PC2-Sub (Predictable Closed Captions) Standard Draft

For Audio Description, please refer to standard PC2-AudioDesc. This standard is only for closed captions.

For Musical Lyrics, please refer to standard PC2-Lyrics.

• PC2-Subtitle Standard
• What is PC2?
• Aims of the PC2-Subtitle Standard
• Presumptions
• Good Practice Guidelines
• Media Type Descriptors
• Displaying Copyright & Other Notices
• PC2-Subtitle File Structure and Format
• Metadata Section
• Key Map Section

What is PC2?

The PC2 standard is a closed captioning standard created to make closed captions just better, by providing a standard and framework for both subtitle creators/editors and media playback systems to work from, making sure no matter where a piece of media is played, subtitles will look the same, and can be easily understood.

By providing an open set of rules and guides that anyone can contribute to, we can help make a closed captioning system that works for everyone.

Aims of the PC2-Subtitle Standard

• To provide a more predictable & standardised closed captioning system
• More specifically, how they are to be stored, how they  should be processed in editing, and how they should be displayed in a media viewer.
• Provide a standard file format and structure which allows for efficient storage of subtitles, and other relevant or additional metadata described within this standard
• Describe how a file should be created, edited and processed for display by both subtitle editing software and media playback systems.
• Provide additional metadata & information to a media playback system about a price of content, to allow a media playback system to gain additional context without requiring a internet connection.

Presumptions

• Media playback starts at 00:00:00:0000 exactly
• There are additional metadata flags that will indicate to a media player that this is not the case, and will provide a correct time stamp
• Media playback systems will be able to understand all parameters, metadata and other related items, described out in the PC2-Subtitle standard
• Any other data added, cannot be assumed to be compatible with a PC2-Subtitle media playback system

Good Practice Guidelines

Media Type Descriptors

A PC2-Subtitle file can describe its related media as one of the following types:

• TV Series Episode
• Movie
• Special/One Off
• Social Content
• e.g. a YouTube video

The provided “Additional Data Flags” provided by the standard should be used to classify what type of sub-media a piece of media or content is, rather then using a general media type where it is not needed

Examples are provided below:

Example 1
An upcoming TV show has released a trailer. It should have a media    descriptor of a TV Series Episode, should have series and episode left undefined, and should have the ADF (Additional Data Flag) of is is Trailer? set to True.

Example 2
A movie has released a behind the scenes video. It should have a media media of Movie, the title should be set to (Movie Name) - Behind the Scenes - or similar, depending on platform guidelines or what appears in a content selector), a ADF of Special added. A description text can be added of Behind the Scenes, however this is optional.

Displaying Copyright & Other Notices

A media playback system should (if available), display the relevant copyright info of the subtitle author at the timestamps provided within the metadata. It is assumed that these timestamps will be provided.

It is up to the author and/or the subtitle editing software to provide these timestamps. If none are available, the media playback system should display the copyright and contact information in the last 7 seconds of playback, unless there are already subtitles filling that space.

When specifying timestamps, they work backwards. So 00:00:20:0000 would mean the last 20 seconds of a media piece.

In this case, any remaining space should be used. If there is none, no copyright information should be displayed.

Additional Notes from Abi

PC2-Subtitle File Structure and Format

A PC2-Subtitle compliant file should be stored in a .pc2sub file.

The file structure is broken down into three key sections; the “metadata” section, the key map section, and the subtitle section.

This is for reference only. Actual file examples and structures can be found here

A PC2 compliant file is based of a YAML structure, so when editing in a text editor, if available, the syntax should be set to YAML to make sure the file conforms to the YAML format.

Metadata Section

This section contains metadata that can be used by a media playback system to provide additional info to a viewer, and also to respect the copyright of the subtitle author. Optional sections will be marked as such.

Subtitle Author Info

• Name/Psudoname
• Copyright information
• Timestamps
• Contact information

(Primary) Production Studios Info (Optional)

• Studio Name
• Studio Copyright information
• Studio Contact information

Production Info

• Content Name
• Content Release Date
• Writers

Additional Data Flags

• is Trailer?
• is Special?
• is Teaser?

TV Series Episode

• Series Info (Optional)
• Series Name
• Series No.
• Episode No.

Social Content

• Content Creator/Uploader (Optional)

Key Map Section

This section is mainly a setup for the subtitle section, this defines how each characters line should appear (e.g. what colour?, what is their name?, what is their id?). This does not provide a space to describe a character, however a separate PC2 standard may be created for this.

Only main characters should be assigned a custom key map. There is a separate key map for side characters that only appear for a short amount of time.

This will be replicated for each main character.

• Reference ID
• Hex Colour Code
• Character Name

Subtitle Section

This is where the bulk of the file will go, this lays out all of the subtitles for each character, throughout the duration of the full media piece.

Due to the way a subtitle line is formatted (from here will be called a SL), there is no structure layed out here at this time. This may change in the future. There will be example files below.

PC2-Subtitle Examples

Here are some provided examples of how a PC2-Subtitle compliant file should look and appear. These are provided as downloadable files due to their size. A small sample file can be found below, as well as download links.

GitHub Sample

- metadata:
    - length: “00:01:00:0000”
    - author:
        - name: Abigail Henderson
        - copyright: Copyright Abigail Henderson 2023
            - timestamps:
                - start: “00:00:09:5000”
                - end:   “00:00:00:0000”
        - contact:
            - email: abi@quickexit.cc
            - website: quickexit.cc
    - production:
        - name: GitHub Sample
        - release: 01/01/2023
        - writers: Abigail Henderson
    - mediaType: Special

- keymap:
    - 01:
        - name: Char 1
        - hexcode: 0000ff
    - 02:
        - name: Char 2
        - hexcode: ee44ff

- subtitles:
    -