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AI Subtitle

Notice

This document is a machine-translated draft and is currently undergoing review. Some content may be inaccurate or differ from the original Korean version. For the most precise information, please refer to the Korean documentation.

AI Subtitle is an innovative feature that uses advanced AI-based Speech-to-Text(STT) technology to analyze speech data within content in real time and automatically convert it into subtitle files.

Key benefits of AI Subtitle​

AI Subtitle significantly reduces the time and cost of manual subtitle production, allowing you to quickly introduce subtitle services to large video libraries.

  • Cost and time savings: AI analyzes audio to generate subtitles, dramatically reducing production time.
  • Precise automatic sync: The system automatically detects the start and end points of speech to determine subtitle timestamps, eliminating the need for manual sync work.
  • Enhanced operational efficiency: Subtitles can be instantly applied to large VOD libraries, boosting global service competitiveness.
  • Easy post-editing: Automatically generated subtitles can be immediately corrected and supplemented through the subtitle editor.

Generate AI Subtitle​

Pre-checklist

AI Subtitle can only be generated for content that meets all of the following technical conditions.

  • Security policy: Content without Multi DRM applied
    • AI Subtitle generation is available for standard content(unencrypted) and Kollus DRM content.
  • Audio quality: Content where the audio sample rate of the transcoded file is 16kHz or higher
  • Duplicate generation prevention: A maximum of 1 AI Subtitle can be generated per content. If an AI Subtitle already exists, you can delete it and regenerate.

Automatic generation when uploading new content​

If you enable the AI Subtitle option during the content upload step, subtitles will be automatically generated after transcoding is complete.

  1. In the Kollus VOD console > [Library] menu, click [Content upload] in the upper right corner.
  2. Select [Generate AI subtitle] from the upload options.
  3. After completing the subtitle settings, click [Confirm].
    ItemDescription
    LanguageSelect the language to be used as the basis for speech analysis. Currently supports Korean(KO) and English(EN).
    Subtitle type
    • Main subtitle: Used for delivering main dialogue, displayed at standard size at the bottom of the player.
    • Sub subtitle: An auxiliary subtitle displayed in smaller size below the main subtitle.
    Subtitle visibilitySelect whether to make the subtitle public.
    • Public (default): Displayed in the player's subtitle menu so users can select it.
    • Private: Saved on the server but not displayed in the player.
  4. Drag and drop files into the upload area or click [Select file] to select the content to upload.
  5. Once uploading and transcoding are complete, the system will automatically generate subtitles.
  6. When generation is complete, an 'AI Subtitle' tag will be displayed below the title.
Tip

AI Subtitle can also be automatically generated via the FTP upload method using folder naming conventions.

Generate for existing content​

AI Subtitle can also be generated for content that has already been uploaded.

Method 1: Generate from the content list​

  1. In Kollus VOD console > [Library] or [Channel], select the checkbox to the left of the target content.
  2. In the bottom toolbar, click [Generate AI subtitle] > [Generate AI subtitle].
  3. After completing the subtitle settings, click [Confirm].
    ItemDescription
    LanguageSelect the language to be used as the basis for speech analysis.
    Subtitle type
    • Main subtitle: Used for delivering main dialogue, displayed at standard size at the bottom of the player.
    • Sub subtitle: An auxiliary subtitle displayed in smaller size below the main subtitle.
    Subtitle visibilitySelect whether to make the subtitle public.
    • Public (default): Displayed in the player's subtitle menu so users can select it.
    • Private: Saved on the server but not displayed in the player.
  4. For content where AI Subtitle generation is complete, an 'AI Subtitle' tag will be displayed below the title.

Method 2: Generate from the [Subtitle] tab​

  1. In Kollus VOD console > [Library] or [Channel], click [More options (⋮)] > [Subtitle] to the right of the target content.
  2. In the [Subtitle] tab, click [Generate AI subtitle].
  3. After completing the subtitle settings, click [Confirm].
    ItemDescription
    LanguageSelect the language to be used as the basis for speech analysis.
    Subtitle type
    • Main subtitle: Used for delivering main dialogue, displayed at standard size at the bottom of the player.
    • Sub subtitle: An auxiliary subtitle displayed in smaller size below the main subtitle.
    Subtitle visibilitySelect whether to make the subtitle public.
    • Public (default): Displayed in the player's subtitle menu so users can select it.
    • Private: Saved on the server but not displayed in the player.
  4. When AI Subtitle generation is complete, '(AI) Auto-generated subtitle' will be added to the list.

