Transcribing Telegram voice messages using Whisper and Gemini with a fallback mechanism

🎙️ n8n Workflow: Voice Message Transcription with Access Control

This n8n workflow enables automated transcription of voice messages in Telegram groups with built-in access control and intelligent fallback mechanisms. It's designed for teams that need to convert audio messages to text while maintaining security and handling various audio formats.

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📌 Section 1: Trigger & Access Control

⚡ Receive Message (Telegram Trigger)

Purpose: Captures incoming messages from users in your Telegram group.

How it works: When a user sends a message (voice, audio, or text), the workflow is triggered and the sender's information is captured.

Benefit: Serves as the entry point for the entire transcription pipeline.

🔐 Sender Verification

Purpose: Validates whether the sender has permission to use the transcription service.

Logic: Check sender against authorized users list If authorized → Proceed to next step If not authorized → Send "Access denied" message and stop workflow

Benefit: Prevents unauthorized users from consuming AI credits and accessing the service.

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📌 Section 2: Message Type Detection

🎵 Audio/Voice Recognition

Purpose: Identifies the type of incoming message and audio format.

Why it's needed: Telegram handles different audio types with different statuses:

• Voice notes (voice messages)
• Audio files (standard audio attachments)
• Text messages (no audio content)

Process:

1. Check if message contains audio/voice content
2. If no audio file detected → Send "No audio file found" message
3. If audio detected → Assign file ID and proceed to format detection

🧩 File Type Determination (IF Node)

Purpose: Identifies the specific audio format for proper processing.

Supported formats:

• OGG (Telegram voice messages)
• MPEG/MP3
• MP4/M4A
• Other audio formats

Logic:

If format recognized → Proceed to transcription If format not recognized → Send "File format not recognized" message

Benefit: Ensures compatibility with transcription services by validating file types upfront.

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📌 Section 3: Primary Transcription (OpenAI)

📥 File Download

Purpose: Downloads the audio file from Telegram for processing.

🤖 OpenAI Transcription

Purpose: Transcribes audio to text using OpenAI's Whisper API.

Why OpenAI: High-quality transcription with cost-effective pricing.

Process:

1. Send downloaded file to OpenAI transcription API
2. Simultaneously send notification: "Transcription started"
3. If successful → Assign transcribed text to variable and proceed
4. If error occurs → Trigger fallback mechanism

Benefit: Fast, accurate transcription with multi-language support.

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📌 Section 4: Fallback Transcription (Gemini)

🛟 Gemini Backup Transcription

Purpose: Provides a safety net if OpenAI transcription fails.

Process:

1. Receives file only if OpenAI node returns an error
2. Downloads and processes the same audio file
3. Sends to Google Gemini for transcription
4. Assigns transcribed text to the same text variable

Benefit: Ensures high reliability—if one service fails, the other takes over automatically.

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📌 Section 5: Message Length Handling

📏 Text Length Check (IF Node)

Purpose: Determines if the transcribed text exceeds Telegram's character limit.

Logic:

If text ≤ 4000 characters → Send directly to Telegram If text > 4000 characters → Split into chunks

Why: Telegram has a 4,000-character limit per message.

✂️ Text Splitting (Code Node)

Purpose: Breaks long transcriptions into 4,000-character segments.

Process:

1. Receives text longer than 4,000 characters
2. Splits text into chunks of ≤4,000 characters
3. Maintains readability by avoiding mid-word breaks
4. Outputs array of text chunks

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📌 Section 6: Response Delivery

💬 Send Transcription (Telegram Node)

Purpose: Delivers the transcribed text back to the Telegram group.

Behavior:

• Short messages: Sent as a single message
• Long messages: Sent as multiple sequential messages

Benefit: Users receive complete transcriptions regardless of length, ensuring no content is lost.

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📊 Workflow Overview Table

Section	Node Name	Purpose
1. Trigger	Receive Message	Captures incoming Telegram messages
2. Access Control	Sender Verification	Validates user permissions
3. Detection	Audio/Voice Recognition	Identifies message type and audio format
4. Validation	File Type Check	Verifies supported audio formats
5. Download	File Download	Retrieves audio file from Telegram
6. Primary AI	OpenAI Transcription	Main transcription service
7. Fallback AI	Gemini Transcription	Backup transcription service
8. Processing	Text Length Check	Determines if splitting is needed
9. Splitting	Code Node	Breaks long text into chunks
10. Response	Send to Telegram	Delivers transcribed text

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🎯 Key Benefits

• 🔐 Secure access control: Only authorized users can trigger transcriptions
• 💰 Cost management: Prevents unauthorized credit consumption
• 🎵 Multi-format support: Handles various Telegram audio types
• 🛡️ High reliability: Dual-AI fallback ensures transcription success
• 📱 Telegram-optimized: Automatically handles message length limits
• 🌍 Multi-language: Both AI services support numerous languages
• ⚡ Real-time notifications: Users receive status updates during processing
• 🔄 Automatic chunking: Long transcriptions are intelligently split
• 🧠 Smart routing: Files are processed through the optimal path
• 📊 Complete delivery: No content loss regardless of transcription length

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🚀 Use Cases

• Team meetings: Transcribe voice notes from team discussions
• Client communications: Convert client voice messages to searchable text
• Documentation: Create text records of verbal communications
• Accessibility: Make audio content accessible to all team members
• Multi-language teams: Leverage AI transcription for various languages