An example of issue copied from repo to repo: https://github.com/jaywalnut310/vits/issues/11 in vits we predict float duration and then convert it to attention steps. So we need to round floats. VITS applies ceil which results in longer duration than original (usually the scale is 0.9). As a result, you need to scale back to match original length https://github.com/jaywalnut310/vits/blob/main/models.py#L511 In glowtts there is extra clamp https://github.com/coqui-ai/TTS/blob/main/TTS/tts/models/glow_tts.py#L351 This thing is copied from repo to repo, fun thing happends in Matcha, where we multiply by length factor after we applied ceil: https://github.com/shivammehta25/Matcha-TTS/blob/main/matcha/models/matcha_tts.py#L122