When I use some postprocessor_args the youtube-dl gives me an AssertionError when it tries to convert

[mateusfmcota]

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Question

Hi, I'm trying to make a code for converting videos with youtube-dl and convert it with ffmpeg after the download but I don't know the reason that when I run it it gives me an assertionError when it will convert the file.

This args is necessary because the webm [https://i.4cdn.org/wsg/1597715032203.webm] that I used for the example didn't work without making some padding if is converted to mp4 and I can cover this use case on the code I'm trying to build but using it in postprocessor_args doesn't work

This is the args I want to add:

-vf "pad=ceil(iw/2)*2:ceil(ih/2)*2"

This is mine ydl_opts:

ydl_opts = {    
                'download_archive': './db',
                'restrictfilenames': True,
                format:[{
                    'max_filesize': '50M'
                }],
                'prefer_ffmpeg': True,
                'postprocessor_args' : '-vf "pad=ceil(iw/2)*2:ceil(ih/2)*2"',
                'postprocessors': [{
                    'key': 'FFmpegVideoConvertor',
                    'preferedformat' : 'mp4'
                }],
                'verbose': True
                # 'extension' : 'mp4'
}

and this is the output I get when I try to download and convert something and gives me the assertion error:

[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2020.09.20
[debug] Python version 3.8.5 (CPython) - Linux-5.8.12-arch1-1-x86_64-with-glibc2.2.5
[debug] exe versions: ffmpeg 4.3.1, ffprobe 4.3.1, rtmpdump 2.4
[debug] Proxy map: {}
[generic] 1597715032203: Requesting header
[debug] Default format spec: bestvideo+bestaudio/best
[debug] Invoking downloader on 'https://i.4cdn.org/wsg/1597715032203.webm'
[download] 1597715032203-1597715032203.webm has already been downloaded
[download] 100% of 2.56MiB
[ffmpeg] Converting video from webm to mp4, Destination: 1597715032203-1597715032203.mp4
Traceback (most recent call last):
  File "bot.py", line 32, in <module>
    ydl.download(['https://i.4cdn.org/wsg/1597715032203.webm'])
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 2018, in download
    res = self.extract_info(
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 808, in extract_info
    return self.process_ie_result(ie_result, download, extra_info)
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 863, in process_ie_result
    return self.process_video_result(ie_result, download=download)
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 1644, in process_video_result
    self.process_info(new_info)
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 2000, in process_info
    self.post_process(filename, info_dict)
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 2065, in post_process
    files_to_delete, info = pp.run(info)
  File "/usr/lib/python3.8/site-packages/youtube_dl/postprocessor/ffmpeg.py", line 368, in run
    self.run_ffmpeg(path, outpath, options)
  File "/usr/lib/python3.8/site-packages/youtube_dl/postprocessor/ffmpeg.py", line 239, in run_ffmpeg
    self.run_ffmpeg_multiple_files([path], out_path, opts)
  File "/usr/lib/python3.8/site-packages/youtube_dl/postprocessor/ffmpeg.py", line 212, in run_ffmpeg_multiple_files
    opts += self._configuration_args()
  File "/usr/lib/python3.8/site-packages/youtube_dl/postprocessor/common.py", line 65, in _configuration_args
    return cli_configuration_args(self._downloader.params, 'postprocessor_args', default)
  File "/usr/lib/python3.8/site-packages/youtube_dl/utils.py", line 4608, in cli_configuration_args
    assert isinstance(ex_args, list)
AssertionError

[s104346]

postprocessor_args must be a list:

                'postprocessor_args': ['-vf', 'pad=ceil(iw/2)*2:ceil(ih/2)*2'],

[mateusfmcota]

postprocessor_args must be a list:
'postprocessor_args': ['-vf', 'pad=ceil(iw/2)*2:ceil(ih/2)*2'],

It worked, thank you a lot