报错现场

报错反复出现，每次解决一个问题，又因为下一个文件找不到而报错。

C:\etc\Python\Python39\python.exe "C:/Program Files/JetBrains/PyCharm 2022.2.2/plugins/python/helpers/pydev/pydevd.py" --multiprocess --qt-support=auto --client 127.0.0.1 --port 51307 --file C:\workplace\github.com\***\sources\medias\BMedia.py 
Connected to pydev debugger (build 222.4167.33)
Traceback (most recent call last):
  File "C:\etc\Python\Python39\lib\subprocess.py", line 951, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "C:\etc\Python\Python39\lib\subprocess.py", line 1420, in _execute_child
    hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
  File "C:\Program Files\JetBrains\PyCharm 2022.2.2\plugins\python\helpers\pydev\_pydev_bundle\pydev_monkey.py", line 578, in new_CreateProcess
    return getattr(_subprocess, original_name)(app_name, patch_arg_str_win(cmd_line), *args)
FileNotFoundError: [WinError 2] 系统找不到指定的文件。
python-BaseException
Backend QtAgg is interactive backend. Turning interactive mode on.

解决办法

Windows 系统

1. 下载安装 ImageMagick ; ffmpeg-release-essentials.zip

2. 设置环境变量

   
   IMAGEMAGICK_BINARY
   FFMPEG_BINARY
   ffmpeg_bin_path

关键代码展示

moviepy.config.py

config_defaults.py 编写了针对 ffmpeg, imagemagick 的默认值获取

import os

FFMPEG_BINARY = os.getenv('FFMPEG_BINARY', 'ffmpeg-imageio')
IMAGEMAGICK_BINARY = os.getenv('IMAGEMAGICK_BINARY', 'auto-detect')

config.py 尝试加载 ffmpeg, imagemagick 资源

if IMAGEMAGICK_BINARY=='auto-detect':
    if os.name == 'nt':
        try:
            key = wr.OpenKey(wr.HKEY_LOCAL_MACHINE, 'SOFTWARE\\ImageMagick\\Current')
            IMAGEMAGICK_BINARY = wr.QueryValueEx(key, 'BinPath')[0] + r"\convert.exe"
            key.Close()
        except:
            IMAGEMAGICK_BINARY = 'unset'
    elif try_cmd(['convert'])[0]:
        IMAGEMAGICK_BINARY = 'convert'
    else:
        IMAGEMAGICK_BINARY = 'unset'
else:
    if not os.path.exists(IMAGEMAGICK_BINARY):
        raise IOError(
            "ImageMagick binary cannot be found at {}".format(
                IMAGEMAGICK_BINARY
            )
        )

    if not os.path.isfile(IMAGEMAGICK_BINARY):
        raise IOError(
            "ImageMagick binary found at {} is not a file".format(
                IMAGEMAGICK_BINARY
            )
        )

    success, err = try_cmd([IMAGEMAGICK_BINARY])
    if not success:
        raise IOError("%s - The path specified for the ImageMagick binary might "
                      "be wrong: %s" % (err, IMAGEMAGICK_BINARY))

moviepy.config_defaults.py

if FFMPEG_BINARY=='ffmpeg-imageio':
    from imageio.plugins.ffmpeg import get_exe
    FFMPEG_BINARY = get_exe()

elif FFMPEG_BINARY=='auto-detect':

    if try_cmd(['ffmpeg'])[0]:
        FFMPEG_BINARY = 'ffmpeg'
    elif try_cmd(['ffmpeg.exe'])[0]:
        FFMPEG_BINARY = 'ffmpeg.exe'
    else:
        FFMPEG_BINARY = 'unset'
else:
    success, err = try_cmd([FFMPEG_BINARY])
    if not success:
        raise IOError(
            str(err) +
            " - The path specified for the ffmpeg binary might be wrong")

很显然， 系统没有指定资源文件时，moviepy会自己尝试加载。只不过找不到的时候抛出异常。

pydub.utils.py

最关键的部分是，pydub借用了avprobe、ffprobe来完成它的逻辑。
而借用的方式就是调用subprocess.Popen创建子线程，直接调用操作系统，执行ffprobe工具。
此处报错找不到文件就是因为在环境中我当时并未配置 ffprobe所在目录，所以Popen在执行命令ffprobe时，自然就作为找不到ffprobe这个文件的异常爆出来了。

def mediainfo_json(filepath, read_ahead_limit=-1):
    """Return json dictionary with media info(codec, duration, size, bitrate...) from filepath
    """
    prober = get_prober_name()
    command_args = [
        "-v", "info",
        "-show_format",
        "-show_streams",
    ]
    try:
        command_args += [fsdecode(filepath)]
        stdin_parameter = None
        stdin_data = None
    except TypeError:
        if prober == 'ffprobe':
            command_args += ["-read_ahead_limit", str(read_ahead_limit),
                             "cache:pipe:0"]
        else:
            command_args += ["-"]
        stdin_parameter = PIPE
        file, close_file = _fd_or_path_or_tempfile(filepath, 'rb', tempfile=False)
        file.seek(0)
        stdin_data = file.read()
        if close_file:
            file.close()

    command = [prober, '-of', 'json'] + command_args
    res = Popen(command, stdin=stdin_parameter, stdout=PIPE, stderr=PIPE)
    output, stderr = res.communicate(input=stdin_data)
    output = output.decode("utf-8", 'ignore')
    stderr = stderr.decode("utf-8", 'ignore')

    info = json.loads(output)
# ... 后续代码省略

这段代码就是他尝试找到系统中的avprobe命令，或者ffprobe命令。 如果都找不到就会警告：我只能使用默认配置，但是可能运行不了~

def get_prober_name():
    """
    Return probe application, either avconv or ffmpeg
    """
    if which("avprobe"):
        return "avprobe"
    elif which("ffprobe"):
        return "ffprobe"
    else:
        # should raise exception
        warn("Couldn't find ffprobe or avprobe - defaulting to ffprobe, but may not work", RuntimeWarning)
        return "ffprobe"

这段代码就是具体寻找的过程了。显然，它遍历了系统环境中配置的路径，所有路径都会尝试找命令，本质上跟在cmd中输入命令，系统查找可以运行的工具是一个逻辑。

def which(program):
    """
    Mimics behavior of UNIX which command.
    """
    # Add .exe program extension for windows support
    if os.name == "nt" and not program.endswith(".exe"):
        program += ".exe"

    envdir_list = [os.curdir] + os.environ["PATH"].split(os.pathsep)

    for envdir in envdir_list:
        program_path = os.path.join(envdir, program)
        if os.path.isfile(program_path) and os.access(program_path, os.X_OK):
            return program_path

再次运行效果

Success Popen: returncode