S2.1 Pro is Fish Audio’s later S2-generation text-to-speech model for expressive narration and conversational voice applications. It improves on S2 Pro in speech quality, latency and throughput while retaining natural-language delivery control and native multi-speaker dialogue. S2.1 Pro and S2.1 Pro Free share the underlying speech model.
For a narrated explanation, supply the finished wording, intended voice and the moments where pace or emphasis should change. For a conversational application, synthesise the response selected by the application and keep its factual content separate from performance direction. For a scripted exchange, define the speakers and their voices before writing their turns. A useful result is a complete audio passage or playable stream whose words, delivery and speaker roles match that brief.
Write the words that should actually be spoken, then place an instruction immediately before the passage whose delivery should change. Square-bracket directions can express a whisper, a pause, a reaction, emphasis or an open-ended speaking style. Put a mid-sentence change where the performance needs it, and follow descriptive directions with actual speech. A useful explainer brief separates its factual wording from the warmth, pace or emphasis desired for the listener.
For one speaker, select a saved voice identifier or provide a reference recording with its transcript. The producer speech guide recommends a clean 10–30-second sample for instant voice conditioning. Choose a reference with the tone and recording quality appropriate to the script, and preserve the same reference across related passages. The voice reference supplies the speaker’s sound; the text and inline directions supply the content and its performance.
Native multi-speaker synthesis uses markers such as <|speaker:0|> and <|speaker:1|> with an ordered array of voice identifiers or separate reference groups. Keep the numeric speaker labels aligned with that ordering. For an instructional exchange, write each speaker’s line and place the delivery direction after the speaker marker where it belongs. This generates a dialogue within one request; it is a different workflow from S1’s separate single-speaker segments and later assembly.
The producer workflow offers MP3, WAV, raw PCM and Opus output, with MP3 as the default. MP3 supports 64, 128 and 192 kbps; WAV and PCM use documented 16-bit mono sample formats, while Opus uses 48 kHz. Choose the format for a retained narration file, streamed playback or a downstream audio pipeline. Keep the complete script and voice selection with the audio so a later edit can address one line without losing the intended performance.
Speed can be adjusted from 0.5 to 2.0 with volume controls. Text normalisation expands English and Chinese numbers for natural reading. Output loudness normalisation defaults to true and is applied to the S2 family; the same field had no effect on S1. S1’s repetition_penalty does not change S2.1 Pro audio, so an old setting should not be treated as an effective control for this model. Review repeated sounds and wording directly rather than relying on a carried-over parameter to establish the result.
Longer scripts are processed in chunks. The documented chunk-length range is 100–300, and max_new_tokens is an audio-token budget per chunk rather than a total-duration guarantee. Previous-chunk conditioning can carry voice context forward. The producer delivery workflow describes complete audio, incremental audio chunks and live text streaming when the script arrives progressively. Choose the consumption method for the application and preserve enough script context for the next passage’s pronunciation and tone.
For a useful final artifact, listen for omitted or repeated words, number pronunciation, speaker changes, pauses and the intensity of the directions. Different voice references can interpret a cue with different strength, so start with a simple directed line before adding competing tags. In multilingual work, supply the target-language script rather than asking the speech model to invent or translate its content. A focused revision changes the line, cue or reference responsible for the mismatch while retaining the parts of the performance that already fit the brief.
", "aboutText": "S2.1 Pro is Fish Audio’s later S2-generation text-to-speech model for expressive narration and conversational voice applications. It improves on S2 Pro in speech quality, latency and throughput while retaining natural-language delivery control and native multi-speaker dialogue. S2.1 Pro and S2.1 Pro Free share the underlying speech model.\n\nFor a narrated explanation, supply the finished wording, intended voice and the moments where pace or emphasis should change. For a conversational application, synthesise the response selected by the application and keep its factual content separate from performance direction. For a scripted exchange, define the speakers and their voices before writing their turns. A useful result is a complete audio passage or playable stream whose words, delivery and speaker roles match that brief.\n\nWrite the words that should actually be spoken, then place an instruction immediately before the passage whose delivery should change. Square-bracket directions can express a whisper, a pause, a reaction, emphasis or an open-ended speaking style. Put a mid-sentence change where the performance needs it, and follow descriptive directions with actual speech. A useful explainer brief separates its factual wording from the warmth, pace or emphasis desired for the listener.\n\nFor one speaker, select a saved voice identifier or provide a reference recording with its transcript. The producer speech guide recommends a clean 10–30-second sample for instant voice conditioning. Choose a reference with the tone and recording quality appropriate to the script, and preserve the same reference across related passages. The voice reference supplies the speaker’s sound; the text and inline directions supply the content and its performance.