Note

Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts.

Why Join?

Expert Support: Solve post-sale issues and technical challenges with help from our community and team.
Learn & Share: Exchange tips and tutorials to enhance your skills.
Exclusive Previews: Get early access to new product announcements and sneak peeks.
Special Discounts: Enjoy exclusive discounts on our newest products.
Festive Promotions and Giveaways: Take part in giveaways and holiday promotions.

👉 Ready to explore and create with us? Click [here] and join today!

16. STT with Vosk (Offline)

Vosk is a lightweight speech-to-text (STT) engine that supports many languages and runs fully offline on Raspberry Pi. You only need internet access once to download a language model. After that, everything works without a network connection.

In this lesson, we will:

Check the microphone on Raspberry Pi.
Install and test Vosk with a chosen language model.

Before You Start

Make sure you‘ve completed:

Install All the Modules(Important) — Install robot-hat, vilib, pidog modules, then run the script i2samp.sh.

1. Check Your Microphone

Before using speech recognition, make sure your USB microphone works correctly.

List available recording devices:
```
arecord -l
```
Look for a line like card 1: ... device 0.

Record a short sample (replace 1,0 with the numbers you found):

arecord -D plughw:1,0 -f S16_LE -r 16000 -d 3 test.wav

Example: if your device is card 2, device 0, use:

arecord -D plughw:2,0 -f S16_LE -r 16000 -d 3 test.wav

Play it back to confirm the recording:
```
aplay test.wav
```
Adjust microphone volume if needed:
```
alsamixer
```
- Press F6 to select your USB microphone.
- Find the Mic or Capture channel.
- Make sure it is not muted ([MM] means mute, press M to unmute → should show [OO]).
- Use ↑ / ↓ arrow keys to change the recording volume.

2. Test Vosk

Steps to try it out:

Create a new file:

cd ~/pidog/examples
sudo nano test_stt_vosk.py

Copy the example code into it. Press Ctrl+X, then Y, and Enter to save and exit.

from pidog.stt import Vosk

vosk = Vosk(language="en-us")

print(vosk.available_languages)

while True:
    print("Say something")
    result = vosk.listen(stream=False)
    print(result)

Run the program:
```
sudo python3 test_stt_vosk.py
```
The first time you run this code with a new language, Vosk will automatically download the language model (by default it will download the small version). At the same time, it will also print out the list of supported languages. Then you will see:
```
vosk-model-small-en-us-0.15.zip: 100%|███████████████████| 39.3M/39.3M [00:05<00:00, 7.85MB/s]
['ar', 'ar-tn', 'ca', 'cn', 'cs', 'de', 'en-gb', 'en-in', 'en-us', 'eo', 'es', 'fa', 'fr', 'gu', 'hi', 'it', 'ja', 'ko', 'kz', 'nl', 'pl', 'pt', 'ru', 'sv', 'te', 'tg', 'tr', 'ua', 'uz', 'vn']
Say something
```
This means:
- The model file (vosk-model-small-en-us-0.15) has been downloaded.
- The list of supported languages has been printed.
- The system is now listening — say something into the Pidog microphone, and the recognized text will appear in the terminal.
Tips:
- Keep the microphone about 15–30 cm away.
- Pick a model that matches your language and accent.

Streaming Mode (optional)

You can also stream speech continuously to see partial results as you speak:

from pidog.stt import Vosk

vosk = Vosk(language="en-us")

while True:
    print("Say something")
    for result in vosk.listen(stream=True):
        if result["done"]:
            print(f"final:   {result['final']}")
        else:
            print(f"partial: {result['partial']}", end="\r", flush=True)

Troubleshooting

No such file or directory (when running `arecord`)

You may have used the wrong card/device number. Run:
```
arecord -l
```
and replace 1,0 with the numbers shown for your USB microphone.
Recorded file has no sound

Open the mixer and check the microphone volume:
```
alsamixer
```
- Press F6 to select your USB mic.
- Make sure Mic/Capture is not muted ([OO] instead of [MM]).
- Increase the level with ↑.
Vosk does not recognize speech
- Make sure the language code matches your model (e.g. en-us for English, zh-cn for Chinese).
- Keep the microphone 15–30 cm away and avoid background noise.
- Speak clearly and slowly.
High latency / slow recognition
- The default auto-download is a small model (faster, but less accurate).
- If it’s still slow, close other programs to free CPU.