Extract video captions

Prerequisites

• An AccessKey pair is created and obtained. For more information, see Create an AccessKey pair.

• Object Storage Service (OSS) is activated and a bucket is created. For more information, see Create a bucket.

• IMM is activated. For more information, see Activate IMM.

• A project is created in the IMM console. For more information, see Create a project.

  Note

  • You can call the CreateProject operation to create a project. For more information, see CreateProject.

  • You can call the ListProjects operation to list information of all projects in a region.

Step 1: Upload a file

Upload your media file to an OSS bucket in the same region as your IMM project.

On the upload page, keep File ACL set to Inherit Bucket (default), click Scan File to select your file, then click Upload File.

Step 2: Extract captions

Call the CreateMediaConvertTask operation to create a video caption extraction task.

The extraction process includes these steps:

1. Format detection: Identify caption formats in the video file, such as SRT, ASS, WebVTT, and embedded subtitle streams.

2. Data extraction: Extract caption text and timestamps from the video file, including speaker names, time markers, and formatting.

3. Text processing: Edit the extracted captions as needed—remove redundant information, reformat, translate, or correct errors.

4. Output: Save the processed captions in a specified format (such as .srt or .ass) for later use or upload to a video platform.

Extract all captions from a video as WebVTT captions

• Caption format: webvtt

• Output caption file path: oss://test-bucket/video-demo/subtitle-%d.vtt

• Completion notification: MNS topic "test-mns-topic"

Try this example in OpenAPI Explorer with pre-filled parameters. Modify them as needed.

Request parameters

{
  "ProjectName": "test-project",
  "Notification": {
    "MNS": {
      "TopicName": "test-mns-topic"
    }
  },
  "Sources": [
    {
      "URI": "oss://test-bucket/video-demo/test.mp4"
    }
  ],
  "Targets": [
    {
      "Subtitle": {
        "ExtractSubtitle": {
          "Format": "webvtt",
          "URI": "oss://test-bucket/video-demo/subtitle-{streamindex}.{autoext}"
        }
      }
    }
  ]
}

Extract all captions from a video as SRT captions

• Caption format: srt

• Output caption file path: oss://test-bucket/video-demo/subtitle-%d.srt

• Completion notification: MNS topic "test-mns-topic"

Try this example in OpenAPI Explorer with pre-filled parameters. Modify them as needed.

Request parameters

{
  "ProjectName": "test-project",
  "Notification": {
    "MNS": {
      "TopicName": "test-mns-topic"
    }
  },
  "Sources": [
    {
      "URI": "oss://test-bucket/video-demo/test.mp4"
    }
  ],
  "Targets": [
    {
      "Subtitle": {
        "ExtractSubtitle": {
          "Format": "srt",
          "URI": "oss://test-bucket/video-demo/subtitle-{streamindex}.{autoext}"
        }
      }
    }
  ]
}