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!

15. TTS with Piper and OpenAI

In the previous lesson, we tried two built-in TTS engines on Raspberry Pi (Espeak and Pico2Wave). Now let’s explore two more powerful options: Piper (offline, neural network-based) and OpenAI TTS (online, cloud-based).

Piper: a local TTS engine that runs offline on Raspberry Pi.
OpenAI TTS: an online service that provides very natural, human-like voices.

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.

Testing Piper

Steps to try it out:

Create a new file:

cd ~/pidog/examples
sudo nano test_tts_piper.py

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

from pidog.tts import Piper

tts = Piper()

# List supported languages
print(tts.available_countrys())

# List models for English (en_us)
print(tts.available_models('en_us'))

# Set a voice model (auto-download if not already present)
tts.set_model("en_US-amy-low")

# Say something
tts.say("Hello! I'm Piper TTS.")

available_countrys(): print supported languages.
available_models(): list available models for that language.
set_model(): set the voice model (downloads automatically if missing).
say(): convert text to speech and play it.

Run the program:
```
sudo python3 test_tts_piper.py
```
The first time you run it, the selected voice model will be downloaded automatically.
- You should then hear the Pidog say: Hello! I'm Piper TTS.
- You can change to another language model by calling set_model() with a different name.

Testing OpenAI TTS

Get and save your API Key

Go to OpenAI Platform and log in. On the API keys page, click Create new secret key.
Fill in the details (Owner, Name, Project, and permissions if needed), then click Create secret key.
Once the key is created, copy it right away — you won’t be able to see it again. If you lose it, you must generate a new one.
In your project folder (for example: /pidog/examples), create a file called secret.py:
```
cd ~/pidog/examples
sudo nano secret.py
```

Paste your key into the file like this:

# secret.py
# Store secrets here. Never commit this file to Git.
OPENAI_API_KEY = "sk-xxx"

Write and Run a Test Program

Create a new file:

cd ~/pidog/examples
sudo nano test_tts_openai.py

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

from pidog.tts import OpenAI_TTS
from secret import OPENAI_API_KEY   # or use the try/except version shown above

# Initialize OpenAI TTS
tts = OpenAI_TTS(api_key=OPENAI_API_KEY)
tts.set_model('gpt-4o-mini-tts')  # low-latency TTS model
tts.set_voice('alloy')            # pick a voice

# Quick hello (sanity check)
tts.say("Hello! I'm OpenAI TTS.")

Run the program:
```
sudo python3 test_tts_openai.py
```
You should hear the Pidog say:

Hello! I'm OpenAI TTS.

Troubleshooting

No module named ‘secret’

This means secret.py is not in the same folder as your Python file. Move secret.py into the same directory where you run the script, e.g.:
```
ls ~/pidog/examples
# Make sure you see both: secret.py and your .py file
```
OpenAI: Invalid API key / 401
- Check that you pasted the full key (starts with sk-) and there are no extra spaces/newlines.
- Ensure your code imports it correctly:
```
from secret import OPENAI_API_KEY
```
- Confirm network access on your Pi (try ping api.openai.com).
OpenAI: Quota exceeded / billing error
- You may need to add billing or increase quota in the OpenAI dashboard.
- Try again after resolving the account/billing issue.
Piper: tts.say() runs but no sound
- Make sure a voice model is actually present:
```
ls ~/.local/share/piper/voices
```
- Confirm your model name matches exactly in code:
```
tts.set_model("en_US-amy-low")
```
- Check the audio output device/volume on your Pi (alsamixer), and that speakers are connected and powered.
ALSA / sound device errors (e.g., “Audio device busy” or “No such file or directory”)
- Close other programs using audio.
- Reboot the Pi if the device stays busy.
- For HDMI vs. headphone jack output, select the correct device in Raspberry Pi OS audio settings.
Permission denied when running Python
- Try with sudo if your environment requires it:
```
sudo python3 test_tts_piper.py
```

Comparison of TTS Engines

Feature comparison: Espeak vs Pico2Wave vs Piper vs OpenAI TTS
Item	Espeak	Pico2Wave	Piper	OpenAI TTS
Runs on	Built-in on Raspberry Pi (offline)	Built-in on Raspberry Pi (offline)	Raspberry Pi / PC (offline, needs model)	Cloud (online, needs API key)
Voice quality	Robotic	More natural than Espeak	Natural (neural TTS)	Very natural / human-like
Controls	Speed, pitch, volume	Limited controls	Choose different voices/models	Choose model and voices
Languages	Many (quality varies)	Limited set	Many voices/languages available	Best in English (others vary by availability)
Latency / speed	Very fast	Fast	Real-time on Pi 4/5 with “low” models	Network-dependent (usually low latency)
Setup	Minimal	Minimal	Download `.onnx` + `.onnx.json` models	Create API key, install client
Best for	Quick tests, basic prompts	Slightly better offline voice	Local projects with better quality	Highest quality, rich voice options