Disc Images: ISO Files
A disc image stores a volume and its filesystem as a file, preserving a disc presentation rather than replacing it with a single encoded movie.
Mount an ISO image and a file browser can show a disc's folders. The operation interprets a stored volume; it has not yet selected a movie, separated its tracks, or decoded its pictures.
A conventional .iso image commonly stores the logical data sectors of a disc as one file. The extension does not guarantee that the contained filesystem is ISO 9660: UDF or a bridge arrangement can also be present.
Sectors, files, playlists, and encoded media
| Layer | Reader operation |
|---|---|
| Image and volume | Obtain logical sectors and recognize the filesystem |
| Filesystem | Resolve names such as VIDEO_TS or BDMV into file locations |
| Disc presentation | Select a title, playlist, branches, and media ranges |
| Media containers | Read VOB or M2TS timing and encoded components |
| Codecs | Reconstruct the chosen picture and sound |
Each layer supplies information to the next. A volume can mount successfully while a particular contained file is damaged. A media stream can decode successfully while an incorrect playlist produces the wrong feature.
What preserving an image retains
Keeping the volume can retain directory structure, menus, extras, several cuts, and relationships between files. It preserves a disc-shaped source rather than merely one movie's selected tracks.
A filesystem can describe a file through sector locations or extents. The image reader resolves those locations when another reader requests the named file. Copying an individual M2TS or VOB removes that outer filesystem context but still leaves the disc presentation choices to consider.
A feature remux goes further: it follows the intended DVD title or Blu-ray playlist, obtains selected media, and writes a new linear container. Its output can preserve the encoded feature while omitting menus and extras. The difference is a selected presentation, not simply a different spelling of the same image.
Access and protection remain at their boundaries
Mounting supplies a way to access stored bytes. It does not authorize decryption of protected media. A disc-aware playback path and an ordinary movie-file reader also perform different jobs; a decoder accepting the underlying codec does not supply the filesystem and navigation stages by itself.
For an Emby library, identify and organize the actual source form. If an image reports the wrong title or duration, inspect the contained disc structure and selected presentation before judging codec conversion.
An image's completeness is tested by its content and readability, not by a successful mount alone. This layered view places a missing file, wrong playlist, damaged stream, or unavailable decoder at the stage that actually failed.