Speech Synthesis‎

Introduction

Speech synthesis (also known as text-to-speech or TTS) is the process of converting written text into spoken audio.

In VSDK, speech synthesis is powered by CSDK, which offers a wide range of voices across different languages, genders, and voice quality (Voice quality availability).

Voice Format

For <language>, refer to the table and use the value from the Vsdk-csdk Code column.
For <name>, use the lowercase version of the name shown in VDK-Studio.
For <quality>, you can find this information in VDK-Studio under Resources → Voice.

Engine	Format	Example
vsdk-csdk	`<language>,<name>,<quality>`	`enu,evan,embedded-pro`

SSML Support

VSDK also supports SSML (Speech Synthesis Markup Language), which gives you finer control over how the text is spoken—allowing adjustments such as:

Pronunciation
Pauses
Pitch
Rate
Emphasis

SSML is supported for embedded voices, but not for neural voices (if present in your configuration). Neural voices are more natural-sounding but behave as a black box and do not support markup-based control.

Audio Format

The audio data is a 16-bit signed PCM buffer in Little-Endian format.
It is always mono (1 channel), and the sample rate depends on the engine being used.

Engine	Sample Rate (kHz)
csdk	22050

Sample project

A sample project is available for Speech Synthesis usage with VDK Service (in C# or Python).

Python

Download and extract the zip below
Head inside the project
Create and activate a virtual environment (Python Venv documentation)
Install the project : pip install -e .
Run the script : vdk-synthesis --help

If you see the list of options, you can start your configured VDK Service and interact with it using the options available. For example vdk-synthesis --list will list available voices.

VdkServiceSample-VoiceSynthesis (python).zip

C#

Download and extract the zip below
Open the project solution (.sln)
Set VoiceSynthesis as startup project
Build and run project with the argument “--help”

If you see the list of options, you can start your configured VDK Service and interact with it using the options available. For example --list will list available voices.

VdkServiceSample-VoiceSynthesis (C#).zip