Text-to-speech (TTS)

The TTS service converts text to speech using on-device models running fully on the Qualcomm NPU. Audio is returned as raw PCM via HTTP chunked transfer encoding.

Prerequisites

Ensure the Audio Analytics container is deployed and running. See Running the Audio Analytics container for setup instructions.

Available models

Query the models endpoint to get the list of available TTS models and voices:

curl http://localhost:8085/audio-analytics/v1/api/tts/models

The currently available models are:

Model	Language	Native sample rate
`melo-tts-en`	English	44100 Hz
`melo-tts-es`	Spanish	44100 Hz
`melo-tts-zh`	Chinese	44100 Hz
`piper-tts-en`	English	22050 Hz
`piper-tts-de`	German	22050 Hz
`piper-tts-it`	Italian	22050 Hz

Use the name value from the response in your synthesis requests.

Endpoints

Method	Endpoint	Description
`GET`	`/tts/models`	List available TTS models and voices
`POST`	`/tts/synthesize`	Synthesize speech from text
`POST`	`/tts/cancel`	Cancel an in-progress synthesis
`POST`	`/tts/close`	Close the active TTS session

Synthesize speech

curl -X POST http://localhost:8085/audio-analytics/v1/api/tts/synthesize \
  -H "Content-Type: application/json" \
  -d '{
    "text": "Hello, how are you today?",
    "model": "melo-tts-en",
    "language": "en",
    "voice": "default",
    "sample_rate": 44100
  }' \
  --output speech.pcm

Parameters:

text (required): Text to synthesize
model (required): TTS model name
language (optional): Language code (en, es, zh, de, it)
voice (optional): Voice name (default: default)
sample_rate (optional): Output sample rate — 44100, 22050, or 16000 Hz. Audio is resampled if different from the model’s native rate.
parameters.speaking_rate (optional): Speaking speed multiplier, e.g. "0.8" for slower, "1.5" for faster.

Response: Raw PCM audio streamed via HTTP chunked transfer.

TTS returns raw PCM, not WAV. Convert it to WAV before playback.

Speaking rate

Adjust the speaking speed if supported by the model, e.g. "0.8" for slower or "1.5" for faster:

curl -X POST http://localhost:8085/audio-analytics/v1/api/tts/synthesize \
  -H "Content-Type: application/json" \
  -d '{
    "text": "Hello, this is a speech rate test.",
    "model": "melo-tts-en",
    "language": "en",
    "sample_rate": 44100,
    "parameters": {"speaking_rate": "1.5"}
  }' \
  --output speech.pcm

Cancel synthesis

Stop an in-progress synthesis:

curl -X POST http://localhost:8085/audio-analytics/v1/api/tts/cancel

Close

Release TTS resources when done synthesizing:

curl -X POST http://localhost:8085/audio-analytics/v1/api/tts/close

Python example

import requests

def synthesize(text, model="melo-tts-en", language="en", sample_rate=44100):
    url = "http://localhost:8085/audio-analytics/v1/api/tts/synthesize"
    response = requests.post(url, json={
        "text": text,
        "model": model,
        "language": language,
        "sample_rate": sample_rate
    }, timeout=30)
    response.raise_for_status()
    with open("speech.pcm", "wb") as f:
        f.write(response.content)
    print(f"Saved {len(response.content)} bytes to speech.pcm")

synthesize("Hello, how are you today?")

Troubleshooting

PCM won’t play: PCM is raw audio. Convert it to WAV before playback. Poor audio quality: Try a higher sample rate (44100 Hz) or check for special characters in the input text.

IQ-9075 EVK

Prerequisites

Available models

Endpoints

Synthesize speech

Speaking rate

Cancel synthesis

Close

Python example

Troubleshooting

Next steps

Speech recognition

Language translation

​Prerequisites

​Available models

​Endpoints

​Synthesize speech

​Speaking rate

​Cancel synthesis

​Close

​Python example

​Troubleshooting

​Next steps

Speech recognition

Language translation

Prerequisites

Available models

Endpoints

Synthesize speech

Speaking rate

Cancel synthesis

Close

Python example

Troubleshooting

Next steps