fix: folder endpoint returning same track for different files of the same trackhash

+ fix: chunked streaming. return instead of yield chunks

app/lib/transcoder.py

@@ -0,0 +1,78 @@
+from app.utils.threading import background
+
+
+import subprocess
+
+
+@background
+def start_transcoding(
+    input_path: str, output_path: str, bitrate: str, container_args: list[str], compression_level: int = 12
+):
+    """
+    Starts a background transcoding process for an audio file.
+
+    This function uses FFmpeg to transcode an audio file from one format to another,
+    with specified bitrate and container format. It runs as a background task.
+
+    Args:
+        input_path (str): The path to the input audio file.
+        output_path (str): The path where the transcoded file will be saved.
+        bitrate (str): The desired bitrate for the output file (e.g., "128k").
+        container_args (list[str]): FFmpeg arguments specific to the output container format.
+        compression_level (int): Compression level (0-9, default: 6).
+
+    Returns:
+        None
+
+    Note:
+        This function is decorated with @background, which means it runs asynchronously.
+        The actual transcoding process is handled by FFmpeg in a subprocess.
+        The function will print status messages about the transcoding process.
+    """
+    # Base command
+    command = [
+        "ffmpeg",
+        "-i",
+        input_path,
+        "-map_metadata", "0",  # Add this line to copy metadata
+        "-b:a",
+        bitrate,
+        "-vn",
+        "-compression_level",
+        str(compression_level),
+        # REVIEW: Idk what any flag below this point does!
+        "-movflags",
+        "faststart+frag_keyframe+empty_moov",
+        "-write_xing",
+        "0",
+        "-fflags",
+        "+bitexact",
+    ]
+
+    # Add format-specific parameters
+    command.extend(container_args)
+
+    # Add output path and overwrite flag
+    command.extend([output_path, "-y"])
+
+    process = subprocess.Popen(
+        command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL
+    )
+    print(f"Started transcoding process with PID: {process.pid}")
+
+    try:
+        # Wait for the process to complete
+        process.wait()
+        print(f"Transcoding process (PID: {process.pid}) completed")
+    except KeyboardInterrupt:
+        print(f"Transcoding interrupted. Terminating process (PID: {process.pid})")
+    finally:
+        # Ensure the process is terminated
+        try:
+            process.terminate()
+            process.wait(timeout=5)  # Wait up to 5 seconds for graceful termination
+        except subprocess.TimeoutExpired:
+            print(
+                f"Process (PID: {process.pid}) did not terminate gracefully. Killing..."
+            )
+            process.kill()