# Deepgram Common Errors - Implementation Details

## Audio File Validation

```typescript
import { readFileSync, statSync } from 'fs';

function validateAudioFile(filePath: string): boolean {
  const stats = statSync(filePath);
  if (stats.size < 100 || stats.size > 2 * 1024 * 1024 * 1024) {
    console.error('Invalid file size');
    return false;
  }

  const buffer = readFileSync(filePath, { length: 12 });
  const header = buffer.toString('hex', 0, 4);
  const validHeaders = {
    '52494646': 'WAV',
    'fff3': 'MP3',
    'fff2': 'MP3',
    'fffb': 'MP3',
    '664c6143': 'FLAC',
    '4f676753': 'OGG',
  };

  return Object.keys(validHeaders).some(h => header.startsWith(h));
}
```

## Large File Splitting

```typescript
import { exec } from 'child_process';
import { promisify } from 'util';

const execAsync = promisify(exec);

async function splitAudio(inputPath: string, chunkDuration: number = 300) {
  const outputPattern = inputPath.replace('.wav', '_chunk_%03d.wav');
  await execAsync(
    `ffmpeg -i ${inputPath} -f segment -segment_time ${chunkDuration} -c copy ${outputPattern}`
  );
}
```

## Rate Limiter Implementation

```typescript
class RateLimiter {
  private queue: Array<() => Promise<void>> = [];
  private processing = false;
  private lastRequest = 0;
  private minInterval = 100;

  async add<T>(fn: () => Promise<T>): Promise<T> {
    return new Promise((resolve, reject) => {
      this.queue.push(async () => {
        const now = Date.now();
        const elapsed = now - this.lastRequest;
        if (elapsed < this.minInterval) {
          await new Promise(r => setTimeout(r, this.minInterval - elapsed));
        }
        try {
          this.lastRequest = Date.now();
          resolve(await fn());
        } catch (error) {
          reject(error);
        }
      });
      this.process();
    });
  }

  private async process() {
    if (this.processing) return;
    this.processing = true;
    while (this.queue.length > 0) {
      const fn = this.queue.shift()!;
      await fn();
    }
    this.processing = false;
  }
}
```

## WebSocket Connectivity Test

```typescript
async function testWebSocketConnection() {
  const ws = new WebSocket('wss://api.deepgram.com/v1/listen', {
    headers: { Authorization: `Token ${process.env.DEEPGRAM_API_KEY}` },
  });

  return new Promise((resolve, reject) => {
    ws.onopen = () => { console.log('WebSocket connected'); ws.close(); resolve(true); };
    ws.onerror = (error) => { console.error('WebSocket error:', error); reject(error); };
    setTimeout(() => reject(new Error('Connection timeout')), 10000);
  });
}
```

## Keep-Alive Implementation

```typescript
class DeepgramWebSocket {
  private keepAliveInterval: NodeJS.Timeout | null = null;

  start() {
    this.keepAliveInterval = setInterval(() => {
      if (this.connection?.readyState === WebSocket.OPEN) {
        this.connection.send(JSON.stringify({ type: 'KeepAlive' }));
      }
    }, 10000);
  }

  stop() {
    if (this.keepAliveInterval) clearInterval(this.keepAliveInterval);
  }
}
```

## Debug Transcription

```typescript
async function debugTranscription(audioPath: string) {
  const client = createClient(process.env.DEEPGRAM_API_KEY!);
  const { result, error } = await client.listen.prerecorded.transcribeFile(
    readFileSync(audioPath),
    { model: 'nova-2', smart_format: true, alternatives: 3, words: true, utterances: true }
  );

  if (error) { console.error('Error:', error); return; }

  const alt = result.results.channels[0].alternatives[0];
  console.log('Confidence:', alt.confidence);
  console.log('Word count:', alt.words?.length);
  console.log('Low confidence words:', alt.words?.filter(w => w.confidence < 0.7));
}
```

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