Showing posts with label NLP Terms. Show all posts
Showing posts with label NLP Terms. Show all posts

Wednesday, 23 July 2025

Building a Speech Recognition System with VOSK: A Step-by-Step Guide

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In a world driven by voice interfaces—from smart assistants to transcription tools; speech recognition is a key component of modern AI. VOSK is an open-source speech recognition toolkit that makes it incredibly easy to build fast and accurate offline voice systems, even on low-resource devices like Raspberry Pi.

Whether you're a beginner or looking to integrate voice into your next project, this blog will guide you step-by-step on using VOSK effectively.


What is VOSK?

VOSK is a lightweight, offline-capable speech recognition engine based on Kaldi. It supports:

  • 20+ languages (English, Hindi, Spanish, etc.)
  • Python, Java, JavaScript, C# APIs
  • Offline recognition (no internet required)
  • Real-time transcription

GitHub: VOSK GitHub Repo

Python Docs: Python Docs



Prerequisites

Before getting started, make sure you have the following:

  • Python 3.6+
  • pip package manager
  • A microphone (optional for live recognition)
  • OS: Linux, Windows, macOS or Raspberry Pi

Step 1: Install VOSK API

bash

pip install vosk

Optionally, install PyAudio for microphone input:


pip install pyaudio

On Linux, you may need:

sudo apt install portaudio19-dev python3-pyaudio


Step 2: Download a Pretrained Model

You can find models here: VOSK Models

Example for English (small):

wget https://alphacephei.com/vosk/models/vosk-model-small-en-us-0.15.zip unzip vosk-model-small-en-us-0.15.zip

For Raspberry Pi, use vosk-model-small-en-us-0.15
For high accuracy, try vosk-model-en-us-0.22 (~1.4GB)


 Step 3: Transcribe from Audio File

Here's a basic Python script to transcribe audio:

from vosk import Model, KaldiRecognizer import wave import json wf = wave.open("test.wav", "rb") model = Model("vosk-model-small-en-us-0.15") rec = KaldiRecognizer(model, wf.getframerate()) while True: data = wf.readframes(4000) if len(data) == 0: break if rec.AcceptWaveform(data): print(rec.Result()) print(rec.FinalResult())

 Make sure your audio file is:

  • Mono
  • 16-bit PCM
  • 16000 Hz sample rate

Use ffmpeg to convert:

ffmpeg -i your_audio.mp3 -ar 16000 -ac 1 -c:a pcm_s16le test.wav


Step 4: Real-Time Microphone Transcription

import pyaudio from vosk import Model, KaldiRecognizer model = Model("vosk-model-small-en-us-0.15") rec = KaldiRecognizer(model, 16000) p = pyaudio.PyAudio() stream = p.open(format=pyaudio.paInt16, channels=1, rate=16000, input=True, frames_per_buffer=8000) stream.start_stream() print("Speak now...") while True: data = stream.read(4000, exception_on_overflow=False) if rec.AcceptWaveform(data): print(rec.Result())


Step 5: Multilingual Support

Want Odia, Hindi, or Spanish?

Just download the corresponding model:

  • Hindi: vosk-model-small-hi-0.4
  • Odia: [Custom training required]
  • Spanish: vosk-model-small-es-0.42

Usage remains the same—just switch the model path.

Step 6: Custom Vocabulary (Limited Grammar)

To improve accuracy on known phrases:

rec = KaldiRecognizer(model, 16000, '["hello", "world", "turn on light"]')

This helps for command-based interfaces or limited-domain apps.


Step 7: Integrate into Applications

  • Home Automation: Use recognized text to trigger GPIO or MQTT
  • Chatbot: Convert voice to text for chatbot input
  • Transcriber: Save output to .txt or .json
  • Call Monitor: Analyze phone calls (recorded) in real-time


Raspberry Pi Setup



On a Raspberry Pi (Zero 2 W or 4):

pip install vosk sudo apt install ffmpeg portaudio19-dev python3-pyaudio

Use a small model (<50MB) for optimal performance.


 What’s Next?

  •  Fine-tune or train a model with Kaldi (advanced)
  •  Use Whisper or DeepSpeech for larger models (cloud-based)
  •  Use G2P + phonemizer for custom languages like Odia

VOSK is a simple, powerful way to bring speech recognition into your projects without the internet. Its cross-platform support, Python-first approach, and offline models make it perfect for embedded and edge AI systems.

Whether you're building a smart assistant, transcription tool, or creative audio app—VOSK is a brilliant starting point.


