--- title: Fish Audio S2.1 Pro | Runware Docs url: https://runware.ai/docs/models/fish-audio-s2-1-pro description: Flagship multilingual text-to-speech with natural language voice control and realtime streaming --- # Fish Audio S2.1 Pro Fish Audio S2.1 Pro is a flagship text-to-speech model built for highly expressive, low-latency speech generation. It supports natural-language bracket cues for emotion and delivery control, multi-speaker dialogue in a single generation, 80+ languages with automatic language detection, and realtime streaming with very fast time to first audio. - **ID**: `fishaudio:s2.1@pro` - **Status**: coming-soon - **Creator**: Fish Audio - **Release Date**: March 1, 2026 - **Capabilities**: Text to Audio ## Compatibility & Validation Inside `speech`, `voice` cannot be used with `voices`. --- `speech.voice` cannot be used with `inputs.referenceVoices`. --- `speech.voices` cannot be used with `inputs.referenceVoices`. ## Request Parameters **API Options** Platform-level options for task execution and delivery. ### [taskType](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-tasktype) - **Type**: `string` - **Required**: true - **Value**: `audioInference` Identifier for the type of task being performed ### [taskUUID](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-taskuuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task. ### [outputType](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-outputtype) - **Type**: `string` - **Default**: `URL` Audio output type. **Allowed values**: `URL` `base64Data` `dataURI` ### [outputFormat](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-outputformat) - **Type**: `string` - **Default**: `MP3` Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities. - \`MP3\`: Compressed audio, smaller file size. - \`WAV\`: Uncompressed, high-quality audio. - \`FLAC\`: Lossless compression. - \`OGG\`: Open-source compressed audio format (Vorbis codec). **Allowed values**: `MP3` `WAV` `FLAC` `OGG` ### [audioSettings](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-audiosettings) - **Path**: `audioSettings.bitrate` - **Type**: `object (3 properties)` Audio encoding settings for controlling the bitrate, number of channels, and sample rate of the generated audio. Only applicable for lossy output formats (`MP3` and `OGG`). When using lossless formats (`WAV` or `FLAC`), this parameter must not be provided. The available sample rates and valid bitrate ranges depend on the output format. For `OGG`, bitrate limits also vary by the number of channels. **MP3 bitrate limits**: Bitrate limits for MP3 are the same regardless of mono or stereo. | Sample Rate | Min Bitrate | Max Bitrate | | --- | --- | --- | | 8,000 Hz | 8 kbps | 64 kbps | | 11,025 Hz | 8 kbps | 64 kbps | | 12,000 Hz | 8 kbps | 64 kbps | | 16,000 Hz | 8 kbps | 160 kbps | | 22,050 Hz | 8 kbps | 160 kbps | | 24,000 Hz | 8 kbps | 160 kbps | | 32,000 Hz | 32 kbps | 320 kbps | | 44,100 Hz | 32 kbps | 320 kbps | | 48,000 Hz | 32 kbps | 320 kbps | **OGG bitrate limits — Mono (1 channel)**: | Sample Rate | Min Bitrate | Max Bitrate | | --- | --- | --- | | 8,000 Hz | 8 kbps | 40 kbps | | 12,000 Hz | 16 kbps | 48 kbps | | 16,000 Hz | 16 kbps | 96 kbps | | 24,000 Hz | 16 kbps | 80 kbps | | 48,000 Hz | 32 kbps | 224 kbps | **OGG bitrate limits — Stereo (2 channels)**: | Sample Rate | Min Bitrate | Max Bitrate | | --- | --- | --- | | 8,000 Hz | 16 kbps | 80 kbps | | 12,000 Hz | 16 kbps | 96 kbps | | 16,000 Hz | 24 kbps | 192 kbps | | 24,000 Hz | 32 kbps | 160 kbps | | 48,000 Hz | 48 kbps | 256 kbps | > [!NOTE] > **Lossless formats**: When `outputFormat` is set to `WAV` or `FLAC`, the `audioSettings` parameter is not available since these formats produce uncompressed or lossless audio with no configurable encoding settings. #### [bitrate](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-audiosettings-bitrate) - **Path**: `audioSettings.bitrate` - **Type**: `integer` - **Min**: `8` Audio bitrate in kbps. #### [channels](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-audiosettings-channels) - **Path**: `audioSettings.channels` - **Type**: `integer` - **Default**: `2` Number of audio channels. 