diff --git a/src/blrec/postprocess/postprocessor.py b/src/blrec/postprocess/postprocessor.py
index c8160fa..3bda49f 100644
--- a/src/blrec/postprocess/postprocessor.py
+++ b/src/blrec/postprocess/postprocessor.py
@@ -4,7 +4,7 @@ import asyncio
 import logging
 from contextlib import suppress
 from pathlib import PurePath
-from typing import Any, Awaitable, Dict, Iterator, List, Optional, Union
+from typing import Any, Awaitable, Dict, Final, Iterator, List, Optional, Union
 
 from reactivex.scheduler import ThreadPoolScheduler
 
@@ -48,6 +48,8 @@ class Postprocessor(
     AsyncCooperationMixin,
     SupportDebugMixin,
 ):
+    _worker_semaphore: Final = asyncio.Semaphore(value=1)
+
     def __init__(
         self,
         live: Live,
@@ -127,38 +129,43 @@ class Postprocessor(
 
     @aio_task_with_room_id
     async def _worker(self) -> None:
+
         while True:
             self._status = PostprocessorStatus.WAITING
             self._postprocessing_path = None
             self._postprocessing_progress = None
 
             video_path = await self._queue.get()
-            logger.debug(f'Postprocessing... {video_path}')
 
-            if not await self._is_vaild_flv_file(video_path):
-                logger.warning(f'Invalid flv file: {video_path}')
-                self._queue.task_done()
-                continue
+            async with self._worker_semaphore:
+                logger.debug(f'Postprocessing... {video_path}')
 
-            try:
-                if self.remux_to_mp4:
-                    self._status = PostprocessorStatus.REMUXING
-                    result_path = await self._remux_flv_to_mp4(video_path)
-                elif self.inject_extra_metadata:
-                    self._status = PostprocessorStatus.INJECTING
-                    result_path = await self._inject_extra_metadata(video_path)
-                else:
-                    result_path = video_path
+                if not await self._is_vaild_flv_file(video_path):
+                    logger.warning(f'Invalid flv file: {video_path}')
+                    self._queue.task_done()
+                    continue
 
-                if not self._debug:
-                    await discard_file(extra_metadata_path(video_path), 'DEBUG')
+                try:
+                    if self.remux_to_mp4:
+                        self._status = PostprocessorStatus.REMUXING
+                        result_path = await self._remux_flv_to_mp4(video_path)
+                    elif self.inject_extra_metadata:
+                        self._status = PostprocessorStatus.INJECTING
+                        result_path = await self._inject_extra_metadata(video_path)
+                    else:
+                        result_path = video_path
 
-                self._completed_files.append(result_path)
-                await self._emit('video_postprocessing_completed', self, result_path)
-            except Exception as exc:
-                submit_exception(exc)
-            finally:
-                self._queue.task_done()
+                    if not self._debug:
+                        await discard_file(extra_metadata_path(video_path), 'DEBUG')
+
+                    self._completed_files.append(result_path)
+                    await self._emit(
+                        'video_postprocessing_completed', self, result_path
+                    )
+                except Exception as exc:
+                    submit_exception(exc)
+                finally:
+                    self._queue.task_done()
 
     async def _inject_extra_metadata(self, path: str) -> str:
         try: