fast-transcription

name	fast-transcription
description	Azure AI Speech Fast Transcription - Transcribe contact center calls with speaker identification using stereo channel separation or mono diarization. Returns results synchronously and faster than real-time.
version	1.0.0
triggers	["fast transcription","speech to text","call transcription","contact center transcription","audio transcription","stereo transcription","diarization","speaker identification","azure speech api"]
tools	["vscode","execute","read","edit","search","web","agent","memory","todo","pw/*","c7/*"]
model	Claude Opus 4.5 (copilot)

Fast Transcription Skill

Folder Contents

File	Type	Description
SKILL.md	Documentation	Main skill documentation with API reference, speaker ID strategies, and curl examples
PRD.md	Documentation	Product Requirements Document for the skill
.env.sample	Configuration	Sample environment variables (AZURE_AI_SPEECH_ENDPOINT, AZURE_AI_SPEECH_KEY)
requirements.txt	Dependencies	Python package dependencies (requests, python-dotenv, pydub)
scripts/
scripts/__init__.py	Module	Package initializer with exports
scripts/transcription_client.py	Client	Core API client with both stereo and diarization strategies
scripts/stereo_transcriber.py	Transcriber	Stereo channel separation for pre-separated audio (agent on ch0, customer on ch1)
scripts/diarization_transcriber.py	Transcriber	Mono diarization for mixed-speaker recordings with 2-36 speaker support
scripts/contact_center_processor.py	Pipeline	Full contact center pipeline with speaker labeling and call analytics

---

CRITICAL: No Mock Functionality

ALL implementations must be real and fully connected to Azure services.

• NO mock transcription results
• NO fake speaker labels
• NO simulated audio processing
• NO placeholder transcripts
• NO hardcoded diarization output

Everything must connect to real Azure AI Speech Fast Transcription API and return real results.

If any functionality cannot be implemented with real connections (e.g., missing credentials, audio files unavailable), STOP and confirm with the user before proceeding.

---

Overview

Azure AI Speech Fast Transcription API provides synchronous, faster-than-real-time transcription ideal for contact center recordings. Unlike batch transcription which requires polling, results are returned immediately.

API Reference

Property	Value
Endpoint	https://{region}.api.cognitive.microsoft.com/speechtotext/transcriptions:transcribe
API Version	2025-10-15
Max Audio	2 hours, 300 MB
Formats	WAV, MP3, FLAC, OGG, AAC
Auth Header	Ocp-Apim-Subscription-Key

Speaker Identification Strategies

Strategy A: Stereo Channel Separation

For recordings where speakers are pre-separated on audio channels (e.g., agent on channel 0, customer on channel 1):

definition = {
    "locales": ["en-US"],
    "channels": [0, 1]  # Transcribe each channel independently
}

Advantages:

• ~10% higher accuracy than diarization
• Handles overlapping speech cleanly
• No algorithmic guessing about speakers

Strategy B: Mono Diarization

For single-channel recordings with mixed speakers:

definition = {
    "locales": ["en-US"],
    "diarization": {
        "enabled": True,
        "maxSpeakers": 2  # 2-36 speakers supported
    }
}

Considerations:

• Relies on algorithms to detect "who spoke when"
• Can struggle with simultaneous speech or similar voices
• Set maxSpeakers to expected count for best results

Environment Variables

# Required
AZURE_AI_SPEECH_ENDPOINT=https://swedencentral.api.cognitive.microsoft.com/
AZURE_AI_SPEECH_KEY=your-speech-api-key

# Optional - for embedding transcripts
AZURE_OPENAI_ENDPOINT=https://your-resource.openai.azure.com/
AZURE_OPENAI_API_KEY=your-openai-key
AZURE_OPENAI_EMBEDDING_DEPLOYMENT=text-embedding-3-large

Building Block Scripts

Script	Purpose
transcription_client.py	Core API client with both strategies
stereo_transcriber.py	Stereo channel separation for contact center calls
diarization_transcriber.py	Mono diarization for mixed-speaker recordings
contact_center_processor.py	Full pipeline with speaker labeling and analytics

Quick Start

Basic Transcription

from scripts.transcription_client import TranscriptionClient

client = TranscriptionClient()

# Transcribe with stereo channels
result = client.transcribe_stereo("call_recording.wav")
print(f"Channel 0 (Agent): {result.channels[0].text}")
print(f"Channel 1 (Customer): {result.channels[1].text}")

Mono with Diarization

from scripts.transcription_client import TranscriptionClient

client = TranscriptionClient()