Edit AI Subtitle​

Editing AI Subtitle text follows the same method as editing regular subtitles. Refer to the document below for detailed instructions.

Modify AI Subtitle settings​

  1. In Kollus VOD console > [Library] or [Channel], click the title of the target content.
  2. In the [Subtitle] tab, click [More options (⋮)] > [Edit subject and language] to the right of the subtitle file.
  3. The following items can be modified.
    ItemDescription
    Subtitle nameThe name displayed in the subtitle selection menu of the player.
    Subtitle type
    • Main subtitle: Used for delivering main dialogue, displayed at standard size at the bottom of the player.
    • Sub subtitle: An auxiliary subtitle displayed in smaller size below the main subtitle.
  4. After completing modifications, click [Edit].

Set subtitle to private​

To hide subtitles from the user's screen without deleting them, use the toggle switch on the right side of the list to switch to the private state. (Same as the regular subtitle setting)

Subtitle public state

Subtitle private state

Download AI Subtitle file​

Generated AI Subtitles can be downloaded in the widely compatible SRT format, and all the latest edits at the time of download will be reflected.

  1. In Kollus VOD console > [Library] or [Channel], click the title of the target content.
  2. In the [Subtitle] tab, click [More options (⋮)] > [SRT download] to the right of the subtitle file.

AI Subtitle display policy​

  • Subtitle display priority: If a content has both a manually uploaded regular subtitle by an administrator and a system-generated AI Subtitle, the regular subtitle, which is verified data, will be activated with higher priority.
  • AI Subtitle notice message: When a user activates AI Subtitle, a notice indicating that the information was automatically generated by artificial intelligence will be displayed for approximately 3 seconds.

    Kollus HTML5 Player


    Kollus App Player (iOS/Android)

FAQ​

Q. What content can AI Subtitle be generated for?​

AI Subtitle can only be generated for content that meets all of the following technical conditions.

  • Security policy: Content without Multi DRM applied (Kollus DRM is supported)
  • Audio quality: Content where the audio sample rate of the transcoded file is 16kHz or higher
  • Duplicate generation prevention: A maximum of 1 AI Subtitle can be generated per content. If an AI Subtitle already exists, you can delete it and regenerate.

Q. Is there a limit on content length?​

Yes, for stable data processing, there are limits on the content length that can be generated per language.

  • Korean content: Maximum 11 hours
  • English content: Minimum 30 seconds ~ Maximum 2 hours Very short or very long content that falls outside these limits may encounter Timeout errors or failures during processing. Therefore, it is recommended to split long-form videos into appropriate segments for smooth subtitle generation.

Q. Can AI Subtitle be generated for audio-only content?​

Yes. AI Subtitle can be generated by analyzing voice data from audio-only content without video (e.g., MP3).

Q. Can subtitles be generated for DRM content?​

It depends on the security method.

  • Kollus DRM: AI Subtitle generation is available.
  • Multi DRM: Due to the strong security specifications of the content itself, audio extraction is blocked, making AI Subtitle generation unavailable.

Q. How long does it take to complete AI Subtitle generation?​

Generally, it takes approximately 10 minutes for a 60-minute video. (This may vary depending on system load.)

Q. Can an in-progress job be cancelled?​

No. Once AI Subtitle generation starts, system resources are immediately allocated, so it cannot be cancelled midway. Please make sure to verify the settings (language, type, etc.) before initiating generation.

Q. Why is the speech recognition accuracy lower than expected?​

Due to the characteristics of the STT(Speech-to-Text) engine, misrecognition is more likely to occur in the following environments.

  • When background noise or music(BGM) is louder than the speech
  • When the speaker's pronunciation is unclear
  • When multiple speakers' voices overlap For sections with low accuracy, manual editing through the subtitle editor is recommended.