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November 08, 2023

The current landscape of TTS models

Written By

Daniel Sadler


AI/Machine learning


Software Development

Read time

5 minute

In the rapidly evolving world of artificial intelligence and natural language processing, Text-to-Speech (TTS) models have emerged as a powerful technology, reshaping the way we interact with digital content. TTS models have come a long way from the robotic and monotonous voices of the past. Today, they produce remarkably natural and expressive speech, blurring the lines between human and machine-generated voices. In this blog post, we'll explore the current landscape of TTS models, discussing their capabilities, applications, and ongoing developments in this field.
Gone are the days of Microsoft SAM, in recent years there has been a remarkable leap forward in TTS technology thanks to the development of neural TTS models. These models leverage deep learning techniques, particularly recurrent and convolutional neural networks, to generate speech that closely mimics human voices. Neural TTS models can capture nuances in speech, including intonation, cadence, and emotional expression. This transformation has opened up a myriad of applications for TTS technology.
How TTS models can be applied:
1. Accessibility: One of the most significant applications is in making digital content accessible to individuals with visual impairments. Screen readers have been using TTS for a long time, but with the advent of neural TTS, the listening experience has become far more natural and engaging.
2. Virtual assistants: Smart speakers and virtual assistants, such as Amazon's Alexa, Google Assistant, and Apple's Siri, rely on TTS technology to converse with users. The more human-like the voice, the more interactive and enjoyable the user experience.
3. E-learning: TTS technology is revolutionising the e-learning industry by converting text-based educational content into audio, making it easier for learners to absorb information through auditory channels.
4. Content creation: Content creators are using TTS models to narrate audiobooks, podcasts, videos and even game voice overs. These voices can be customised to match the content and tone, providing a consistent and professional sound.
5. Localisation: TTS technology is helping bridge language barriers by enabling text in one language to be converted into natural speech in another. This is particularly useful for global businesses and international communication.
Several TTS models have emerged as leaders in the field. Some of the most prominent ones include:
1. Google's WaveNet: WaveNet was one of the pioneering models that set the bar for natural-sounding TTS. It generates speech at the level of individual waveforms, resulting in extremely high-quality audio.
2. NVIDIA's Tacotron and FastSpeech: These models employ deep learning techniques to generate expressive and natural speech, with a focus on speed and efficiency.
3. Amazon Polly: Amazon's Polly offers a wide range of natural voices for developers to use in applications and services, making it a popular choice for businesses.
4. Microsoft's Azure Cognitive Services: Microsoft's service offers a range of voices, including several that sound remarkably human, and is used for various applications, from accessibility to customer service.
In addition to the commercial TTS models mentioned above, there is a thriving community of open-source TTS models that have made significant contributions to the field:
1. VITS: VITS is a cutting-edge open-source TTS model that leverages variational autoencoders to produce high-quality, expressive speech. It offers flexibility and control over the generated voice, making it a valuable tool for research and application development.
2. GlowTTS: GlowTTS is another noteworthy open-source TTS model that adopts a generative flow approach to generate natural and melodic speech. This model is known for its ability to capture nuances in speech, such as prosody and emotional expression, making it suitable for a wide range of applications.
3. Tacotron: Tacotron, an early open-source TTS model, laid the foundation for many subsequent models in the field. It uses a sequence-to-sequence architecture with attention mechanisms to convert text into speech. While newer models have improved upon their performance, Tacotron remains a valuable resource for those exploring TTS technology.
4. TortoiseTTS: TortoiseTTS is an open-source TTS model that focuses on simplicity and ease of use. It is designed to be accessible to developers who may not have extensive experience in machine learning and speech synthesis. This model is a great entry point for those looking to experiment with TTS technology and create their applications.
These open-source TTS models offer a range of options for researchers, developers, and enthusiasts to work with and enhance the state of the art in text-to-speech synthesis. Their availability has contributed to the rapid development and innovation in the field, enabling a more diverse and accessible landscape for TTS technology.
Coqui/TTS, an open-source project, is an excellent platform for leveraging the power of various open-source TTS models. Coqui/TTS provides a user-friendly and unified framework for training, using, and customising TTS models. It offers pre-trained models, including those based on Tacotron, VITS, GlowTTS and other open-source architectures, allowing users to get started quickly without the need for extensive training. It provides tools and documentation for fine-tuning models, making it possible to adapt them to specific tasks, voices, and languages. This flexibility enables users to create voices that suit their unique requirements, whether it's for accessibility, content creation, virtual assistants, or any other application.


The world of Text-to-Speech (TTS) models has undergone a remarkable transformation. These models have revolutionised the way we interact with digital content, making it more accessible and engaging in a variety of applications.
The landscape of TTS technology, including commercial leaders and open-source innovators, continues to evolve, pushing the boundaries of voice quality and versatility. While this technology has incredible potential, it also raises ethical considerations.
As TTS technology advances, it promises a future where human and machine interactions are more seamless and diverse. The ethical impacts of these advancements are a critical conversation that deserves attention as we navigate this exciting journey towards more natural and expressive speech synthesis.


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