@siteed/expo-audio-studio/build/AudioAnalysis/extractMelSpectrogram.js

Comprehensive audio processing library for React Native and Expo with recording, analysis, visualization, and streaming capabilities across iOS, Android, and web

/**
 * @experimental This feature is experimental and currently only available on Android.
 * The API may change in future versions. The web implementation is a placeholder.
 */
import { ExpoAudioStreamModule } from '..';
import { isWeb } from '../constants';
import { processAudioBuffer, } from '../utils/audioProcessing';
/**
 * Extracts a mel spectrogram from audio data
 *
 * @experimental This feature is experimental and currently only available on Android.
 * The iOS implementation will throw an "UNSUPPORTED_PLATFORM" error.
 * The web implementation is a placeholder that returns dummy data.
 */
export async function extractMelSpectrogram(options) {
    const { fileUri, arrayBuffer, windowSizeMs, hopLengthMs, nMels, fMin = 0, fMax, windowType = 'hann', normalize = false, logScale = true, decodingOptions, startTimeMs, endTimeMs, logger, } = options;
    if (isWeb) {
        // Create audio context
        const audioContext = new (window.AudioContext ||
            window.webkitAudioContext)();
        try {
            // Process audio data using the existing utility
            const processedAudio = await processAudioBuffer({
                arrayBuffer,
                fileUri,
                targetSampleRate: decodingOptions?.targetSampleRate || 16000,
                targetChannels: decodingOptions?.targetChannels || 1,
                normalizeAudio: decodingOptions?.normalizeAudio ?? false,
                startTimeMs,
                endTimeMs,
                audioContext,
                logger: options.logger,
            });
            // Calculate window and hop size in samples
            const sampleRate = processedAudio.sampleRate;
            const windowSize = Math.floor((windowSizeMs * sampleRate) / 1000);
            const hopLength = Math.floor((hopLengthMs * sampleRate) / 1000);
            const maxFreq = fMax || sampleRate / 2;
            // Extract the mel spectrogram from the processed audio
            const spectrogram = computeMelSpectrogram(processedAudio.channelData, sampleRate, nMels, windowSize, hopLength, fMin, maxFreq, windowType, normalize, logScale);
            const timeSteps = spectrogram.length;
            return {
                spectrogram,
                sampleRate,
                nMels,
                timeSteps,
                durationMs: processedAudio.durationMs,
            };
        }
        catch (error) {
            logger?.error('Error extracting mel spectrogram:', error);
            throw error;
        }
        finally {
            // Close the audio context
            await audioContext.close();
        }
    }
    return ExpoAudioStreamModule.extractMelSpectrogram(options);
}
/**
 * Computes a mel spectrogram from audio data
 *
 * @experimental This is a placeholder implementation that returns dummy data.
 * The actual implementation will be added in a future version.
 */
function computeMelSpectrogram(audioData, sampleRate, nMels, windowSize, hopLength, fMin, fMax, windowType, normalize, logScale) {
    // Placeholder for the actual implementation
    // This would include:
    // 1. Windowing the audio data using the specified window type
    // 2. Computing the STFT (Short-Time Fourier Transform)
    // 3. Converting to power spectrogram
    // 4. Applying mel filterbanks
    // 5. Taking the logarithm if logScale is true
    // 6. Normalizing if normalize is true
    // For now, return a dummy implementation
    const numFrames = Math.floor((audioData.length - windowSize) / hopLength) + 1;
    const spectrogram = [];
    // Create dummy mel spectrogram data
    for (let i = 0; i < numFrames; i++) {
        spectrogram.push(Array(nMels).fill(0));
    }
    return spectrogram;
}
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