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14. TTS with Espeak and Pico2Wave

In this lesson, we’ll use two built-in text-to-speech (TTS) engines on Raspberry Pi — Espeak and Pico2Wave — to make the Pidog talk.

These two engines are both simple and run offline, but they sound quite different:

Espeak: very lightweight and fast, but the voice is robotic. You can adjust speed, pitch, and volume.
Pico2Wave: produces a smoother and more natural voice than Espeak, but has fewer options to configure.

You’ll hear the difference in voice quality and features.

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 Espeak

Espeak is a lightweight TTS engine included in Raspberry Pi OS. Its voice sounds robotic, but it is highly configurable: you can adjust volume, pitch, speed, and more.

Steps to try it out:

Create a new file with the command:

cd ~/pidog/examples
sudo nano test_tts_espeak.py

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

from pidog.tts import Espeak

tts = Espeak()

# Optional voice tuning
# tts.set_amp(100)   # 0 to 200
# tts.set_speed(150) # 80 to 260
# tts.set_gap(5)     # 0 to 200
# tts.set_pitch(50)  # 0 to 99

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

Run the program with:
```
sudo python3 test_tts_espeak.py
```
You should hear the Pidog say: “Hello! I’m Espeak TTS.”
Uncomment the voice tuning lines in the code to experiment with how amp, speed, gap, and pitch affect the sound.

Testing Pico2Wave

Pico2Wave produces a more natural, human-like voice than Espeak. It’s simpler to use but less flexible — you can only change the language, not the pitch or speed.

Steps to try it out:

Create a new file with the command:

cd ~/pidog/examples
sudo nano test_tts_pico2wave.py

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

from pidog.tts import Pico2Wave

tts = Pico2Wave()

tts.set_lang('en-US')  # en-US, en-GB, de-DE, es-ES, fr-FR, it-IT

# Quick hello (sanity check)
tts.say("Hello! I'm Pico2Wave TTS.")

Run the program with:
```
sudo python3 test_tts_pico2wave.py
```
You should hear the Pidog say: “Hello! I’m Pico2Wave TTS.”
Try switching the language (for example, es-ES for Spanish) and listen to the difference.

Troubleshooting

No sound when running Espeak or Pico2Wave
- Check that your speakers/headphones are connected and volume is not muted.
- Run a quick test in terminal:
```
espeak "Hello world"
pico2wave -w test.wav "Hello world" && aplay test.wav
```
If you hear nothing, the issue is with audio output, not your Python code.
Espeak voice sounds too fast or too robotic
- Try adjusting the parameters in your code:
```
tts.set_speed(120)   # slower
tts.set_pitch(60)    # different pitch
```
Permission denied when running code
- Try running with sudo:
```
sudo python3 test_tts_espeak.py
```

Comparison: Espeak vs Pico2Wave

Feature	Espeak	Pico2Wave
Voice quality	Robotic, synthetic	More natural, human-like
Languages	Default English	Fewer, but common ones
Adjustable	Yes (speed, pitch, etc.)	No (only language)
Performance	Very fast, lightweight	Slightly slower, heavier