\n\nNative multi-speaker synthesis uses markers such as <|speaker:0|> and <|speaker:1|> with an ordered array of voice identifiers or separate reference groups. Keep the numeric speaker labels aligned with that ordering. For an instructional exchange, write each speaker’s line and place the delivery direction after the speaker marker where it belongs. This generates a dialogue within one request; it is a different workflow from S1’s separate single-speaker segments and later assembly.\n\nThe producer workflow offers MP3, WAV, raw PCM and Opus output, with MP3 as the default. MP3 supports 64, 128 and 192 kbps; WAV and PCM use documented 16-bit mono sample formats, while Opus uses 48 kHz. Choose the format for a retained narration file, streamed playback or a downstream audio pipeline. Keep the complete script and voice selection with the audio so a later edit can address one line without losing the intended performance.\n\nSpeed can be adjusted from 0.5 to 2.0 with volume controls. Text normalisation expands English and Chinese numbers for natural reading. Output loudness normalisation defaults to true and is applied to the S2 family; the same field had no effect on S1. S1’s repetition_penalty does not change S2.1 Pro audio, so an old setting should not be treated as an effective control for this model. Review repeated sounds and wording directly rather than relying on a carried-over parameter to establish the result.\n\nLonger scripts are processed in chunks. The documented chunk-length range is 100–300, and max_new_tokens is an audio-token budget per chunk rather than a total-duration guarantee. Previous-chunk conditioning can carry voice context forward. The producer delivery workflow describes complete audio, incremental audio chunks and live text streaming when the script arrives progressively. Choose the consumption method for the application and preserve enough script context for the next passage’s pronunciation and tone.\n\nFor a useful final artifact, listen for omitted or repeated words, number pronunciation, speaker changes, pauses and the intensity of the directions. Different voice references can interpret a cue with different strength, so start with a simple directed line before adding competing tags. In multilingual work, supply the target-language script rather than asking the speech model to invent or translate its content. A focused revision changes the line, cue or reference responsible for the mismatch while retaining the parts of the performance that already fit the brief.", "editorialOverlay": { "copy_fields": null, "copy_sha256": null, "copy_source": null, "html_sha256": "0aca213cd2af2b4c52c9d663744855030cee5ed5452261daeeceb3e200bb4cb1", "module_sha256": "ee9dc1c50b1e6a8fb7fa062030fcb4646b9aaaeb08be513b723a5a92a7290f06", "raw_model_unchanged": true, "schema": "ailoot-native-model-editorial-v1" }, "locale": "en", "methods": [ { "html": "fish-audio/s2.1-proFish Audio S2.1 Pro creates expressive multilingual speech and native multi-speaker dialogue, with improvements over S2 Pro in quality, latency and throughput. Direct performance inside the script and use voice references to produce narration or conversational audio.
This description covers the model’s capabilities. Available in Ailoot inputs, outputs and options are listed for the selected method below.
S2.1 Pro is Fish Audio’s later S2-generation text-to-speech model for expressive narration and conversational voice applications. It improves on S2 Pro in speech quality, latency and throughput while retaining natural-language delivery control and native multi-speaker dialogue. S2.1 Pro and S2.1 Pro Free share the underlying speech model.
For a narrated explanation, supply the finished wording, intended voice and the moments where pace or emphasis should change. For a conversational application, synthesise the response selected by the application and keep its factual content separate from performance direction. For a scripted exchange, define the speakers and their voices before writing their turns. A useful result is a complete audio passage or playable stream whose words, delivery and speaker roles match that brief.
Write the words that should actually be spoken, then place an instruction immediately before the passage whose delivery should change. Square-bracket directions can express a whisper, a pause, a reaction, emphasis or an open-ended speaking style. Put a mid-sentence change where the performance needs it, and follow descriptive directions with actual speech. A useful explainer brief separates its factual wording from the warmth, pace or emphasis desired for the listener.
For one speaker, select a saved voice identifier or provide a reference recording with its transcript. The producer speech guide recommends a clean 10–30-second sample for instant voice conditioning. Choose a reference with the tone and recording quality appropriate to the script, and preserve the same reference across related passages. The voice reference supplies the speaker’s sound; the text and inline directions supply the content and its performance.
Native multi-speaker synthesis uses markers such as <|speaker:0|> and <|speaker:1|> with an ordered array of voice identifiers or separate reference groups. Keep the numeric speaker labels aligned with that ordering. For an instructional exchange, write each speaker’s line and place the delivery direction after the speaker marker where it belongs. This generates a dialogue within one request; it is a different workflow from S1’s separate single-speaker segments and later assembly.
The producer workflow offers MP3, WAV, raw PCM and Opus output, with MP3 as the default. MP3 supports 64, 128 and 192 kbps; WAV and PCM use documented 16-bit mono sample formats, while Opus uses 48 kHz. Choose the format for a retained narration file, streamed playback or a downstream audio pipeline. Keep the complete script and voice selection with the audio so a later edit can address one line without losing the intended performance.
Speed can be adjusted from 0.5 to 2.0 with volume controls. Text normalisation expands English and Chinese numbers for natural reading. Output loudness normalisation defaults to true and is applied to the S2 family; the same field had no effect on S1. S1’s repetition_penalty does not change S2.1 Pro audio, so an old setting should not be treated as an effective control for this model. Review repeated sounds and wording directly rather than relying on a carried-over parameter to establish the result.
