Fix OpenAI TTS by chunking text to respect 4096 char limit

services/podcast_service.py

@@ -104,7 +104,7 @@ def _tts_request(text: str, token: str) -> bytes | None:
 
 
 def _synthesize_audio(lines: list[tuple[str, str]], output_path: Path) -> bool:
-    """Synthesize audio via OpenAI TTS. Returns True on success."""
+    """Synthesize audio via OpenAI TTS. Handles 4096 char limit by chunking."""
     try:
         from openai import OpenAI
 
@@ -116,16 +116,25 @@ def _synthesize_audio(lines: list[tuple[str, str]], output_path: Path) -> bool:
         
         logger.info("TTS: Generating audio for %d lines (%d chars)", len(lines), len(full_text))
         
-        # Call OpenAI TTS API
-        response = client.audio.speech.create(
-            model="tts-1",
-            voice="alloy",  # neutral voice (alternatives: echo, fable, onyx, nova, shimmer)
-            input=full_text,
-        )
+        # OpenAI TTS has 4096 character limit, so chunk the text
+        MAX_CHARS = 4000  # Leave buffer for safety
+        chunks = _chunk_text(full_text, MAX_CHARS)
+        logger.info("Split into %d chunks for TTS", len(chunks))
+        
+        # Generate audio for each chunk and collect them
+        audio_data = b""
+        for i, chunk in enumerate(chunks):
+            logger.info("TTS chunk %d/%d (%d chars)", i + 1, len(chunks), len(chunk))
+            response = client.audio.speech.create(
+                model="tts-1",
+                voice="alloy",  # neutral voice
+                input=chunk,
+            )
+            audio_data += response.content
         
-        # Write response to file
+        # Write combined audio to file
         with open(str(output_path), "wb") as f:
-            f.write(response.content)
+            f.write(audio_data)
         
         file_size = os.path.getsize(str(output_path))
         logger.info("Podcast audio saved to %s (%d bytes)", output_path, file_size)