feat: improve audio stream selection and caching

extract.py

@@ -410,6 +410,8 @@ _stems = _derive_stems(INPUT_FILES)
 # ─── Prepare output folder ───
 os.makedirs(OUT_DIR, exist_ok=True)
 
+_audio_stream_selections = []  # track selected stream indices for config
+
 for _file_idx, INPUT_FILE in enumerate(INPUT_FILES):
 
     # ─── Derive output filenames ───
@@ -430,6 +432,7 @@ for _file_idx, INPUT_FILE in enumerate(INPUT_FILES):
             print(f"[audio] {stem}: selected stream {audio_stream}")
         else:
             print(f"[audio] {stem}: no audio selected, skipping audio extraction")
+    _audio_stream_selections.append(audio_stream)
 
     # ─── Extract video-only (duration s, no audio, CPU FFV1 re-encode) ───
     # Only apply fps filter if probed fps differs from target (avoid needless re-timing)
@@ -489,3 +492,34 @@ for _file_idx, INPUT_FILE in enumerate(INPUT_FILES):
 
     print(f"-" * 50)
 print(f"All done. Files are in:", OUT_DIR)
+
+# ─── Save selected audio stream indices to config.toml ───
+if len(_audio_stream_selections) >= 2 and CONFIG_PATH and os.path.exists(CONFIG_PATH):
+    try:
+        with open(CONFIG_PATH, "r") as f:
+            cfg_text = f.read()
+        # Update or add audio_stream_a and audio_stream_b in [extract] section
+        import re
+        def _cfg_set(key: str, val) -> str:
+            nonlocal cfg_text
+            pat = re.compile(rf'(^{key}\s*=\s*).*$')
+            replacement = f'{key} = {val}'
+            if pat.search(cfg_text):
+                cfg_text = pat.sub(replacement, cfg_text, count=1)
+            else:
+                # Insert before the next section header or at end of [extract]
+                ins_pat = re.compile(r'(\[audio\])')
+                if ins_pat.search(cfg_text):
+                    cfg_text = ins_pat.sub(f'{replacement}\n\n\\1', cfg_text, count=1)
+                else:
+                    cfg_text += f"\n{replacement}\n"
+        _cfg_set("audio_stream_a", _audio_stream_selections[0]
+                 if _audio_stream_selections[0] is not None else "null")
+        _cfg_set("audio_stream_b", _audio_stream_selections[1]
+                 if _audio_stream_selections[1] is not None else "null")
+        with open(CONFIG_PATH, "w") as f:
+            f.write(cfg_text)
+        print(f"[config] saved audio_stream_a={_audio_stream_selections[0]}, "
+              f"audio_stream_b={_audio_stream_selections[1]} → {CONFIG_PATH}")
+    except Exception as e:
+        print(f"[config] warn: could not save stream indices: {e}", file=sys.stderr)