This project aim is to create a simple Windows Background service in C# code, to perform subsequent Speech-To-Text (STT) process using Azure cloud, on incoming wave file(s), placed in a specific directory. The output will be a txt file with the transcription. The Service user NAudio library to process file with more than 2 audio channels. In that case, channels are separated and only the first is submitted to the Speech to text service.
Possible Improvements:
- Better error handling
- More parameters in the application settings to fine tune behaviour of the service
- Ability to set a different STT Service (i.e. AWS, Google, IBM Watson, etc)
This software works but it's not PRODUCTION READY.
Please read the whole guide until end, you need each detail before starting the service, otherwise you'll become crazy trying to figure out what's wrong.
The code can be launched/debugged from Visual Studio. When you want to package the binaries, you can use the Project Publish -> Publish to Folder feature function to create the deployable version. You can create a self-contained exe package, with all the required .Net core file embedded (portable). You can run this service even on a windows machine without .Net Core framework (obviously, the file has a huge size).
If you want a lighter version and .net Core framework is installed on target machine, use the classic Binary Relese created during compilation.
.Net core 5.0
This project has been built with .Net Core 5.0 framework. Please refer to (https://docs.microsoft.com/en-us/dotnet/core/extensions/windows-service) for information on developing .Net Core 5.0 Background services.
Microsoft Cognitive Services Speech SDK
To interact with cloud Speech services, this software use the c# Speech SDK library from Microsoft. For further info and documentation,go to (https://docs.microsoft.com/en-us/azure/cognitive-services/speech-service/speech-sdk)
NAudio
Due to a specific requirements, processing and transforming wave files BEFORE the submission to the Azure Cloud Speech Services, the service make use of the library NAudio, that sadly requires the service to be built/targeted on Windows platform only. (https://github.com/naudio/NAudio)
Azure gives you 5 hours of free Speech-To-Text. To create your Speech Service resource, follow these steps (Prerequisite, you have at least a trial Azure Subscription):
- Visit this URL, https://portal.azure.com/#blade/HubsExtension/BrowseResource/resourceType/Microsoft.CognitiveServices%2Faccounts
- Press the button "Add Speech Service"
- Fill the values as in the below example. Name is whatever you want. Subscription is your Azure Subscription. Location is the Azure region where your service will be hosted. Pricing Tier can be F0, the free one, but you can create only one free resource for each subscription. S0 is the paid one, but you have always 5 free hour before paying. As Resource Group select an existing one or create a fresh resource group right here.
- Press "Create"
- At the end of deployment, press “Go To Resource”, or open the newly created resource from the specific Resource Group
- Read the Key to be able to use the service. Remember, this is the setting to be placed in the Application Settings file, BEFORE starting the service
If you better prefer, take a look at the official Microsoft Guide to create the Speech service (https://docs.microsoft.com/en-us/azure/cognitive-services/speech-service/overview#create-the-azure-resource)
Once the project is built (or published to a folder), copy the binaries output and place them in a directory of your choice (ex: "c:\Program Files\STTCloudservice")
To install it as a windows service
- open a powershell as administrator
- run the following command, replace binpath with your binaries folder
sc.exe create "Azure Cloud STT Service" binpath=C:\stt-service\AzureCloudSTTService.exeAfter installation, the service Startup mode is Manual. If you want you can change it to Automatic, so the software can start autonomously at each reboot. You can do it from the Windows Services GUI, or via command line
sc.exe config "Azure Cloud STT Service" start=autoYou can start and stop service from the Services Consoles (WIN+R then launch "services.msc")
Alternatively, from the command line
- Start Service
sc.exe start "Azure Cloud STT Service"- Stop Service
sc.exe stop "Azure Cloud STT Service"Before uninstall, please stop the service using above command. then launch
sc.exe delete "Azure Cloud STT Service"The below structure is only an example. Each folder can be in a different path in your machine.
root
│
└───inputFolder
[The folder where you insert wave files to be elaborated]
└───channelSplitFolder
[A temporary working folder. When a wave file has more than 2 channels or it has been recorded at a frequency higher than 16 Khz, here you will find the downsampled version and individual channels (i.e. a 4 channels wave file will be splitted in 4 different mono file)]
└───errorFolder
[if something unexpected happens during the process, the wave file is moved from inputFolder to errorFolder, to avoid reprocessing of the file]
└───outputFolder
[at the end of processing wave file is moved from the input folder in the output folder renamed with a timestamp. A corresponding txt file is created along the wave file with the transcription]
Before starting the service, please change the application settings, at your convenience. Open appsettings.json with yor favourite editor.
Keys description:
-
AzureSTTService - Key : Place your speech service secret key
-
AzureSTTService - Region : Set the region where you provisioned the service (i.e.= westeurope)
-
AzureSTTService - SourceLanguage : Set the language to transcribe from. For a complete list goto column Locale (BCP-47) at (https://docs.microsoft.com/en-us/azure/cognitive-services/speech-service/language-support#speech-to-text)
DO NOT FORGET THE DOUBLE SLASHES IN THE PATHS
-
Folders - InputFolder : The folder where you insert wave files to be elaborated (i.e c:\stt\inputFolder)
-
Folders - OutputFolder : Where you will find original file wav and txt transcription renamed with a timestamp
-
Folders - ErrorFolder : If any error occur, file are moved here from the input folder
-
Folders - ChannelsSplitFolder : Post-Processed audio file (stereo or more channels, frequencies higher than 16 Khz) are placed here for convenience. Directory is cleaned at each transcription.
-
Folders - SingleTxtTranslationTargetFile : A path to a specific txt file. It will always contain the latest transcription and will be overwritten by each processing iteration (i.e "c:\stt\outputfolder\last_transcription.txt")
Classic logging is used, you can find any trace in the windows events consolle. To open (WIN+R -> eventvwr.msc -> OK) or search Event Viewer in the Start Menu
Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.