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| 1 | +// requires: wasm-media-encoders |
| 2 | +import { createMp3Encoder } from 'wasm-media-encoders' |
| 3 | + |
| 4 | +/** |
| 5 | + * MP3 encoder — browser + Node, via wasm-media-encoders |
| 6 | + * |
| 7 | + * @param {Object} opts |
| 8 | + * @param {number} opts.sampleRate - required |
| 9 | + * @param {number} [opts.bitrate=128] - kbps (CBR) |
| 10 | + * @param {number} [opts.quality] - 0-9 VBR quality (0=best, 9=worst). If set, uses VBR mode. |
| 11 | + * @param {number} [opts.channels] - 1 or 2 |
| 12 | + * @returns {{ encode, flush, free }} |
| 13 | + * |
| 14 | + * encode(channels: Float32Array[]) → Uint8Array |
| 15 | + * flush() → Uint8Array |
| 16 | + * free() → void |
| 17 | + */ |
| 18 | +export default async function mp3(opts) { |
| 19 | + let { sampleRate, bitrate = 128, quality, channels } = opts |
| 20 | + if (!channels || channels < 1 || channels > 2) channels = 2 |
| 21 | + |
| 22 | + let encoder = await createMp3Encoder() |
| 23 | + |
| 24 | + let cfg = { sampleRate, channels } |
| 25 | + if (quality != null) cfg.vbrQuality = quality |
| 26 | + else cfg.bitrate = bitrate |
| 27 | + |
| 28 | + encoder.configure(cfg) |
| 29 | + |
| 30 | + // WASM encoder has ~320MB/channel buffer limit. |
| 31 | + // Chunk large inputs in 1152*1024 (~1.18M) sample blocks. |
| 32 | + const CHUNK = 1152 * 1024 |
| 33 | + |
| 34 | + return { encode, flush, free } |
| 35 | + |
| 36 | + function encode(ch) { |
| 37 | + let n = ch[0].length |
| 38 | + if (n <= CHUNK) { |
| 39 | + let raw = encoder.encode(ch) |
| 40 | + return new Uint8Array(raw) |
| 41 | + } |
| 42 | + let parts = [] |
| 43 | + for (let i = 0; i < n; i += CHUNK) { |
| 44 | + let end = Math.min(i + CHUNK, n) |
| 45 | + let slice = ch.map(c => c.subarray(i, end)) |
| 46 | + let raw = encoder.encode(slice) |
| 47 | + if (raw.length) parts.push(new Uint8Array(raw)) |
| 48 | + } |
| 49 | + let total = 0 |
| 50 | + for (let p of parts) total += p.length |
| 51 | + let out = new Uint8Array(total) |
| 52 | + let off = 0 |
| 53 | + for (let p of parts) { out.set(p, off); off += p.length } |
| 54 | + return out |
| 55 | + } |
| 56 | + |
| 57 | + function flush() { |
| 58 | + let raw = encoder.finalize() |
| 59 | + return new Uint8Array(raw) |
| 60 | + } |
| 61 | + |
| 62 | + function free() { |
| 63 | + encoder = null |
| 64 | + } |
| 65 | +} |
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