Longer scripts are processed in chunks. The documented chunk-length range is 100–300, and max_new_tokens is an audio-token budget per chunk rather than a total-duration guarantee. Previous-chunk conditioning can carry voice context forward. The producer delivery workflow describes complete audio, incremental audio chunks and live text streaming when the script arrives progressively. Choose the consumption method for the application and preserve enough script context for the next passage’s pronunciation and tone.
For a useful final artifact, listen for omitted or repeated words, number pronunciation, speaker changes, pauses and the intensity of the directions. Different voice references can interpret a cue with different strength, so start with a simple directed line before adding competing tags. In multilingual work, supply the target-language script rather than asking the speech model to invent or translate its content. A focused revision changes the line, cue or reference responsible for the mismatch while retaining the parts of the performance that already fit the brief.
POST /v1/audio/speechtextaudio| Field | Type | Requirement | Values & limits | Default |
|---|---|---|---|---|
Fieldmodel | Typestring | RequirementRequired | Values & limits fish-audio/s2.1-pro | Default— |
Fieldinput | Typestring | RequirementRequired | Values & limits Minimum length: 1 | Default— |
Fieldvoice | Typestring | RequirementRequired | Values & limits b347db033a6549378b48d00acb0d06cd Minimum length: 1 | Default— |
Fieldresponse_format | Typestring | RequirementOptional | Values & limits mp3, pcm | Defaultpcm |
Fieldprovider | Typeobject | RequirementOptional | Values & limits | Default— |
| Parameter | Contract |
|---|---|
Parametercontent_type | Contractapplication/json |
Parameterrequired | Contractmodel, input, voice |
Parametermaterial_types | Contracttext |
Lifecycle: synchronous_result_then_owned_library
GET /v1/media/tasks/{task_id} · actual returned task_id or media library record
GET /v1/media/assets/{asset_id}/content
GET /v1/media/assets
GET /v1/media/assets/{asset_id}
Tariff references do not add request options. Supported parameters are listed for the selected method.
Match each charge to the conditions shown. Use one rate for each set of alternative configurations.
| Configuration | Rate schedule | Billing unit | Charge |
|---|---|---|---|
| ConfigurationBase token rates | Rate scheduleBase rate | Billing unit— | Charge Input · Input tokens — / 1K tokens Output · Output tokens — / 1K tokens Input · Cache read — / 1K tokens Input · Cache write — / 1K tokens Input · Cache write, 1 hour — / 1K tokens |
| Configurationinput UTF-8 byte | Rate schedule— | Billing unitper input UTF-8 byte | Charge Input · input UTF-8 byte $0.00003 per input UTF-8 byte |
Ailoot reserves an estimated amount before a request. After the result, it settles the final charge from measured usage. Streaming settlement uses the final usage record. How reservation and settlement work →
set -eu\n: "${AILOOT_API_KEY:?Set your Ailoot API key}"\n: "${AILOOT_INPUT_TEXT:?Set the actual documented input value}"\nexport AILOOT_INPUT_TEXT\npython3 - <<'PY_REQUEST'\nimport json,os\nfrom pathlib import Path\nrequest={'model': 'fish-audio/s2.1-pro', 'input': '${ACTUAL_INPUT_TEXT}', 'voice': 'b347db033a6549378b48d00acb0d06cd', 'response_format': 'mp3'}\nrequest['input']=os.environ['AILOOT_INPUT_TEXT']\nPath('request.json').write_text(json.dumps(request,ensure_ascii=False),encoding='utf-8')\nPY_REQUEST\ncurl --fail-with-body --silent --show-error https://api.ailoot.ai/v1/audio/speech \\\n -H "Authorization: Bearer $AILOOT_API_KEY" -H 'Content-Type: application/json' \\\n --data-binary @request.json -D response-headers.txt -o response.bin\n# Retain the complete response and headers, every actual output, original returned identifiers and all usage fields. Recover the original operation without submitting creation again.\nComplete binary audio or original audio_url response, headers and every owned asset.
GET /v1/media/tasks/{task_id}GET /v1/media/assets/{asset_id}/contentGET /v1/media/assetsGET /v1/media/assets/{asset_id}set -eu\n: "${AILOOT_API_KEY:?Set your Ailoot API key}"\ncurl --fail-with-body --silent --show-error https://api.ailoot.ai/v1/media/assets \\\n -H "Authorization: Bearer $AILOOT_API_KEY" -o owned-assets.json\n# Preserve every returned asset and follow its exact signed content URL. Do not construct a signed token.\nKeep every complete returned response, file and content part.
Retain the complete response and headers, every actual output, original returned identifiers and all usage fields. Recover the original operation without submitting creation again.
Keep the returned X-Client-Request-ID for reconciliation. Read only actual returned task_id/asset_id values or the owned media library; never build a task URL from the operation ID and never resubmit creation.
Ailoot Ultra fish-audio/s2.1-pro
Use the method paths shown above.