update Manual Media Files Import docs

docs/Settings.md

@@ -116,25 +116,32 @@ Additional database functionality.
 The button **Delete all queued** will delete all pending videos from the download queue. The button **Delete all ignored** will delete all videos you have previously ignored.
 
 ## Manual Media Files Import
-So far this depends on the video you are trying to import to be still available on YouTube to get the metadata. Add the files you'd like to import to the */cache/import* folder. Then start the process from the settings page *Manual Media Files Import*. Make sure to follow one of the two methods below.
+Add the files you'd like to import to the */cache/import* folder. Only add files, don't add subdirectories. All files you are adding, need to have the same *base name* as the media file. Then start the process from the settings page *Manual Media Files Import*.
+
+Valid media extensions are *.mp4*, *.mkv* or *.webm*. If you have other file extensions or incompatible codecs, convert them first to mp4. **Tube Archivist** can identify the videos with one of the following methods.
 
 ### Method 1:
-Add a matching *.json* file with the media file. Both files need to have the same base name, for example:
-- For the media file: \<base-name>.mp4
-- For the JSON file: \<base-name>.info.json
-- Alternate JSON file: \<base-name>.json
+Add a matching *.info.json* file with the media file. Both files need to have the same base name, for example:
+- For the media file: `<base-name>.mp4`
+- For the JSON file: `<base-name>.info.json`
 
-**Tube Archivist** then looks for the 'id' key within the JSON file to identify the video.
+The import process then looks for the 'id' key within the JSON file to identify the video.
 
 ### Method 2:
 Detect the YouTube ID from filename, this accepts the default yt-dlp naming convention for file names like:
-- \<base-name>[\<youtube-id>].mp4
+- `<base-name>[<youtube-id>].mp4`
 - The YouTube ID in square brackets at the end of the filename is the crucial part.
 
+### Offline import:
+If the video you are trying to import is not available on YouTube any more, **Tube Archivist** can import the required metadata:
+- The file `<base-name>.info.json` is required to extract the required information.
+- Add the thumbnail as `<base-name>.<ext>`, where valid file extensions are *.jpg*, *.png* or *.webp*. If there is no thumbnail file, **Tube Archivist** will try to extract it from the media file or will fallback to a default thumbnail.
+- Add subtitles as `<base-name>.<lang>.vtt` where *lang* is the two letter ISO country code. This will archive all subtitle files you add to the import folder, independent from your configurations. Subtitles can be archived and used in the player, but they can't be indexed or made searchable due to the fact, that they have a very different structure than the subtitles as **Tube Archivist** needs them.
+- For videos, where the whole channel is not available any more, you can add the `<channel-id>.info.json` file as generated by *youtube-dl/yt-dlp* to get the full metadata. Alternatively **Tube Archivist** will extract as much info as possible from the video info.json file. 
+
 ### Some notes:
 - This will **consume** the files you put into the import folder: Files will get converted to mp4 if needed (this might take a long time...) and moved to the archive, *.json* files will get deleted upon completion to avoid having duplicates on the next run.
-- For best file transcoding quality, convert your media files with desired settings first before importing (#138).
-- There should be no subdirectories added to */cache/import*, only video files. If your existing video library has video files inside subdirectories, you can get all the files into one directory by running `find ./ -mindepth 2 -type f -exec mv '{}' . \;` from the top-level directory of your existing video library. You can also delete any remaining empty subdirectories with `find ./ -mindepth 1 -type d -delete`.
+- For best file transcoding quality, convert your media files with desired settings first before importing.
 - Maybe start with a subset of your files to import to make sure everything goes well...
 - Follow the logs to monitor progress and errors: `docker-compose logs -f tubearchivist`.