1 for mono, 2 for stereo. **Allowed values**: `1` `2` #### [sampleRate](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-audiosettings-samplerate) - **Path**: `audioSettings.sampleRate` - **Type**: `integer` Audio sample rate in Hz. ### [webhookURL](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-webhookurl) - **Type**: `string` - **Format**: `URI` Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available. **Learn more** (1 resource): - [Webhooks](https://runware.ai/docs/platform/webhooks) (platform) ### [deliveryMethod](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-deliverymethod) - **Type**: `string` - **Default**: `sync` Determines how the API delivers task results. **Allowed values**: - `sync` Returns complete results directly in the API response. - `async` Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse. **Learn more** (1 resource): - [Task Polling](https://runware.ai/docs/platform/task-polling) (platform) ### [uploadEndpoint](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-uploadendpoint) - **Type**: `string` - **Format**: `URI` Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials. **Common use cases:** - **Cloud storage**: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs. - **CDN integration**: Upload to content delivery networks for immediate distribution. ```text // S3 presigned URL for secure upload https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600 // Google Cloud Storage presigned URL https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789 // Custom storage endpoint https://storage.example.com/uploads/generated-image.jpg ``` The content data will be sent as the request body to the specified URL when generation is complete. ### [ttl](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-ttl) - **Type**: `integer` - **Min**: `60` Time-to-live (TTL) in seconds for generated content. Only applies when `outputType` is `URL`. ### [includeCost](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-includecost) - **Type**: `boolean` - **Default**: `false` Include task cost in the response. ### [numberResults](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-numberresults) - **Type**: `integer` - **Min**: `1` - **Max**: `4` - **Default**: `1` Number of results to generate. Each result uses a different seed, producing variations of the same parameters. **Inputs** Input resources for the task (images, audio, etc). These must be nested inside the \`inputs\` object. ### [referenceVoices](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-inputs-referencevoices) - **Path**: `inputs.referenceVoices` - **Type**: `array of objects (2 properties)` Inline voice reference for zero-shot voice cloning. Single-speaker only. #### [audio](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-inputs-referencevoices-audio) - **Path**: `inputs.referenceVoices.audio` - **Type**: `string` - **Required**: true Reference audio clip for the voice to clone (UUID, URL, DataURI, or Base64). Audio duration must be between 1.0 and 90.0 seconds. #### [text](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-inputs-referencevoices-text) - **Path**: `inputs.referenceVoices.text` - **Type**: `string` - **Required**: true - **Min**: `1` - **Max**: `1000` Transcript of the reference audio clip. Must match the spoken content of the reference audio. **Core Parameters** Primary parameters that define the task output. ### [model](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-model) - **Type**: `string` - **Required**: true - **Value**: `fishaudio:s2.1@pro` Identifier of the model to use for generation. ### [speech](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-speech) - **Path**: `speech.text` - **Type**: `object (5 properties)` - **Required**: true Settings for speech generation. #### [text](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-speech-text) - **Path**: `speech.text` - **Type**: `string` - **Required**: true - **Min**: `1` - **Max**: `3000` Text to convert to speech. For multi-speaker dialogue, embed inline speaker tags such as `<|speaker:0|>` and `<|speaker:1|>`. Bracket-style paralinguistic cues such as `[laughs]`, `[sigh]`, `[short pause]`, and `[whispering]` can also be embedded inline. #### [voice](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-speech-voice) - **Path**: `speech.voice` - **Type**: `string` Voice model ID from the Fish Audio voice library or a custom voice. Browse all available voices at https://api.fish.audio/model?page\_size=100&page\_number=1&sort\_by=score. **Allowed values**: - `98655a12fa944e26b274c535e5e03842` Egirl — A cute e-girl to chat with you. - `b347db033a6549378b48d00acb0d06cd` Selene — A meditative female voice. - `bf322df2096a46f18c579d0baa36f41d` Adrian — A steady and reliable narrator. - `933563129e564b19a115bedd57b7406a` Sarah — An engaged speaker. - `536d3a5e000945adb7038665781a4aca` Ethan — A curious explainer. - `e3cd384158934cc9a01029cd7d278634` Laura — A confident female narrator. - `79d0bd3e4e5444b18f7b6d89b5927bf1` Jordan — A motivational speaker. - `9a9cf47702da476aa4629e2506d4a857` Hannah — A conversation specialist. #### [voices](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-speech-voices) - **Path**: `speech.voices` - **Type**: `array of strings` Voice model IDs for multi-speaker dialogue. Speaker tags in `speech.text` such as `<|speaker:0|>` and `<|speaker:1|>` map to the