenever a new version is released with changes to them.

Here follows a brief explanation of the current possible errors:

Certification

Background

• The below is applicable to the Soundtrack SDK, not the Soundtrack API
• All applications built using the Soundtrack SDK are to be certified by Soundtrack prior to being shared with customers
• In order to conduct the certification, you need, in addition to the credentials used in the SDK, a Soundtrack test account (subject to Soundtrack T&C and provided by Soundtrack)
• The certification process is developed from a customer experience standpoint. Ease of use is critical

Definitions

• Pair is Soundtrack lingo for connecting the Application with Soundtrack using the Device ID
• Device ID is the Soundtrack generated ID needed for pairing the Application with Soundtrack’s services
• SDK is the APIs and binaries provided by Soundtrack
• Application is the partner built application that contains the SDK

Certification process

• Please note that you need to provide Soundtrack with two pcs of the hardware in order for Soundtrack to do the certification
• Any changes to the hardware will prompt a new certification process
• All tests should pass on a 0.5 Mbps network, unless anything else is stated in the instructions
• The partner shall recommend an SD-card to its client (unless internal storage is used). The same SD-card shall be used for the certification
• The certification shall be as close to the real environment as possible, so if the platform’s normal state is e.g. to have two other applications running at the same time, these shall be running during the certification as well

Poor internet connectivity profiles