What are Open Source Speech Translation Models?
Open source speech translation models are specialized AI systems that convert text into natural-sounding speech across multiple languages. Using advanced deep learning architectures like dual autoregressive transformers and large language model frameworks, they enable seamless cross-lingual communication and content localization. These models democratize access to powerful speech synthesis technology, fostering innovation in applications ranging from video dubbing and accessibility tools to educational platforms and enterprise solutions.
Fish Speech V1.5
Fish Speech V1.5 is a leading open-source text-to-speech (TTS) model employing an innovative DualAR architecture with dual autoregressive transformer design. It supports multiple languages with over 300,000 hours of training data for English and Chinese, and over 100,000 hours for Japanese. In TTS Arena evaluations, it achieved an exceptional ELO score of 1339, with impressive accuracy rates: 3.5% WER and 1.2% CER for English, and 1.3% CER for Chinese characters.
Fish Speech V1.5: Premium Multilingual Performance
Fish Speech V1.5 is a leading open-source text-to-speech (TTS) model employing an innovative DualAR architecture with dual autoregressive transformer design. It supports multiple languages with over 300,000 hours of training data for English and Chinese, and over 100,000 hours for Japanese. In independent evaluations by TTS Arena, the model performed exceptionally well, with an ELO score of 1339. The model achieved outstanding accuracy with a word error rate (WER) of 3.5% and character error rate (CER) of 1.2% for English, and a CER of 1.3% for Chinese characters.
Pros
- Exceptional ELO score of 1339 in TTS Arena evaluations.
- Innovative DualAR architecture for superior performance.
- Extensive multilingual training data (300k+ hours).
Cons
- Higher pricing compared to other models on SiliconFlow.
- May require more computational resources for optimal performance.
Why We Love It
- It delivers industry-leading speech quality with exceptional multilingual support, backed by extensive training data and proven performance metrics.
CosyVoice2-0.5B
CosyVoice 2 is a streaming speech synthesis model based on a large language model, featuring unified streaming/non-streaming framework design. It achieves ultra-low latency of 150ms in streaming mode while maintaining quality identical to non-streaming mode. Compared to version 1.0, it reduced pronunciation errors by 30-50%, improved MOS score from 5.4 to 5.53, and supports Chinese dialects, English, Japanese, Korean with cross-lingual capabilities.
CosyVoice2-0.5B: Ultra-Low Latency Streaming Excellence
CosyVoice 2 is a streaming speech synthesis model based on a large language model, employing a unified streaming/non-streaming framework design. The model enhances speech token codebook utilization through finite scalar quantization (FSQ) and develops a chunk-aware causal streaming matching model. In streaming mode, it achieves ultra-low latency of 150ms while maintaining synthesis quality almost identical to non-streaming mode. Compared to version 1.0, the pronunciation error rate has been reduced by 30%-50%, the MOS score improved from 5.4 to 5.53, and it supports fine-grained control over emotions and dialects including Chinese dialects, English, Japanese, Korean, and cross-lingual scenarios.
Pros
- Ultra-low latency of 150ms in streaming mode.
- 30-50% reduction in pronunciation error rates.
- Improved MOS score from 5.4 to 5.53.
Cons
- Smaller parameter size (0.5B) may limit some capabilities.
- Streaming quality depends on network conditions.
Why We Love It
- It perfectly balances speed and quality, offering real-time streaming capabilities with significant accuracy improvements and extensive language support.
IndexTTS-2
IndexTTS2 is a breakthrough auto-regressive zero-shot Text-to-Speech model designed for precise duration control in large-scale TTS systems. It features disentangled emotional expression and speaker identity control, incorporates GPT latent representations, and includes a soft instruction mechanism based on text descriptions. The model outperforms state-of-the-art zero-shot TTS models in word error rate, speaker similarity, and emotional fidelity across multiple datasets.
IndexTTS-2: Advanced Zero-Shot Control and Emotional Intelligence
IndexTTS2 is a breakthrough auto-regressive zero-shot Text-to-Speech (TTS) model designed to address precise duration control challenges in large-scale TTS systems, particularly for applications like video dubbing. It introduces innovative speech duration control with two modes: explicit token specification for precise duration and free auto-regressive generation. The model achieves disentanglement between emotional expression and speaker identity, enabling independent control via separate prompts. It incorporates GPT latent representations and utilizes a novel three-stage training paradigm to enhance speech clarity in emotional expressions, plus features a soft instruction mechanism based on text descriptions developed by fine-tuning Qwen3.
Pros
- Breakthrough zero-shot capabilities with duration control.
- Independent control over timbre and emotion.
- Novel three-stage training paradigm for clarity.
Cons
- More complex setup due to advanced feature set.
- Requires both input and output pricing on SiliconFlow.
Why We Love It
- It revolutionizes speech synthesis with unprecedented control over duration, emotion, and speaker identity, making it ideal for professional audio production and dubbing applications.
Speech Translation Model Comparison
In this table, we compare 2025's leading open source speech translation models, each with unique strengths. Fish Speech V1.5 offers premium multilingual performance with extensive training data. CosyVoice2-0.5B excels in ultra-low latency streaming with comprehensive language support. IndexTTS-2 provides advanced zero-shot capabilities with emotional and duration control. This comparison helps you choose the right model for your specific speech translation needs.
| Number | Model | Developer | Subtype | SiliconFlow Pricing | Core Strength |
|---|---|---|---|---|---|
| 1 | Fish Speech V1.5 | fishaudio | Text-to-Speech | $15/M UTF-8 bytes | Premium multilingual accuracy |
| 2 | CosyVoice2-0.5B | FunAudioLLM | Text-to-Speech | $7.15/M UTF-8 bytes | Ultra-low latency streaming |
| 3 | IndexTTS-2 | IndexTeam | Audio Generation | $7.15/M UTF-8 bytes | Zero-shot emotional control |
Frequently Asked Questions
Our top three picks for 2025 are Fish Speech V1.5, CosyVoice2-0.5B, and IndexTTS-2. Each of these models stood out for their innovation, multilingual capabilities, and unique approach to solving challenges in text-to-speech synthesis and cross-lingual audio generation.
Our analysis shows different leaders for various needs. Fish Speech V1.5 is the top choice for premium multilingual accuracy with support for English, Chinese, and Japanese. CosyVoice2-0.5B excels for real-time applications with support for Chinese dialects, English, Japanese, Korean, and cross-lingual scenarios. IndexTTS-2 is ideal for applications requiring precise emotional and duration control.