Court Recording Transcriber Development Guide

An AI-powered application for transcribing court recordings with speaker identification, synchronized playback, search functionality, and professional legal document exports.

Live site: https://court-record-transcriber.casedev.app

Architecture

src/
├── app/
│   ├── api/recordings/         # API routes for recordings
│   │   ├── route.ts            # List, create recordings
│   │   └── [id]/
│   │       ├── route.ts        # Get, update, delete
│   │       ├── transcribe/     # Start transcription
│   │       └── export/         # Export endpoints
│   ├── upload/                 # Upload page
│   └── recording/[id]/         # Transcript viewer page
├── components/
│   ├── ui/                     # shadcn/ui components
│   ├── AudioPlayer.tsx         # Waveform + playback
│   ├── TranscriptView.tsx      # Transcript display
│   ├── SpeakerEditor.tsx       # Label speakers
│   └── ExportDialog.tsx        # Export options
└── lib/
    ├── db/
    │   ├── index.ts            # Database connection
    │   └── schema.ts           # Drizzle schema
    ├── casedev/                # Case.dev API client
    └── legal-vocabulary.ts     # Word boosting config

Core Workflow

Upload Audio → Transcribe → Identify Speakers → Review/Edit → Export
     ↓             ↓              ↓                ↓            ↓
  MP3/WAV     Case.dev API    Auto-detect      Sync playback   PDF/Word/
  M4A/etc     with legal      Judge, Atty,    click-to-seek   Plain text
              vocabulary      Witness, etc

Tech Stack

| Layer | Technology | |-------|-----------| | Frontend | Next.js 16, React 19, Tailwind CSS | | Backend | Next.js API Routes | | Database | PostgreSQL + Drizzle ORM | | Audio | wavesurfer.js | | Transcription | Case.dev Speech-to-Text API | | Export | React PDF, docx library |

Key Features

| Feature | Description | |---------|-------------| | Audio Upload | Drag-drop MP3, WAV, M4A, FLAC, OGG | | AI Transcription | Case.dev API with legal vocabulary boosting | | Speaker ID | Auto-detect speakers, customizable labels | | Synced Playback | Click transcript line to jump to timestamp | | Search | Find words/phrases with highlighting | | Export | PDF, Word (.docx), plain text with legal formatting |

Database Operations

PostgreSQL with Drizzle ORM. See references/database-schema.md.

Commands

npm run db:push      # Push schema (dev)
npm run db:generate  # Generate migrations
npm run db:studio    # Open Drizzle Studio

Core Tables

recordings: id, filename, duration, status, audioUrl
transcripts: id, recordingId, content (JSON), speakerMap
utterances: id, transcriptId, speaker, text, startTime, endTime

Case.dev Integration

See references/casedev-transcription-api.md for API patterns.

Transcription Flow

// 1. Upload audio to Case.dev
const { audioId } = await uploadAudio(file);

// 2. Start transcription with legal vocabulary
const { jobId } = await startTranscription(audioId, {
  vocabulary: legalVocabulary,
  speakerDiarization: true,
});

// 3. Poll for completion
const transcript = await pollTranscriptionStatus(jobId);

// 4. Store results
await saveTranscript(recordingId, transcript);

Audio Playback

See references/audio-playback.md for wavesurfer.js patterns.

Key Features

Waveform visualization
Click-to-seek from transcript
Playback speed control
Keyboard shortcuts (space, arrows)

Development

Setup

npm install
cp .env.example .env.local
# Add CASEDEV_API_KEY and DATABASE_URL
npm run db:push
npm run dev

Environment

CASEDEV_API_KEY=sk_case_...       # Case.dev API key
DATABASE_URL=postgresql://...     # PostgreSQL connection
NEXT_PUBLIC_APP_URL=http://localhost:3000

Common Tasks

Adding a New Export Format

Create export function in lib/export/
Add endpoint in app/api/recordings/[id]/export/
Add option to ExportDialog.tsx

Customizing Speaker Labels

// Default labels
const speakerLabels = ['Judge', 'Plaintiff Attorney', 'Defense Attorney', 
                       'Witness', 'Clerk', 'Unknown'];

// In SpeakerEditor component, allow custom labels

Adding Legal Vocabulary

// lib/legal-vocabulary.ts
export const legalVocabulary = [
  'objection', 'sustained', 'overruled', 'plaintiff', 'defendant',
  'voir dire', 'habeas corpus', 'pro bono', 'amicus curiae',
  // Add more terms
];

Export Formats

| Format | Use Case | |--------|----------| | PDF | Official court filing, archive | | Word (.docx) | Editing, annotations | | Plain Text | Processing, search indexing | | SRT | Subtitles for video recordings |

Troubleshooting

| Issue | Solution | |-------|----------| | Transcription stuck | Check Case.dev API status, verify audio format | | Audio won't play | Verify audio URL accessible, check CORS | | Speaker labels wrong | Use SpeakerEditor to reassign | | Export fails | Check transcript exists, verify format support | | Waveform not showing | Ensure wavesurfer.js loaded, check audio src |