fix: resolve relative file paths to absolute paths in audio source configuration

- Added path resolution logic to handle relative file: paths robustly regardless of current working directory
- Searches for files relative to both server directory and package root
- Returns clear error message when demo audio files cannot be found

src/auracast/server/multicast_server.py

@@ -205,6 +205,27 @@ class StreamerWorker: # TODO: is wraping in this Worker stricly nececcarry ?
             for big in conf.bigs:
                 big.input_format = f"int16le,{capture_rate},{channels}"
 
+        # Resolve relative file: paths to absolute paths (robust against varying cwd)
+        try:
+            server_dir = os.path.dirname(__file__)
+            pkg_root = os.path.dirname(os.path.dirname(__file__))  # .../auracast
+            for big in conf.bigs:
+                if isinstance(big.audio_source, str) and big.audio_source.startswith('file:'):
+                    rel = big.audio_source.split(':', 1)[1]
+                    if not os.path.isabs(rel):
+                        candidates = [
+                            os.path.normpath(os.path.join(server_dir, rel)),
+                            os.path.normpath(os.path.join(pkg_root, rel)),
+                        ]
+                        resolved = next((c for c in candidates if os.path.exists(c)), None)
+                        if resolved:
+                            log.info("Resolved demo file path '%s' -> '%s'", rel, resolved)
+                            big.audio_source = f"file:{resolved}"
+                        else:
+                            raise FileNotFoundError(rel)
+        except Exception as e:
+            raise HTTPException(status_code=400, detail=f"Demo audio file not found or unreadable: {e}")
+
         # Coerce QoS: compute max_transport_latency from RTN if qos_config present
         if getattr(conf, 'qos_config', None) and getattr(conf.qos_config, 'number_of_retransmissions', None) is not None:
             conf.qos_config.max_transport_latency_ms = int(conf.qos_config.number_of_retransmissions) * 10 + 3
@@ -279,6 +300,26 @@ class StreamerWorker: # TODO: is wraping in this Worker stricly nececcarry ?
                 if device_index is None:
                     raise HTTPException(status_code=400, detail=f"Audio device '{device_name}' not found.")
                 big.audio_source = f'device:{device_index}'
+        # Resolve relative file: paths to absolute paths (robust against varying cwd)
+        try:
+            server_dir = os.path.dirname(__file__)
+            pkg_root = os.path.dirname(os.path.dirname(__file__))  # .../auracast
+            for big in conf.bigs:
+                if isinstance(big.audio_source, str) and big.audio_source.startswith('file:'):
+                    rel = big.audio_source.split(':', 1)[1]
+                    if not os.path.isabs(rel):
+                        candidates = [
+                            os.path.normpath(os.path.join(server_dir, rel)),
+                            os.path.normpath(os.path.join(pkg_root, rel)),
+                        ]
+                        resolved = next((c for c in candidates if os.path.exists(c)), None)
+                        if resolved:
+                            log.info("Resolved demo file path '%s' -> '%s'", rel, resolved)
+                            big.audio_source = f"file:{resolved}"
+                        else:
+                            raise FileNotFoundError(rel)
+        except Exception as e:
+            raise HTTPException(status_code=400, detail=f"Demo audio file not found or unreadable: {e}")
         # Coerce QoS: compute max_transport_latency from RTN if qos_config present
         if getattr(conf, 'qos_config', None) and getattr(conf.qos_config, 'number_of_retransmissions', None) is not None:
             conf.qos_config.max_transport_latency_ms = int(conf.qos_config.number_of_retransmissions) * 10 + 3