Generate thumbnails on CPU and with high niceness

lazy_player/thumbnailer.py

@@ -1,9 +1,11 @@
 from __future__ import annotations
 
 import multiprocessing
+import os
 import sys
 from concurrent.futures import ThreadPoolExecutor
-from typing import TYPE_CHECKING
+from queue import LifoQueue
+from typing import TYPE_CHECKING, Any, cast
 
 from gi.repository import GLib, Gst
 
@@ -32,8 +34,10 @@ class Thumbnailer(ThreadPoolExecutor):
             max_workers=MAX_WORKERS,
         )
 
+        self._work_queue = cast(Any, LifoQueue())
+
     def generate_thumbnail(self, file_item: FileItem):
-        """Schedule thumbnail generation"""
+        """Schedule thumbnail generation."""
 
         if not file_item.full_path.is_file():
             return
@@ -41,39 +45,41 @@ class Thumbnailer(ThreadPoolExecutor):
         if file_item.attempted_thumbnail:
             return
 
-        if self._work_queue.qsize() >= MAX_WORKERS:
-            # print("[thumbnail] Ignoring:", file_item.full_path.name)
-            return
-
-        self.submit(generate_thumbnail_sync, file_item)
+        self.submit(generate_thumbnail_sync_nicely, file_item)
         file_item.attempted_thumbnail = True
 
 
+def generate_thumbnail_sync_nicely(file_item: FileItem):
+    os.nice(19)
+    return generate_thumbnail_sync(file_item)
+
+
 def generate_thumbnail_sync(file_item: FileItem):
     """Generate thumbnail for a single file"""
 
     # print("[thumbnailer] Generate:", file_item.full_path.name)
 
     pipeline_str = (
-        "uridecodebin name=uridecodebin ! "
+        "uridecodebin name=uridecodebin force-sw-decoders=true ! "
         "videoconvert ! "
         "jpegenc quality=85 ! "
         "appsink sync=false name=sink"
     )
 
-    pipeline = Gst.parse_launch(pipeline_str)
-    assert isinstance(pipeline, Gst.Pipeline)
-
-    sink = pipeline.get_by_name("sink")
-    assert isinstance(sink, Gst.Element)
-
-    uridecodebin = pipeline.get_by_name("uridecodebin")
-    assert isinstance(uridecodebin, Gst.Element)
-
-    # Set file URI
-    uridecodebin.set_property("uri", Gst.filename_to_uri(str(file_item.full_path)))
+    pipeline: Gst.Pipeline | None = None
 
     try:
+        pipeline = cast(Gst.Pipeline, Gst.parse_launch(pipeline_str))
+
+        sink = pipeline.get_by_name("sink")
+        assert isinstance(sink, Gst.Element)
+
+        uridecodebin = pipeline.get_by_name("uridecodebin")
+        assert isinstance(uridecodebin, Gst.Element)
+
+        # Set file URI
+        uridecodebin.set_property("uri", Gst.filename_to_uri(str(file_item.full_path)))
+
         # Set pipeline to PAUSED to get duration
         pipeline.set_state(Gst.State.PAUSED)
         pipeline.get_state(Gst.CLOCK_TIME_NONE)
@@ -119,4 +125,5 @@ def generate_thumbnail_sync(file_item: FileItem):
         print("[thumbnailer]", err, file=sys.stderr)
 
     finally:
-        pipeline.set_state(Gst.State.NULL)
+        if pipeline:
+            pipeline.set_state(Gst.State.NULL)