# Transcribe with speaker diarization
result = client.transcribe_with_diarization("mono_call.wav", max_speakers=2)
for phrase in result.phrases:
    print(f"Speaker {phrase.speaker}: {phrase.text}")

Contact Center Pipeline

from scripts.contact_center_processor import ContactCenterProcessor

processor = ContactCenterProcessor()
call_analysis = processor.process_call(
    audio_file="call.wav",
    strategy="stereo",  # or "diarization"
    agent_channel=0,
    customer_channel=1
)

print(f"Agent Transcript: {call_analysis.agent_transcript}")
print(f"Customer Transcript: {call_analysis.customer_transcript}")
print(f"Call Duration: {call_analysis.duration_seconds}s")

REST API Examples

curl - Stereo Channels

curl --location 'https://swedencentral.api.cognitive.microsoft.com/speechtotext/transcriptions:transcribe?api-version=2025-10-15' \
--header 'Content-Type: multipart/form-data' \
--header 'Ocp-Apim-Subscription-Key: YOUR_KEY' \
--form 'audio=@"call_recording.wav"' \
--form 'definition="{\"locales\":[\"en-US\"], \"channels\": [0,1]}"'

curl - Mono Diarization

curl --location 'https://swedencentral.api.cognitive.microsoft.com/speechtotext/transcriptions:transcribe?api-version=2025-10-15' \
--header 'Content-Type: multipart/form-data' \
--header 'Ocp-Apim-Subscription-Key: YOUR_KEY' \
--form 'audio=@"mono_call.wav"' \
--form 'definition="{\"locales\":[\"en-US\"], \"diarization\": {\"maxSpeakers\": 2, \"enabled\": true}}"'

Response Structure

Stereo Response

{
  "duration": "PT1M23S",
  "combinedPhrases": [
    {"channel": 0, "text": "Full text from channel 0"},
    {"channel": 1, "text": "Full text from channel 1"}
  ],
  "phrases": [
    {
      "channel": 0,
      "offset": "PT0.5S",
      "duration": "PT2.3S",
      "text": "Hello, thank you for calling."
    }
  ]
}

Diarization Response

{
  "duration": "PT1M23S",
  "combinedPhrases": [
    {"speaker": 1, "text": "Full text from speaker 1"},
    {"speaker": 2, "text": "Full text from speaker 2"}
  ],
  "phrases": [
    {
      "speaker": 1,
      "offset": "PT0.5S",
      "duration": "PT2.3S",
      "text": "Hello, how can I help you today?"
    }
  ]
}

Contact Center Use Cases

Quality Assurance Automation

Enable 100% call coverage vs. traditional 2-4 calls per agent per month. Companies report 20-30% cost savings.

Compliance Monitoring

Automatically verify mandatory disclosures, script adherence, and PII handling. Essential for HIPAA, PCI-DSS, GDPR.

Agent Coaching

Identify specific strengths and weaknesses with data-driven feedback within hours.

Customer Sentiment Analysis

Detect early signs of dissatisfaction for proactive retention efforts.

Post-Call Summarization

Auto-generate call summaries with reason for contact, steps taken, and resolution.

Free Audio Sample Sources

Source	Type	License	Best For
VoxConverse	Mono, multi-speaker	CC BY 4.0	Diarization testing
AMI Corpus	Mono, meeting recordings	CC BY 4.0	Multi-participant scenarios
LibriSpeech	Mono, single speaker	CC BY 4.0	Synthesizing stereo files

Lessons Learned

Region Selection

Fast Transcription is available in limited regions. Use East US, West Europe, or Southeast Asia for best availability.

Audio Format

Convert to 16-bit WAV, 16kHz for best compatibility. API accepts MP3, FLAC, OGG, AAC but WAV is most reliable.

Channel Configuration

For stereo recordings, channels: [0, 1] transcribes both channels independently. Use channels: [0] for left-only.

Diarization Accuracy

Set maxSpeakers to the known count. Setting it higher than actual speakers can reduce accuracy.

Rate Limiting

Free tier provides 5 audio hours/month. For training sessions, use 30-60 second samples to avoid quota exhaustion.

Error Handling

Common errors:

• HTTP 401/403: Key doesn't match region
• HTTP 429: Rate limited - stagger requests
• Audio format rejected: Convert to 16-bit WAV

Dependencies

requests>=2.31.0
python-dotenv>=1.0.0
pydub>=0.25.1  # Optional, for audio format conversion

References

• Fast Transcription API Guide
• REST API Reference
• Call Center Overview
• VoxConverse Dataset