avr-resampler/dist/index.js

Audio Resampler for Agent Voice Response (AVR) STS or TTS service

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.AudioResampler = void 0;
const libsamplerate_js_1 = require("@alexanderolsen/libsamplerate-js");
/**
 * Audio Resampler for STS or TTS service
 * Handles conversion between provider sample rate and client sample rate (8000 Hz)
 */
class AudioResampler {
    constructor(outputSampleRate = 48000) {
        this.inputSampleRate = 8000; // Fixed for client
        this.outputSampleRate = outputSampleRate;
    }
    /**
     * Initialize the downsampler (provider -> client)
     */
    async initialize() {
        console.log(`Initializing downsampler: ${this.outputSampleRate} Hz -> ${this.inputSampleRate} Hz`);
        this.downResampler = await (0, libsamplerate_js_1.create)(1, this.outputSampleRate, this.inputSampleRate, {
            converterType: libsamplerate_js_1.ConverterType.SRC_SINC_BEST_QUALITY, // best quality sinc filter
        });
        console.log(`Initializing upsampler: ${this.inputSampleRate} Hz -> ${this.outputSampleRate} Hz`);
        this.upResampler = await (0, libsamplerate_js_1.create)(1, this.inputSampleRate, this.outputSampleRate, {
            converterType: libsamplerate_js_1.ConverterType.SRC_SINC_BEST_QUALITY, // best quality sinc filter
        });
    }
    /**
     * Convert PCM16 to Float32, downsample, filter and convert back to PCM16
     */
    downsample(pcm) {
        const sampleCount = pcm.length / 2;
        const float32Input = new Float32Array(sampleCount);
        for (let i = 0; i < sampleCount; i++) {
            const int16 = pcm.readInt16LE(i * 2);
            float32Input[i] = int16 / 32768;
        }
        const float32Output = this.downResampler.full(float32Input);
        const int16Output = new Int16Array(float32Output.length);
        for (let i = 0; i < float32Output.length; i++) {
            const s = Math.max(-1, Math.min(1, float32Output[i]));
            int16Output[i] = Math.round(s * 32767);
        }
        return Buffer.from(int16Output.buffer, int16Output.byteOffset, int16Output.byteLength);
    }
    upsample(pcm) {
        const sampleCount = pcm.length / 2; // 16 bit = 2 byte per sample
        const float32Input = new Float32Array(sampleCount);
        // Converti Int16 LE -> Float32 normalizzati (-1.0 a 1.0)
        for (let i = 0; i < sampleCount; i++) {
            const int16 = pcm.readInt16LE(i * 2);
            float32Input[i] = int16 / 32768;
        }
        const float32Output = this.upResampler.full(float32Input);
        const int16Output = new Int16Array(float32Output.length);
        for (let i = 0; i < float32Output.length; i++) {
            const s = Math.max(-1, Math.min(1, float32Output[i]));
            int16Output[i] = Math.round(s * 32767);
        }
        return Buffer.from(int16Output.buffer, int16Output.byteOffset, int16Output.byteLength);
    }
    destroy() {
        this.downResampler.destroy();
        this.upResampler.destroy();
    }
}
exports.AudioResampler = AudioResampler;
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