Upgrade to RealtimeTTS breaks Piper engine on Windows

[Magnetilo22]

Hi Kolja,

after upgrading RealtimeTTS from 5.7 to 6.0 on Windows Piper engine throws an error:

File "h:\source\RealtimeTTS\tests\piper_test.py", line 19, in
stream = TextToAudioStream(engine)
File "F:.conda\envs\RealtimeTTS\lib\site-packages\RealtimeTTS\text_to_stream.py", line 200, in init
self.load_engine(self.engines[self.engine_index])
File "F:.conda\envs\RealtimeTTS\lib\site-packages\RealtimeTTS\text_to_stream.py", line 215, in load_engine
format, channels, rate = self.engine.get_stream_info()
File "F:.conda\envs\RealtimeTTS\lib\site-packages\RealtimeTTS\engines\piper_engine.py", line 95, in get_stream_info
sample_rate = self._get_sample_rate_from_config()
File "F:.conda\envs\RealtimeTTS\lib\site-packages\RealtimeTTS\engines\piper_engine.py", line 83, in get_sample_rate_from_config
config = json.load(f)
File "F:.conda\envs\RealtimeTTS\lib\json_init.py", line 293, in load
return loads(fp.read(),
File "F:.conda\envs\RealtimeTTS\lib\encodings\cp1252.py", line 23, in decode
return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 1510: character maps to

By default, JSON standard dictates that files should be encoded in UTF-8. However, if you don't specify an encoding in Python's open() function, Python falls back to locale.getpreferredencoding(False). On Mac and Linux, this is usually UTF-8, so the code works fine. On Windows, it's often a local codepage (like cp1252), which cannot decode certain special characters or emojis, resulting in the crash.

Can be easily fixed:

 def _get_sample_rate_from_config(self) -> int:
        """
        Reads the sample rate from the Piper voice configuration file.
        
        Returns:
            int: Sample rate from config, or 16000 as fallback
        """
        if not self.voice or not self.voice.config_file:
            return 16000
        
        try:
            with open(self.voice.config_file, 'r', encoding='utf-8') as f:
                config = json.load(f)
                return config.get('audio', {}).get('sample_rate', 16000)
        except (FileNotFoundError, json.JSONDecodeError, KeyError):
            return 16000

Greetings
Magnetilo

[KoljaB]

Thank you!