Resources:



Monday, 14 July 2025

Demystifying AI & LLM Buzzwords: Speak AI Like a Pro

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Artificial Intelligence (AI) and Large Language Models (LLMs) are everywhere now; starting from smart assistants to AI copilots, chatbots, and content generators. If you’re in tech, product, marketing, or just exploring this space, understanding the jargon is essential to join meaningful conversations.

Here’s a breakdown of must-know AI and LLM terms, with simple explanations so you can talk confidently in any meeting or tweet storm.

Core AI Concepts

1. Artificial Intelligence (AI)

AI is the simulation of human intelligence in machines. It includes learning, reasoning, problem-solving, and perception.

2. Machine Learning (ML)

A subset of AI that allows systems to learn from data and improve over time without explicit programming.

3. Deep Learning

A type of ML using neural networks with multiple layers—great for recognizing patterns in images, text, and voice.

LLM & NLP Essentials

4. Large Language Model (LLM)

An AI model trained on massive text datasets to understand, generate, and manipulate human language. Examples: GPT-4, Claude, Gemini, LLaMA.

5. Transformer Architecture

The foundation of modern LLMs—introduced by Google’s paper “Attention Is All You Need”. It enables parallel processing and context understanding in text.

6. Token

A piece of text (word, sub-word, or character) processed by an LLM. LLMs think in tokens, not words.

7. Prompt

The input given to an LLM to generate a response. Prompt engineering is the art of crafting effective prompts.

8. Zero-shot / Few-shot Learning

  • Zero-shot: The model responds without any example.
  • Few-shot: The model is shown a few examples to learn the pattern.

Training & Fine-Tuning Jargon

9. Pretraining

LLMs are first trained on general datasets (like Wikipedia, books, web pages) to learn language patterns.

10. Fine-tuning

Adjusting a pretrained model on specific domain data for better performance (e.g., medical, legal).

11. Reinforcement Learning with Human Feedback (RLHF)

Used to align AI output with human preferences by training it using reward signals from human evaluations.

Deployment & Use Cases

12. Inference

Running the model to get a prediction or output (e.g., generating text from a prompt).

13. Latency

Time taken by an LLM to respond to a prompt. Critical for real-time applications.

14. Context Window

The maximum number of tokens a model can handle at once. GPT-4 can go up to 128k tokens in some versions.

AI Ops & Optimization

15. RAG (Retrieval-Augmented Generation)

Combines search and generation. Useful for making LLMs fetch up-to-date or domain-specific info before answering.

16. Embeddings

Numerical vector representations of text that capture semantic meaning—used for search, clustering, and similarity comparison.

17. Vector Database

A special database (like Pinecone, Weaviate) for storing embeddings and retrieving similar documents.

Governance & Safety

18. Hallucination

When an LLM confidently gives wrong or made-up information. A major challenge in production use.

19. Bias

LLMs can reflect societal or training data biases—gender, race, politics—leading to ethical concerns.

20. AI Alignment

The effort to make AI systems behave in ways aligned with human values, safety, and intent.

Some Bonus Buzzwords For You...

  • CoT (Chain of Thought Reasoning): For better logic in complex tasks.
  • Agents: LLMs acting autonomously to complete tasks using tools, memory, and planning.
  • Multi-modal AI: Models that understand multiple data types—text, image, audio (e.g., GPT-4o, Gemini 1.5).
  • Open vs. Closed Models: Open-source (LLaMA, Mistral) vs proprietary (GPT, Claude).
  • Prompt Injection: A vulnerability where malicious input manipulates an LLM’s output.


Here is the full list of AI & LLM Buzzwords with Descriptions in table format for your reference:

