Class: VideoProcessing::VideoTranslationService

Inherits:
Object
  • Object
show all
Defined in:
app/services/video_processing/video_translation_service.rb

Overview

Service to translate video captions and transcripts using AssemblyAI Speech Understanding API
Supports translation to Quebec French (fr-CA), Mexican Spanish (es-MX), and Polish (pl)

Uses native AssemblyAI translation for better quality and efficiency:

  • Single API call translates to all languages at once
  • Native utterance matching preserves timing
  • Falls back to LLM Gateway for individual caption translation if needed

Constant Summary collapse

SUPPORTED_LOCALES =

Supported target locales with AssemblyAI language codes

{
  'fr-CA' => { language: 'French', variant: 'Quebec French / Canadian French', name: 'Français', assemblyai_code: 'fr' },
  'es-MX' => { language: 'Spanish', variant: 'Mexican Spanish', name: 'Español', assemblyai_code: 'es' },
  'pl' => { language: 'Polish', variant: 'Standard Polish', name: 'Polski', assemblyai_code: 'pl' }
}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(video) ⇒ VideoTranslationService

Returns a new instance of VideoTranslationService.



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# File 'app/services/video_processing/video_translation_service.rb', line 21

def initialize(video)
  @video = video
end

Instance Attribute Details

#video ⇒ Object (readonly)

Returns the value of attribute video.



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# File 'app/services/video_processing/video_translation_service.rb', line 19

def video
  @video
end

Class Method Details

.available_translations(video) ⇒ Object

Get available translations for a video



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# File 'app/services/video_processing/video_translation_service.rb', line 76

def self.available_translations(video)
  return [] unless video.structured_transcript_json.present?

  translations = []
  SUPPORTED_LOCALES.each_key do |locale|
    vtt_key = "vtt_#{locale.underscore}"
    next unless video.structured_transcript_json[vtt_key].present?

    translations << {
      locale: locale,
      name: SUPPORTED_LOCALES[locale][:name],
      caption_count: video.structured_transcript_json[vtt_key].length
    }
  end

  translations
end

Instance Method Details

#translate_captions(locales = SUPPORTED_LOCALES.keys, &progress_callback) {|83, "Translating to #{valid_locales.length} languages..."| ... } ⇒ Hash

Translate VTT captions to specified locales using AssemblyAI LLM Gateway
Translates the POLISHED captions, preserving our terminology and grammatical fixes

Parameters:

  • locales (Array<String, Symbol>) (defaults to: SUPPORTED_LOCALES.keys) —

    Target locales (e.g., ['fr-CA', 'es-MX', 'pl'])

  • progress_callback (Proc) —

    Optional callback for progress updates

Yields:

  • (83, "Translating to #{valid_locales.length} languages...")

Returns:

  • (Hash) —

    Results for each locale



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# File 'app/services/video_processing/video_translation_service.rb', line 30

def translate_captions(locales = SUPPORTED_LOCALES.keys, &progress_callback)
  Rails.logger.debug("Translating captions", video_id: @video.id, locale_count: locales&.size)

  return { success: false, error: 'No polished VTT available' } unless @video.has_polished_vtt?

  # Filter to valid locales
  valid_locales = locales.map(&:to_s).select { |l| SUPPORTED_LOCALES.key?(l) }

  yield(83, "Translating to #{valid_locales.length} languages...") if progress_callback

  # Translate polished captions using LLM Gateway
  translate_polished_captions(valid_locales, &progress_callback)
end

#translate_transcript(locales = SUPPORTED_LOCALES.keys) ⇒ Hash

Translate plain transcript text to specified locales

Parameters:

  • locales (Array<String, Symbol>) (defaults to: SUPPORTED_LOCALES.keys) —

    Target locales

Returns:

  • (Hash) —

    Results for each locale



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# File 'app/services/video_processing/video_translation_service.rb', line 47

def translate_transcript(locales = SUPPORTED_LOCALES.keys)
  Rails.logger.debug("Translating transcript", video_id: @video.id, locale_count: locales&.size)

  return { success: false, error: 'No transcript available' } if @video.transcript.blank?

  results = {}
  locales.each do |locale|
    locale_str = locale.to_s
    next unless SUPPORTED_LOCALES.key?(locale_str)

    begin
      translated_text = translate_text(@video.transcript, locale_str)
      @video.send(:"transcript_#{locale_str.underscore}=", translated_text)
      results[locale_str] = { success: true, length: translated_text.length }
    rescue StandardError => e
      Rails.logger.error "Failed to translate transcript to #{locale_str}: #{e.message}"
      results[locale_str] = { success: false, error: e.message }
    end

    sleep(0.5) unless locale == locales.last
  end

  # Save the video with translated transcripts
  @video.save! if results.values.any? { |r| r[:success] }

  results
end