added voice formulas for mixed text

abogen/voice_formulas.py

@@ -0,0 +1,43 @@
+from constants import VOICES_INTERNAL
+
+# Calls parsing and loads the voice to gpu or cpu
+def get_new_voice(pipeline, formula, use_gpu):
+    try:
+        weighted_voice = parse_voice_formula(pipeline, formula)            
+        device = "cuda" if use_gpu else "cpu"
+        return weighted_voice.to(device)
+    except Exception as e:
+        raise ValueError(f"Failed to create voice: {str(e)}")
+    
+# Parse the formula and get the combined voice tensor        
+def parse_voice_formula(pipeline, formula):
+    """Parse the voice formula string and return the combined voice tensor."""
+    if not formula.strip():
+        raise ValueError("Empty voice formula")
+        
+    # Initialize the weighted sum
+    weighted_sum = None
+    
+    # Split the formula into terms
+    terms = formula.split('+')
+    
+    for term in terms:
+        # Parse each term (format: "0.333 * voice_name")
+        weight, voice_name = term.strip().split('*')
+        weight = float(weight.strip())
+        voice_name = voice_name.strip()
+        
+        # Get the voice tensor
+        # use VOICES_INTERNAL
+        if voice_name not in VOICES_INTERNAL:
+            raise ValueError(f"Unknown voice: {voice_name}")
+            
+        voice_tensor = pipeline.load_single_voice(voice_name)
+        
+        # Add to weighted sum
+        if weighted_sum is None:
+            weighted_sum = weight * voice_tensor
+        else:
+            weighted_sum += weight * voice_tensor
+            
+    return weighted_sum