🐛 fix(av1-transfer): use preexec_fn+os.execvp to rename ffmpeg argv[0]

execve with explicit paths fails on this system (linuxbrew symlink issue).
os.execvp in preexec_fn uses PATH lookup which works, and since it replaces
the child process before subprocess's own exec runs, pipes are inherited correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

av1-transfer/main.py

@@ -19,8 +19,8 @@ AV1 视频批量转码脚本
 import argparse
 import ctypes
 import ctypes.util
+import os
 import queue
-import shlex
 import shutil
 import subprocess
 import sys
@@ -130,21 +130,23 @@ def transcode_one_file(file_info, overall_bar, slot_bars, slot_queue, process_na
             str(output_path),
         ]
 
+        str_args = [str(a) for a in ffmpeg_args]
         if process_name:
-            # 用 bash 的 exec -a 重命名 ffmpeg 进程的 argv[0]
-            # ffmpeg 通过 PATH 查找，避免 execve 直接调用 symlink 的兼容问题
-            shell_args = " ".join(shlex.quote(str(a)) for a in ffmpeg_args)
-            sh = shutil.which("sh") or shutil.which("bash") or "/usr/bin/sh"
+            # fork 后、subprocess 执行 exec 之前，用 os.execvp 替换进程：
+            # - execvp 通过 PATH 查找 ffmpeg（规避 execve 直接调用 symlink 的问题）
+            # - argv[0] 设为别名，ps/top 显示别名而非 ffmpeg
+            # - subprocess 设好的 stdout/stderr pipe 已继承，无需额外处理
+            _pname = process_name
+            _args = str_args
             proc = subprocess.Popen(
-                f"exec -a {shlex.quote(process_name)} ffmpeg {shell_args}",
-                shell=True,
-                executable=sh,
+                ["ffmpeg"] + str_args,
+                preexec_fn=lambda: os.execvp("ffmpeg", [_pname] + _args),
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
             )
         else:
             proc = subprocess.Popen(
-                ["ffmpeg"] + ffmpeg_args,
+                ["ffmpeg"] + str_args,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
             )