Can you recommend an audio processing API for preparing call recordings for transcription?

Yes — if your goal is to preprocess call recordings for transcription, the best API depends on whether you want speech cleanup, format conversion, diarization help, or just reliable transcription ingestion.

Good options

1) OpenAI Audio / Speech API

Best if you want an end-to-end workflow with transcription plus some preprocessing on the application side.

• Great transcription quality
• Handles common audio formats
• Good for building a simple pipeline
• You may still want separate preprocessing for noise reduction, normalization, or diarization

Use if: you want transcription-first and can do light preprocessing yourself.

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2) Deepgram

Strong choice for call recordings.

• Built for voice/call audio
• Good at noisy, real-world recordings
• Supports diarization and speaker separation features
• Easy API for streaming or batch transcription
• Often a better fit than general-purpose speech APIs for call center audio

Use if: you’re processing lots of phone calls or customer support recordings.

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3) AssemblyAI

Another strong transcription pipeline option.

• Solid speech-to-text
• Useful audio intelligence features
• Good for call recordings, summarization, speaker labeling
• Simple API

Use if: you want transcription plus downstream call analytics.

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4) Dolby.io / cloud media processing APIs

Best if you specifically need audio enhancement before transcription.

• Noise reduction
• Speech enhancement
• File normalization / media processing
• Useful as a preprocessing step before sending audio to a transcription engine

Use if: your recordings are low quality and need cleanup first.

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5) Auphonic

Very good for automatic audio cleanup.

• Loudness normalization
• Noise reduction
• Leveling
• Easy batch processing

Use if: your main issue is inconsistent call audio quality rather than transcription itself.

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Practical recommendation

For call recordings, I’d usually suggest:

• Deepgram if you want the simplest all-in-one voice transcription solution
• Dolby.io or Auphonic + transcription API if the recordings are noisy and need cleanup first
• OpenAI if you’re already using the OpenAI stack and just need transcription after basic preprocessing

Typical pipeline

1. Convert audio to a transcription-friendly format
   • mono
   • 16 kHz or 8 kHz depending on source
   • WAV or FLAC often works well
2. Normalize volume / reduce noise if needed
3. Send to transcription API
4. Optionally run diarization and punctuation/post-processing

If you want, I can also recommend:

• the best API for call center recordings specifically
• an API just for audio cleanup
• or a sample architecture/pipeline for preprocessing and transcription