树莓派上用ytdlp下载YouTube音频遇类型错误的排查与解决

问题背景 #

将Discord机器人从Replit迁移到树莓派后，原本正常通过ytdlp提取YouTube音频的功能失效，执行下载命令时触发类型错误。

错误触发场景 #

错误出现在以下命令处理代码的extract_info调用行：

@app_commands.command(
        name="downloadyoutubeaudio",
        description="Download youtube audio as an mp3 (Takes a few seconds)")
@app_commands.describe(youtubevideo="The youtube url or search terms")
async def youtubedownload(self, interaction: discord.Interaction,
                                                    youtubevideo: str):

    await interaction.response.defer(ephemeral=False)
    loop2 = asyncio.get_event_loop()
    try:
        # 错误触发行
        audiodata = await loop2.run_in_executor(
                None, lambda: ytdl.extract_info(youtubevideo, download=True))

        audiofilename = audiodata['title'] + '.mp3'
        await interaction.followup.send(
                file=discord.File('youtubemp3.mp3', filename=audiofilename))

        os.remove('youtubemp3.mp3')

具体报错指向：

audiodata = await loop2.run_in_executor( None, lambda: ytdl.extract_info(youtubevideo, download=True))

尝试修复与矛盾错误 #

尝试对输入参数调用.encode()转换为字节对象，反而触发新错误：

cannot use a string pattern on a bytes-like object

打印确认youtubevideo参数类型为字符串，推测与树莓派字节编码方式有关，但无法定位具体问题。

完整错误栈 #

Command 'downloadyoutubeaudio' raised an exception: TypeError: a bytes-like object is required, not 'str'
Task exception was never retrieved
future: <Task finished name='CommandTree-invoker' coro=<CommandTree._from_interaction.<locals>.wrapper() done, defined at /home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/tree.py:1087> exception=CommandInvokeError("Command 'downloadyoutubeaudio' raised an exception: TypeError: a bytes-like object is required, not 'str'")>
Traceback (most recent call last):
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/commands.py", line 827, in _do_call
    return await self._callback(self.binding, interaction, **params)  # type: ignore
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/Desktop/code/musiccommands.py", line 319, in youtubedownload
    raise e
  File "/home/SamuelDorfman/Desktop/code/musiccommands.py", line 302, in youtubedownload
    audiodata = await loop2.run_in_executor(
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/Desktop/code/musiccommands.py", line 303, in <lambda>
    None, lambda: ytdl.extract_info(video, download=True))
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1594, in extract_info
    return self.__extract_info(url, self.get_info_extractor(key), download, extra_info, process)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1605, in wrapper
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1761, in __extract_info
    return self.process_ie_result(ie_result, download, extra_info)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1840, in process_ie_result
    return self.extract_info(
           ^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1594, in extract_info
    return self.__extract_info(url, self.get_info_extractor(key), download, extra_info, process)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1605, in wrapper
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1761, in __extract_info
    return self.process_ie_result(ie_result, download, extra_info)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1890, in process_ie_result
    return self.__process_playlist(ie_result, download)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1981, in __process_playlist
    'playlist', ie_result, self.prepare_filename(ie_copy, 'pl_infojson'))
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1437, in prepare_filename
    filename = self._prepare_filename(info_dict, tmpl_type=dir_type, outtmpl=outtmpl)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1407, in _prepare_filename
    outtmpl = self._outtmpl_expandpath(outtmpl)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/yt_dlp/YoutubeDL.py", line 1139, in _outtmpl_expandpath
    outtmpl = outtmpl.replace('%%', f'%{sep}%').replace('$$', f'${sep}$')
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: a bytes-like object is required, not 'str'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/tree.py", line 1091, in wrapper
    await self._dispatch_error(interaction, e)
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/tree.py", line 1084, in _dispatch_error
    await self.on_error(interaction, error)
  File "/home/SamuelDorfman/Desktop/code/main.py", line 551, in on_app_command_error
    raise error
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/tree.py", line 1089, in wrapper
    await self._call(interaction)
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/tree.py", line 1252, in _call
    await self.on_error(interaction, e)
  File "/home/SamuelDorfman/Desktop/code/main.py", line 551, in on_app_command_error
    raise error
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/tree.py", line 1248, in _call
    await command._invoke_with_namespace(interaction, namespace)
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/commands.py", line 853, in _invoke_with_namespace
    return await self._do_call(interaction, transformed_values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/SamuelDorfman/.local/lib/python3.11/site-packages/discord/app_commands/commands.py", line 842, in _do_call
    raise CommandInvokeError(self, e) from e
discord.app_commands.errors.CommandInvokeError: Command 'downloadyoutubeaudio' raised an exception: TypeError: a bytes-like object is required, not 'str'

解决方案 #

问题根源在于ytdlp的outtmpl配置项，将其显式设置为字符串格式即可修复：

ytdl_opts = {
    'format': 'bestaudio/best',
    'outtmpl': 'youtubemp3.%(ext)s',  # 关键配置
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'mp3',
        'preferredquality': '192',
    }],
}
ytdl = yt_dlp.YoutubeDL(ytdl_opts)

设置后，树莓派上的下载功能恢复正常。

内容的提问来源于stack exchange，提问作者person