diff --git a/bilix/ffmpeg.py b/bilix/ffmpeg.py
index 3723a5bc..9f495d19 100644
--- a/bilix/ffmpeg.py
+++ b/bilix/ffmpeg.py
@@ -9,14 +9,29 @@
 
 
 async def concat(path_lst: List[Path], output_path: Path, remove=True):
-    with tempfile.NamedTemporaryFile('w', dir=output_path.parent, delete=False) as fp:
+    with tempfile.NamedTemporaryFile(
+        'w', dir=output_path.parent, delete_on_close=False
+    ) as fp:
         for path in path_lst:
             fp.write(f"file '{path.name}'\n")
-        cmd = ['ffmpeg', '-f', 'concat', '-safe', '0', '-i', fp.name, '-c', 'copy', '-loglevel', 'quiet',
-               str(output_path)]
+        fp.close()
+        cmd = [
+            'ffmpeg',
+            '-f',
+            'concat',
+            '-safe',
+            '0',
+            '-i',
+            fp.name,
+            '-c',
+            'copy',
+            '-loglevel',
+            'quiet',
+            '-bitexact',
+            str(output_path),
+        ]
         # print(' '.join(map(lambda x: f'"{x}"', cmd)))
-    await run_process(cmd)
-    os.remove(fp.name)
+        await run_process(cmd)
     if remove:
         for path in path_lst:
             os.remove(path)
@@ -26,8 +41,19 @@ async def combine(path_lst: List[Path], output_path: Path, remove=True):
     cmd = ['ffmpeg']
     for path in path_lst:
         cmd.extend(['-i', str(path)])
-    # for flac, use -strict -2
-    cmd.extend(['-c', 'copy', '-strict', '-2', '-loglevel', 'quiet', str(output_path)])
+    # for flac, use -strict experimental
+    cmd.extend(
+        [
+            '-c',
+            'copy',
+            '-strict',
+            'experimental',
+            '-loglevel',
+            'quiet',
+            '-bitexact',
+            str(output_path),
+        ]
+    )
     # print(' '.join(map(lambda x: f'"{x}"', cmd)))
     await run_process(cmd)
     if remove:
@@ -35,10 +61,29 @@ async def combine(path_lst: List[Path], output_path: Path, remove=True):
             os.remove(path)
 
 
-async def time_range_clip(input_path: Path, start: int, t: int, output_path: Path, remove=True):
-    # for flac, use -strict -2
-    cmd = ['ffmpeg', '-ss', f'{start:.1f}', '-t', f'{t:.1f}', '-i', str(input_path), '-codec', 'copy', '-strict', '-2',
-           '-loglevel', 'quiet', '-f', 'mp4', str(output_path)]
+async def time_range_clip(
+    input_path: Path, start: int, t: int, output_path: Path, remove=True
+):
+    # for flac, use -strict experimental
+    cmd = [
+        'ffmpeg',
+        '-ss',
+        f'{start:.1f}',
+        '-t',
+        f'{t:.1f}',
+        '-i',
+        str(input_path),
+        '-codec',
+        'copy',
+        '-strict',
+        'experimental',
+        '-loglevel',
+        'quiet',
+        '-f',
+        'mp4',
+        '-bitexact',
+        str(output_path),
+    ]
     # print(' '.join(map(lambda x: f'"{x}"', cmd)))
     await run_process(cmd)
     if remove: