elevenlabs plugin

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Project	Deployment	Preview	Comments	Updated (UTC)
workflow-builder	Ready	Preview	Comment	Dec 2, 2025 9:04am

[vercel]

Suggested change

	const contentType = outputFormat.startsWith("mp3") ? "audio/mpeg" : "audio/wav";
	let contentType: string;
	if (outputFormat.startsWith("mp3")) {
	contentType = "audio/mpeg";
	} else if (outputFormat.startsWith("pcm")) {
	contentType = "audio/L16";
	} else {
	contentType = "audio/mpeg"; // fallback
	}

The content type mapping for audio formats is incorrect. PCM formats (pcm_16000, pcm_22050, pcm_24000, pcm_44100) are being labeled as "audio/wav" when they should use a different MIME type like "audio/L16" or "audio/x-raw".

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Analysis

Incorrect MIME type mapping for ElevenLabs PCM audio formats

What fails: textToSpeechStep() in plugins/elevenlabs/steps/text-to-speech.ts incorrectly maps PCM output formats (pcm_16000, pcm_22050, pcm_24000, pcm_44100) to the MIME type audio/wav, which is incorrect for raw PCM data.

How to reproduce:

// Call textToSpeechStep with a PCM output format
const result = await textToSpeechStep({
  voiceId: "your-voice-id",
  text: "Hello world",
  outputFormat: "pcm_16000" // or pcm_22050, pcm_24000, pcm_44100
});

// result.contentType will be "audio/wav" but should be "audio/L16"

Result: The function returns contentType: "audio/wav" for all PCM formats. However, ElevenLabs' PCM formats return raw S16LE (16-bit signed little-endian) PCM audio data without WAV container headers.

Expected:

• MP3 formats should use audio/mpeg ✓ (already correct)
• PCM formats should use audio/L16 per RFC 2586 and industry standards for raw L16 PCM
• The MIME type audio/wav is incorrect because WAV is a container format with RIFF headers, while ElevenLabs PCM returns headerless raw PCM bytes

References:

• RFC 2586 - The Audio/L16 MIME content type defines audio/L16 as the standard MIME type for raw 16-bit linear PCM audio
• AWS Project Lakechain ElevenLabs documentation explicitly maps PCM formats to audio/L16
• Nuance Mix audio formats documentation uses audio/L16;rate=... for raw PCM audio
• ElevenLabs API documentation states PCM formats are "PCM format (S16LE)" which is consistent with L16

Impact: Downstream systems that validate or process the audio based on the MIME type will incorrectly treat the raw PCM data as a WAV file with container headers, potentially causing decoding failures or incorrect audio processing.