@siteed/expo-audio-studio/src/utils/getWavFileInfo.ts

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

// packages/expo-audio-stream/src/utils/getWavFileInfo.ts

import { BitDepth, SampleRate } from '../ExpoAudioStream.types'
import {
    DATA_CHUNK_ID,
    DEFAULT_BIT_DEPTH,
    DEFAULT_SAMPLE_RATE,
    FMT_CHUNK_ID,
    INFO_CHUNK_ID,
    RIFF_HEADER,
    WAVE_HEADER,
} from '../constants'

// Audio format descriptions
const AUDIO_FORMATS: { [key: number]: string } = {
    1: 'PCM',
    3: 'IEEE float',
    6: '8-bit ITU-T G.711 A-law',
    7: '8-bit ITU-T G.711 µ-law',
    65534: 'WAVE_FORMAT_EXTENSIBLE',
}

/**
 * Interface representing the metadata of a WAV file.
 */
export interface WavFileInfo {
    sampleRate: SampleRate
    numChannels: number
    bitDepth: BitDepth
    size: number // in bytes
    durationMs: number // in ms
    audioFormatDescription: string // Description of the audio format
    byteRate: number // Average bytes per second
    blockAlign: number // Number of bytes for one sample including all channels
    creationDateTime?: string // Optional creation date and time
    comments?: string // Optional comments or tags
    compressionType?: string // Optional compression type
    dataChunkOffset: number // Position of the first data chunk
}

/**
 * Extracts metadata from a WAV buffer.
 *
 * @param arrayBuffer - The array buffer containing the WAV data.
 * @returns A promise that resolves to the extracted metadata.
 */
export const getWavFileInfo = async (
    arrayBuffer: ArrayBuffer
): Promise<WavFileInfo> => {
    const view = new DataView(arrayBuffer)

    // Check if the file is a valid RIFF/WAVE file
    const riffHeader = view.getUint32(0, false)
    const waveHeader = view.getUint32(8, false)
    if (riffHeader !== RIFF_HEADER || waveHeader !== WAVE_HEADER) {
        throw new Error('Invalid WAV file')
    }

    // Initialize variables for the metadata
    let fmtChunkOffset = 12
    let sampleRate: SampleRate = DEFAULT_SAMPLE_RATE
    let numChannels = 0
    let bitDepth: BitDepth = DEFAULT_BIT_DEPTH
    let dataChunkSize = 0
    let audioFormat = 0
    let byteRate = 0
    let blockAlign = 0
    let creationDateTime = ''
    let comments = ''
    let dataChunkOffset = 0

    // Parse chunks to find the "fmt " and "data" chunks
    while (fmtChunkOffset < view.byteLength) {
        const chunkId = view.getUint32(fmtChunkOffset, false)
        const chunkSize = view.getUint32(fmtChunkOffset + 4, true)
        if (chunkId === FMT_CHUNK_ID) {
            // "fmt "
            audioFormat = view.getUint16(fmtChunkOffset + 8, true)
            if (!AUDIO_FORMATS[audioFormat]) {
                throw new Error('Unsupported WAV file format')
            }
            numChannels = view.getUint16(fmtChunkOffset + 10, true)
            sampleRate = view.getUint32(fmtChunkOffset + 12, true) as SampleRate
            byteRate = view.getUint32(fmtChunkOffset + 16, true)
            blockAlign = view.getUint16(fmtChunkOffset + 20, true)
            bitDepth = view.getUint16(fmtChunkOffset + 22, true) as BitDepth
        } else if (chunkId === DATA_CHUNK_ID) {
            // "data"
            dataChunkSize = chunkSize
            dataChunkOffset = fmtChunkOffset + 8 // Position after chunk header
            break
        } else if (chunkId === INFO_CHUNK_ID) {
            // "INFO"
            // Read INFO chunk (assuming it contains a text-based creation date/time and comments)
            const infoStart = fmtChunkOffset + 8
            const infoText = new TextDecoder().decode(
                new Uint8Array(
                    arrayBuffer.slice(infoStart, infoStart + chunkSize)
                )
            )
            const infoParts = infoText.split('\0')
            creationDateTime = infoParts[0]
            comments = infoParts[1]
        }
        fmtChunkOffset += 8 + chunkSize
    }

    if (!sampleRate || !numChannels || !bitDepth || !dataChunkSize) {
        throw new Error('Incomplete WAV file information')
    }

    // Calculate duration
    const bytesPerSample = bitDepth / 8
    const numSamples = dataChunkSize / (numChannels * bytesPerSample)
    const durationMs = (numSamples / sampleRate) * 1000

    return {
        sampleRate,
        numChannels,
        bitDepth,
        size: arrayBuffer.byteLength,
        durationMs,
        audioFormatDescription: AUDIO_FORMATS[audioFormat],
        byteRate,
        blockAlign,
        creationDateTime: creationDateTime || undefined,
        comments: comments || undefined,
        compressionType:
            audioFormat === 1 ? 'None' : AUDIO_FORMATS[audioFormat],
        dataChunkOffset,
    }
}