Repository: yt-dlp
Issue: Feet9 Support
Labels: site-request,NSFW

### Checklist

- [X] I'm reporting a new site support request
- [X] I've verified that I'm running yt-dlp version **2021.11.10.1**. ([update instructions](https://github.com/yt-dlp/yt-dlp#update))
- [X] I've checked that all provided URLs are alive and playable in a browser
- [X] I've checked that none of provided URLs [violate any copyrights](https://github.com/ytdl-org/youtube-dl#can-you-add-support-for-this-anime-video-site-or-site-which-shows-current-movies-for-free) or contain any [DRM](https://en.wikipedia.org/wiki/Digital_rights_management) to the best of my knowledge
- [X] I've searched the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues including closed ones. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)
- [X] I've read about [sharing account credentials](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#are-you-willing-to-share-account-details-if-needed) and am willing to share it if required

### Region

Global

### Example URLs

Main Video URL: https://www.feet9.com/22978/cute-girlfriends-foot-worship/
Embed URL: https://www.feet9.com/modules/video/player/embed.php?id=22978

Main Video URL: 
Embed URL: https://www.feet9.com/modules/video/player/embed.php?id=13458

### Description

UPDATE: this website is still not supported by generic information extractor. This is a request for dedicated extractor even if it were supported.

### Verbose log

```shell
[debug] Command-line config: ['https://www.feet9.com/13458/amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner/']
[debug] System config file: /etc/yt-dlp.conf
[debug] System config: ['--verbose', '--no-colors', '--output', '/users/User/Downloads/tmp/%(playlist)s/%(playlist_index)s – %(title)s.%(ext)s', '--continue', '--no-part', '--cookies-from-browser', 'Safari', '--socket-timeout', '300', '--geo-bypass', '--no-check-certificate', '--concurrent-fragments', '32768', '--retries', 'infinite', '--fragment-retries', 'infinite', '--buffer-size', '4m', '--http-chunk-size', '16M', '--playlist-reverse', '--hls-prefer-native', '--hls-use-mpegts', '--yes-playlist', '--format', 'bv+ba/b', '--merge-output-format', 'mkv', '--remux-video', 'mkv', '--audio-format', 'best', '--audio-quality', '0', '--embed-subs', '--embed-metadata', '--fixup', 'detect_or_warn', '--extractor-retries', 'infinite']
Cookies redacted.
[Cookies] Extracted 62 cookies from safari
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, err utf-8, pref UTF-8
[debug] yt-dlp version 2021.11.10.1
[debug] Lazy loading extractors is disabled
[debug] Python version 3.9.8 (CPython 64bit) - macOS-12.1-x86_64-i386-64bit
[debug] exe versions: ffmpeg N-104454-gd92fdc7144 (fdk,setts), ffprobe N-104454-gd92fdc7144, phantomjs 2.1.1, rtmpdump 2.4
[debug] Optional libraries: Cryptodome, mutagen, sqlite, websockets
[debug] Proxy map: {}
[debug] [generic] Extracting URL: https://www.feet9.com/13458/amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner/
[generic] amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner: Requesting header
WARNING: [generic] Falling back on generic information extractor.
[generic] amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner: Downloading webpage
[generic] amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner: Extracting information
[debug] Looking for video embeds
[debug] Identified a JSON LD
[info] amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner: Downloading 1 format(s): 0
[debug] Invoking downloader on "https://www.feet9.com/13458/amateur-hottie-licking-her-best-girlfriend-s-lovely-toes-in-sixty-niner/"
[download] Unable to resume
[download] Destination: /users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend's lovely toes in sixty-niner.unknown_video
[download] 100% of 71.18KiB in 00:00      
[VideoRemuxer] Remuxing video from unknown_video to mkv; Destination: /users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend's lovely toes in sixty-niner.mkv
[debug] ffmpeg command line: ffmpeg -y -loglevel repeat+info -i 'file:/users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend'"'"'s lovely toes in sixty-niner.unknown_video' -c copy -map 0 -dn 'file:/users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend'"'"'s lovely toes in sixty-niner.mkv'
[debug] ffmpeg version N-104454-gd92fdc7144 Copyright (c) 2000-2021 the FFmpeg developers
  built with Apple clang version 13.0.0 (clang-1300.0.29.30)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/HEAD-d92fdc7 --enable-shared --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-libaom --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-libsnappy --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-demuxer=dash --enable-opencl --enable-videotoolbox --disable-htmlpages --enable-chromaprint --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfdk-aac --enable-libgme --enable-libgsm --enable-libmodplug --enable-libopenh264 --enable-libopenjpeg --enable-librav1e --enable-librsvg --enable-librtmp --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtesseract --enable-libtwolame --enable-libvidstab --enable-libvmaf --enable-libwebp --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-openssl --enable-nonfree --enable-decklink --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/include --enable-libjack --enable-indev=jack --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb
  libavutil      57.  7.100 / 57.  7.100
  libavcodec     59. 12.100 / 59. 12.100
  libavformat    59.  8.100 / 59.  8.100
  libavdevice    59.  0.101 / 59.  0.101
  libavfilter     8. 16.100 /  8. 16.100
  libswscale      6.  1.100 /  6.  1.100
  libswresample   4.  0.100 /  4.  0.100
  libpostproc    56.  0.100 / 56.  0.100
file:/users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend's lovely toes in sixty-niner.unknown_video: Invalid data found when processing input
ERROR: Postprocessing: file:/users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend's lovely toes in sixty-niner.unknown_video: Invalid data found when processing input
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/YoutubeDL.py", line 2941, in process_info
    info_dict = self.post_process(dl_filename, info_dict, files_to_move)
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/YoutubeDL.py", line 3101, in post_process
    info = self.run_pp(pp, info)
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/YoutubeDL.py", line 3044, in run_pp
    files_to_delete, infodict = pp.run(infodict)
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/postprocessor/common.py", line 22, in run
    ret = func(self, info, *args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/postprocessor/common.py", line 112, in wrapper
    return func(self, info)
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/postprocessor/ffmpeg.py", line 542, in run
    self.run_ffmpeg(filename, outpath, self._options(target_ext))
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/postprocessor/ffmpeg.py", line 315, in run_ffmpeg
    return self.run_ffmpeg_multiple_files([path], out_path, opts, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/postprocessor/ffmpeg.py", line 271, in run_ffmpeg_multiple_files
    return self.real_run_ffmpeg(
  File "/usr/local/lib/python3.9/site-packages/yt_dlp/postprocessor/ffmpeg.py", line 308, in real_run_ffmpeg
    raise FFmpegPostProcessorError(stderr.split('\n')[-1])
yt_dlp.postprocessor.ffmpeg.FFmpegPostProcessorError: file:/users/User/Downloads/tmp/NA/NA – Amateur hottie licking her best girlfriend's lovely toes in sixty-niner.unknown_video: Invalid data found when processing input
```