fix vocoder train

cosyvoice/flow/length_regulator.py

@@ -51,6 +51,7 @@ class InterpolateRegulator(nn.Module):
 
     def inference(self, x1, x2, mel_len1, mel_len2, input_frame_rate=50):
         # in inference mode, interploate prompt token and token(head/mid/tail) seprately, so we can get a clear separation point of mel
+        # NOTE 20 corresponds to token_overlap_len in cosyvoice/cli/model.py
         # x in (B, T, D)
         if x2.shape[1] > 40:
             x2_head = F.interpolate(x2[:, :20].transpose(1, 2).contiguous(), size=int(20 / input_frame_rate * 22050 / 256), mode='linear')