Captions vs Subtitles: Main differences

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Caption formats: SRT and WebVTT

So, when we are dealing with captions, we’ve got a bunch of formats to choose from. But two of them stand out: SRT and WebVTT.

The first and the most widely used is SRT (SubRip Subtitle). SRT is like the old reliable friend of subtitle formats. It's super simple – just a plain text file with the words and when they should appear on the screen. That's why so many video editors and content creators love it. It's perfect if you're just starting or need something quick and easy.

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Here’s an example of an SRT file:

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362

00:20:01.809 -> 00:20:03.149

You either die a hero...

363

00:20:03.249 -> 00:20:04.549

...or you live long enough...

364
00:20:04.649 -> 00:20:06.229

to see yourself become the villain.

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SRT excels at its primary function. However, if you're looking for fancy formatting options, you might find it somewhat limited. It's great at handling basic subtitle needs yet falls short when more advanced features are required.

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WebVTT (Web Video Text Tracks) is a more advanced subtitle format compared to SRT. It handles basic subtitle functions and offers additional features such as styling, positioning, and metadata support. WebVTT is particularly useful for projects requiring more than simple text subtitles, providing enhanced functionality for web-based video content.

Here’s an example of a WebVTT file. All WebVTT files start with the WEBVTT header to indicate the file format.

WEBVTT

11

00:05:10.000 -> 00:05:12.500

Bruce Wayne: I've had training!

12

00:05:13.000 -> 00:05:16.000

Henri Ducard: The training is nothing! The will is everything!

13

00:05:16.500 --> 00:05:19.000

Henri Ducard: The will to act.

WebVTT is an official W3C (World Wide Web Consortium) standard specifically designed for HTML5 video, ensuring better compatibility and support across modern web browsers compared to the more basic SRT format. It's built for the video world we're living in now.

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Subtitles and captions with FastPix

Here at FastPix, we use the Common Media Application Format (CMAF) to stream all our video content. While the CMAF protocol supports a variety of captioning formats, we believe WebVTT is the best alternative.

When you import captions into FastPix, you must provide a valid WebVTT file. You can choose to provide this file as input or have captions generated automatically by OpenAI’s Whisper model.

If you want to try adding some captions to your video, follow our documentation and steps to get started guide. You will learn about the prerequisites and get an introduction to using FastPix APIs, ensuring you have all the necessary information to successfully integrate captions into your videos.

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Method 1: Creating media from URL‍

1. Prepare the video URL and metadata like type, start, end, language code, etc.
2. Send a POST request to the ‘/media/’ endpoint with the following JSON payload:

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{ 
 "inputs": [ 
    { 
      "type": "video", 
      "url": "https://storage.googleapis.com/gtv-videos-bucket/sample/ForBiggerJoyrides.mp4", 
      "startTime": 0, 
      "endTime": 60 
    }, 

 "createSubtitles": { 
    "name": "name", 
    "metadata": { 
      "key1": "value1" 
    }, 
    "languageCode": "en-us" 
  },

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1. Replace https://storage.googleapis.com/gtv-videos-bucket/sample/ForBiggerJoyrides.mp4 with your video URL.
2. After processing the request, a new media asset will be created with the subtitles added automatically.
3. The response will include the ID of the created media file, which you can use for further actions.

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Method 2: Adding subtitle file manually

1. Prepare the ID of the existing media you want to add subtitles to, and the URL of the subtitles track to be added.
2. Send a POST request to the ‘/media/{mediaId}/tracks’ endpoint with the following JSON payload:

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{ 
  "url": "https://storage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.vtt",
  "type": "subtitle", 
  "languageCode": "en-US", 
  "languageName": "english", 
  "metadata": { 
    "key1": "value1" 
  }, 
  "closedCaptions": false 
}

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1. Replace https://storage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.vtt with the URL of your subtitle file in VTT format.
2. After processing the request, the subtitle track is added to the media asset.
3. The response will confirm the successful addition of the track.

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Method 3: Uploading video file directly from your device

1. Prepare the video file you want to upload and add subtitles to.
2. Send a POST request to the ‘/uploads’ endpoint with the following JSON payload:

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{ 
  "corsOrigin": "*", 
  "pushMediaSettings": { 
    "accessPolicy": "private", 
    "startTime": 0, 
    "endTime": 60, 
    "createSubtitles": { 
      "name": "name", 
      "metadata": { 
        "key1": "value1" 
      }, 
      "languageCode": "en-us" 
    }, 
    "optimizeAudio": true, 
    "maxResolution": "1080p" 
  } 
}

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1. Upon sending the request, you will receive a response indicating whether the media creation was successful.
2. The response will include details such as the media ID, status, and media URL.

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Review the response

• 201 Created response indicates that the media was successfully created.
• 400 Bad Request response means there was an issue with the request format or data.
• 401 Unauthorized response indicates that your credentials are invalid.
• 402 Payment Required response suggests that your account may need to be upgraded or that you have exceeded your usage limits.

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By following these steps, you can successfully create media with subtitles using the FastPix API. Remember to adjust the values in the JSON payload as necessary to fit your specific requirements.

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Accessibility and formatting guidelines

According to the 2014 mandates by the Federal Communications Commission, for captions to be high quality, they need to be:

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Accurate - This means there should be no errors or mistakes. The industry standard is 99% accuracy. Always review your captions and subtitles, even if you think they are perfect. Do not correct incorrect grammar in the speaker’s dialogue.

Consistent - Your captions should maintain uniform features throughout the content. Avoid changing fonts or colors unless they have a specific purpose, such as differentiating between speakers.

Clear - Captions should clearly indicate who is speaking and convey any non-verbal information, such as sound effects or music cues. Their primary purpose is to enhance comprehension and ensure the content remains accessible, even when the audio is muted.

Readable - Choose an appropriate font and sync captions with the audio properly. Ensure captions stay on screen long enough for viewers to read them comfortably.

Equal - Captions should accurately convey the meaning and intent of the spoken content.

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Caption Font Styles Adopted by Major Streamers

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Style guide

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1. Font: Use a clear, sans-serif font like Arial or Helvetica for your captions. Ensure that the text is large enough to be easily readable, usually around 1/25th of the screen height, and the font size is consistent.

2. Color and contrast: Use high-contrast colors for clear visibility, like white text on a black background. You can consider providing customizable color options for your audience.

3. Speaker-oriented placement: Position captions near the speaker when multiple people are talking to help viewers identify who is speaking. Align captions to the left, right, or centre of the screen based on the speaker’s location.

3. Line length and duration: Limit each line of text to 32-42 characters to ensure readability. Display a maximum of two lines of text to avoid clutter. Allow a minimum of 0.3 seconds per word or 1.5 seconds per line to give viewers enough time to read the captions.

4. Positioning: By default, place captions at the bottom center of the screen. Be careful not to cover visual elements or on-screen text by maintaining consistent positioning throughout the video.

5. Timing and synchronization: Synchronize captions with the audio to ensure they appear at the right moment. Captions should match the corresponding audio and remain on screen long enough for viewers to read comfortably.

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Summing it up…

Using captions helps ensure everyone can enjoy your content, whether they’re dealing with a language barrier or a hearing impairment. At FastPix, we make it easy for content creators and businesses to enhance their videos with captions using our advanced AI-powered tools.

With FastPix, you can automatically generate subtitles in multiple languages, create closed captions that comply with ADA standards with features like speaker identification and sound descriptions, and effortlessly integrate these into your video workflow.

Try FastPix for free today and see how you can create great video experiences.