Creating video subtitles - Amazon Transcribe
Generating subtitle files

Creating video subtitles

Amazon Transcribe supports WebVTT (*.vtt) and SubRip (*.srt) output for use as video subtitles. You can select one or both file types when setting up your batch video transcription job. When using the subtitle feature, your selected subtitle file(s) and a regular transcript file (containing additional information) are produced. Subtitle and transcription files are output to the same destination.

Subtitles are displayed at the same time text is spoken, and remain visible until there is a natural pause or the speaker finishes talking. Note that if you enable subtitles in your transcription request and your audio contains no speech, a subtitle file is not created.

Important

Amazon Transcribe uses a default start index of 0 for subtitle output, which differs from the more widely used value of 1. If you require a start index of 1, you can specify this in the AWS Management Console or in your API request using the OutputStartIndex parameter.

Using the incorrect start index can result in compatibility errors with other services, so be sure to verify which start index you require before creating your subtitles. If you're uncertain which value to use, we recommend choosing 1. Refer to Subtitles for more information.

Features supported with subtitles:

  • Content redaction — Any redacted content is reflected as 'PII' in both your subtitle and regular transcript output files. The audio is not altered.

  • Vocabulary filters — Subtitle files are generated from the transcription file, so any words you filter in your standard transcription output are also filtered in your subtitles. Filtered content is displayed as whitespace or *** in your transcript and subtitle files. The audio is not altered.

  • Speaker diarization — If there are multiple speakers in a given subtitle segment, dashes are used to distinguish each speaker. This applies to both WebVTT and SubRip formats; for example:

    • -- Text spoken by Person 1

    • -- Text spoken by Person 2

Subtitle files are stored in the same Amazon S3 location as your transcription output.

For a video walkthrough of creating subtitles, see:

Generating subtitle files

You can create subtitle files using the AWS Management Console, AWS CLI, or AWS SDKs; see the following examples:

  1. Sign in to the AWS Management Console.

  2. In the navigation pane, choose Transcription jobs, then select Create job (top right). This opens the Specify job details page. Subtitle options are located in the Output data panel.

  3. Select the formats you want for your subtitles files, then choose a value for your start index. Note that the Amazon Transcribe default is 0, but 1 is more widely used. If you're uncertain which value to use, we recommend choosing 1, as this may improve compatibility with other services.

    Amazon Transcribe console screenshot: the 'output data' pane on the 'specify job details' page.

  4. Fill in any other fields you want to include on the Specify job details page, then select Next. This takes you to the Configure job - optional page.

  5. Select Create job to run your transcription job.

This example uses the start-transcription-job command and Subtitles parameter. For more information, see StartTranscriptionJob and Subtitles.

aws transcribe start-transcription-job \
--region us-west-2 \
--transcription-job-name my-first-transcription-job \
--media MediaFileUri=s3://DOC-EXAMPLE-BUCKET/my-input-files/my-media-file.flac \
--output-bucket-name DOC-EXAMPLE-BUCKET \
--output-key my-output-files/ \
--language-code en-US \
--subtitles Formats=vtt,srt,OutputStartIndex=1

Here's another example using the start-transcription-job command, and a request body that adds subtitles to that job.

aws transcribe start-transcription-job \
--region us-west-2 \
--cli-input-json file://my-first-subtitle-job.json

The file my-first-subtitle-job.json contains the following request body.

{
  "TranscriptionJobName": "my-first-transcription-job",
  "Media": {
        "MediaFileUri": "s3://DOC-EXAMPLE-BUCKET/my-input-files/my-media-file.flac"
  },
  "OutputBucketName": "DOC-EXAMPLE-BUCKET",
  "OutputKey": "my-output-files/", 
  "LanguageCode": "en-US",
  "Subtitles": {
        "Formats": [
            "vtt","srt"
        ],             
        "OutputStartIndex": 1
   }
}

This example uses the AWS SDK for Python (Boto3) to add subtitles using the Subtitles argument for the start_transcription_job method. For more information, see StartTranscriptionJob and Subtitles.

For additional examples using the AWS SDKs, including feature-specific, scenario, and cross-service examples, refer to the Code examples for Amazon Transcribe using AWS SDKs chapter.

from __future__ import print_function
import time
import boto3
transcribe = boto3.client('transcribe', 'us-west-2')
job_name = "my-first-transcription-job"
job_uri = "s3://DOC-EXAMPLE-BUCKET/my-input-files/my-media-file.flac"
transcribe.start_transcription_job(
    TranscriptionJobName = job_name,
    Media = {
        'MediaFileUri': job_uri
    },
    OutputBucketName = 'DOC-EXAMPLE-BUCKET',
    OutputKey = 'my-output-files/', 
    LanguageCode = 'en-US', 
    Subtitles = {
        'Formats': [
            'vtt','srt'
        ],
        'OutputStartIndex': 1 
   }
)

while True:
    status = transcribe.get_transcription_job(TranscriptionJobName = job_name)
    if status['TranscriptionJob']['TranscriptionJobStatus'] in ['COMPLETED', 'FAILED']:
        break
    print("Not ready yet...")
    time.sleep(5)
print(status)