matching array index. #### [volume](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-speech-volume) - **Path**: `speech.volume` - **Type**: `float` - **Default**: `0` Volume adjustment in decibels. `0` = no change. #### [speed](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-speech-speed) - **Path**: `speech.speed` - **Type**: `float` - **Min**: `0.5` - **Max**: `2` - **Step**: `0.01` - **Default**: `1` Playback speed of the generated speech. **Settings** Technical parameters to fine-tune the inference process. These must be nested inside the \`settings\` object. ### [temperature](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-temperature) - **Path**: `settings.temperature` - **Type**: `float` - **Min**: `0` - **Max**: `1` - **Step**: `0.01` - **Default**: `0.7` Expressiveness of the generated speech. ### [topP](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-topp) - **Path**: `settings.topP` - **Type**: `float` - **Min**: `0.0001` - **Max**: `1` - **Step**: `0.01` - **Default**: `0.7` Nucleus sampling parameter that controls diversity by limiting the probability mass. Lower values make outputs more focused, higher values increase diversity. ### [chunkLength](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-chunklength) - **Path**: `settings.chunkLength` - **Type**: `integer` - **Min**: `100` - **Max**: `300` - **Default**: `300` Text segment size for processing. ### [conditionOnPreviousChunks](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-conditiononpreviouschunks) - **Path**: `settings.conditionOnPreviousChunks` - **Type**: `boolean` - **Default**: `true` Previous audio context for voice consistency across chunks. ### [earlyStopThreshold](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-earlystopthreshold) - **Path**: `settings.earlyStopThreshold` - **Type**: `float` - **Min**: `0` - **Max**: `1` - **Default**: `1` Early stopping threshold for batch processing. ### [latency](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-latency) - **Path**: `settings.latency` - **Type**: `string` - **Default**: `normal` Latency / quality trade-off. **Allowed values**: - `low` Fastest response, lower quality. - `normal` Balanced default. - `balanced` Highest quality, slower. ### [maxTokens](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-maxtokens) - **Path**: `settings.maxTokens` - **Type**: `integer` - **Min**: `1` - **Max**: `4294967295` - **Default**: `1024` Maximum audio tokens to generate per text chunk. ### [minChunkLength](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-minchunklength) - **Path**: `settings.minChunkLength` - **Type**: `integer` - **Min**: `0` - **Max**: `100` - **Default**: `50` Minimum characters before splitting into a new chunk. ### [normalize](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-normalize) - **Path**: `settings.normalize` - **Type**: `boolean` - **Default**: `true` Text normalization for English and Chinese. Improves stability for numbers. ### [normalizeLoudness](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-normalizeloudness) - **Path**: `settings.normalizeLoudness` - **Type**: `boolean` - **Default**: `true` Normalize output loudness for consistent perceived volume. ### [repetitionPenalty](https://runware.ai/docs/models/fish-audio-s2-1-pro#request-settings-repetitionpenalty) - **Path**: `settings.repetitionPenalty` - **Type**: `float` - **Min**: `0` - **Max**: `2` - **Step**: `0.01` - **Default**: `1.2` Penalty for repeating audio patterns. ## Response Parameters ### [taskType](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-tasktype) - **Type**: `string` - **Required**: true - **Value**: `audioInference` Type of the task. ### [taskUUID](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-taskuuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID of the task. ### [audioUUID](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-audiouuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID of the output audio. ### [audioURL](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-audiourl) - **Type**: `string` - **Format**: `URI` URL of the output audio. ### [audioBase64Data](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-audiobase64data) - **Type**: `string` Base64-encoded audio data. ### [audioDataURI](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-audiodatauri) - **Type**: `string` - **Format**: `URI` Data URI of the output audio. ### [seed](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-seed) - **Type**: `integer` The seed used for generation. If none was provided, shows the randomly generated seed. ### [cost](https://runware.ai/docs/models/fish-audio-s2-1-pro#response-cost) - **Type**: `float` Task cost in USD. Present when `includeCost` is set to `true` in the request.