Buzzword Description
AI (Artificial Intelligence) Simulation of human intelligence in machines that perform tasks like learning and reasoning.
ML (Machine Learning) A subset of AI where models learn from data to improve performance without being explicitly programmed.
DL (Deep Learning) A type of machine learning using multi-layered neural networks for tasks like image or speech recognition.
AGI (Artificial General Intelligence) AI with the ability to understand, learn, and apply knowledge in a generalized way like a human.
Narrow AI AI designed for a specific task, like facial recognition or language translation.
Supervised Learning Machine learning with labeled data used to train a model.
Unsupervised Learning Machine learning using input data without labeled responses.
Reinforcement Learning Training an agent to make decisions by rewarding desirable actions.
Federated Learning A decentralized training approach where models learn across multiple devices without data sharing.
LLM (Large Language Model) AI models trained on large text corpora to generate and understand human-like text.
NLP (Natural Language Processing) Technology for machines to understand, interpret, and generate human language.
Transformers A neural network architecture that handles sequential data with attention mechanisms.
BERT A transformer-based model designed for understanding the context of words in a sentence.
GPT A generative language model that creates human-like text based on input prompts.
Tokenization Breaking down text into smaller units (tokens) for processing by LLMs.
Attention Mechanism Allows models to focus on specific parts of the input sequence when making predictions.
Self-Attention A mechanism where each word in a sentence relates to every other word to understand context.
Pretraining Initial training of a model on a large corpus before fine-tuning for specific tasks.
Fine-tuning Adapting a pretrained model to a specific task using domain-specific data.
Zero-shot Learning The model performs tasks without seeing any examples during training.
Few-shot Learning The model learns a task using only a few labeled examples.
Prompt Engineering Designing input prompts to guide LLM output effectively.
Prompt Tuning Optimizing prompts using automated techniques to improve model responses.
Instruction Tuning Training LLMs to follow user instructions more accurately.
Context Window The maximum number of tokens a model can process in one input.
Hallucination When an LLM generates incorrect or made-up information.
Chain of Thought (CoT) Technique that enables models to reason through intermediate steps.
Function Calling Enabling models to call APIs or tools during response generation.
AI Agents Autonomous systems powered by LLMs that can perform tasks and use tools.
AutoGPT An experimental system that chains together LLM calls to complete goals autonomously.
LangChain Framework for building LLM-powered apps with memory, tools, and agent logic.
Semantic Search Search method using the meaning behind words instead of exact keywords.
Retrieval-Augmented Generation (RAG) Combines information retrieval with LLMs to generate context-aware responses.
Embeddings Numerical vectors representing the semantic meaning of text.
Vector Database A database optimized for storing and querying embeddings.
Chatbot An AI program that simulates conversation with users.
Copilot AI assistant integrated in software tools to help users with tasks.
Multi-modal Models AI models that process text, image, and audio inputs together.
AI Plugin Extensions that allow LLMs to interact with external tools or services.
Text-to-Image Generating images from text descriptions.
Text-to-Speech Converting text into spoken audio using AI.
Speech-to-Text Transcribing spoken audio into text.
Inference The process of running a trained model to make predictions or generate outputs.
Latency Time taken by an AI model to produce a response.
Throughput Amount of data a model can process in a given time.
Model Quantization Reducing model size by converting weights to lower precision.
Distillation Creating smaller models that mimic larger ones while maintaining performance.
Model Pruning Removing unnecessary weights or neurons to reduce model complexity.
Checkpointing Saving intermediate model states to resume or analyze training.
A/B Testing Experimenting with two model versions to compare performance.
FTaaS (Fine-tuning as a Service) Hosted services for custom model training.
Bias Unintended prejudice or skew in AI outputs due to biased training data.
Toxicity Offensive, harmful, or inappropriate content generated by AI.
Red-teaming Testing AI systems for vulnerabilities and risky behavior.
AI Alignment Ensuring AI systems behave in accordance with human values.
Content Moderation Filtering or flagging harmful or inappropriate AI outputs.
Guardrails Rules and constraints placed on AI outputs for safety.
Prompt Injection A method to manipulate AI by embedding hidden instructions in user input.
Model Explainability Making AI model decisions understandable to humans.
Interpretability Understanding how and why a model makes specific predictions.
Safety Layer Additional control mechanisms to reduce risks in AI output.
Fairness Ensuring AI does not discriminate or favor unfairly across different user groups.
Differential Privacy Techniques to ensure individual data can't be reverse-engineered from AI outputs.

Whether you’re building with AI or just starting your journey, knowing these concepts helps you:

  • Communicate with engineers and researchers
  • Ask better questions
  • Make smarter product or investment decisions


Sources & Bibliography

OpenAI Blog – For GPT, prompt engineering, RLHF, and safety

Google AI Blog – For BERT and transformer models
Vaswani et al. (2017) – “Attention Is All You Need” paper
GPT-3 Paper (Brown et al., 2020) – Few-shot learning and language models
Stanford CS224N – Natural Language Processing with Deep Learning course
Hugging Face Docs – LLMs, embeddings, tokenization, and transformers
LangChain Docs – For RAG, AI agents, and tool usage
AutoGPT GitHub – Open-source AI agent framework
Pinecone Docs – Embeddings and vector search explained
Microsoft Research – Responsible AI – Bias, fairness, and alignment