feuerwerk/tests/core/ogg.test.ts

/**
 * Opus in Ogg as a bake is kept (#340): the pages around the packets, their checksums, where each
 * page says it has got to, and the pre-skip and length a decoder trims by.
 */
import { describe, expect, it } from 'vitest';
import {
  OggOpusReader,
  oggCrc,
  oggOpus,
  opusHead,
  opusPacketSamples,
  preSkipOf,
  readOggOpus,
} from '../../src/core/music/ogg';

const packet = (size: number, fill: number) => ({ data: new Uint8Array(size).fill(fill), samples: 960 });

/** The flags and the granule position of every page, in order. */
function pagesOf(file: Uint8Array): { flags: number; granule: number }[] {
  const view = new DataView(file.buffer);
  const pages: { flags: number; granule: number }[] = [];
  for (let at = 0; at < file.length;) {
    pages.push({ flags: file[at + 5]!, granule: view.getUint32(at + 6, true) });
    const count = file[at + 26]!;
    at += 27 + count + file.subarray(at + 27, at + 27 + count).reduce((s, v) => s + v, 0);
  }
  return pages;
}

describe('Opus in Ogg', () => {
  it('checks a page with the CRC Ogg uses', () => {
    expect(oggCrc(Uint8Array.from('123456789', (c) => c.charCodeAt(0)))).toBe(0x89a1897f);
  });

  it('reads back the head, the packets and the length it was given', () => {
    const packets = [packet(3, 1), packet(255, 2), packet(600, 3), packet(0, 4)];
    const file = oggOpus({ channels: 2, preSkip: 312, frames: 3000, packets });
    const back = readOggOpus(file);
    expect(back.channels).toBe(2);
    expect(back.preSkip).toBe(312);
    expect(back.granule).toBe(312 + 3000);
    expect(back.packets.map((p) => [p.length, p[0] ?? -1])).toEqual([
      [3, 1],
      [255, 2],
      [600, 3],
      [0, -1],
    ]);
  });

  it('opens with the head alone, flags the first and the last page', () => {
    const file = oggOpus({ channels: 1, preSkip: 312, frames: 960, packets: [packet(10, 1)] });
    expect(String.fromCharCode(...file.subarray(28, 36))).toBe('OpusHead');
    expect(pagesOf(file).map((page) => page.flags)).toEqual([0x02, 0x00, 0x04]);
  });

  it('starts a new page before 255 lacing values, each counting the samples finished on it', () => {
    const packets = Array.from({ length: 300 }, (_, i) => packet(100, i % 256));
    const file = oggOpus({ channels: 2, preSkip: 312, frames: 300 * 960 - 500, packets });
    const back = readOggOpus(file);
    expect(back.packets).toHaveLength(300);
    expect(back.pages).toBe(4);
    expect(pagesOf(file).map((page) => page.granule)).toEqual([0, 0, 255 * 960, 312 + 300 * 960 - 500]);
  });

  it('refuses a page whose bytes were changed', () => {
    const file = oggOpus({ channels: 2, preSkip: 312, frames: 960, packets: [packet(20, 7)] });
    file[file.length - 3] = file[file.length - 3]! ^ 0xff;
    expect(() => readOggOpus(file)).toThrow(/checksum/);
  });

  it('reads the pre-skip of a head an encoder hands out', () => {
    expect(preSkipOf(opusHead(2, 3840))).toBe(3840);
    expect(preSkipOf(new Uint8Array(19))).toBeNull();
  });
});

describe('Opus in Ogg as it comes in (#349)', () => {
  /** A CELT packet of 20 ms at full band: config 31, one frame. */
  const celt = (size: number, fill: number) => {
    const data = new Uint8Array(size).fill(fill);
    data[0] = 31 << 3;
    return { data, samples: 960 };
  };
  const file = oggOpus({
    channels: 2,
    preSkip: 312,
    frames: 300 * 960 - 312,
    packets: Array.from({ length: 300 }, (_, i) => celt(100 + (i % 300), i % 256)),
  });

  it('reads a file pushed in pieces as it reads it whole, each packet placed where it starts', () => {
    const reader = new OggOpusReader();
    for (let at = 0, size = 1; at < file.length; at += size, size = (size * 7 + 3) % 4000) {
      reader.push(file.subarray(at, at + size));
    }
    const whole = readOggOpus(file);
    expect(reader.packets.map((p) => p.data)).toEqual(whole.packets);
    expect(reader.packets.slice(0, 3).map((p) => p.at)).toEqual([0, 960, 1920]);
    expect(reader.packets.at(-1)!.at).toBe(299 * 960);
    expect([reader.channels, reader.preSkip, reader.ended]).toEqual([2, 312, true]);
  });

  it('holds a page back until all of it is there', () => {
    const reader = new OggOpusReader();
    reader.push(file.subarray(0, 4000));
    const seen = reader.packets.length;
    expect(reader.ended).toBe(false);
    reader.push(file.subarray(4000));
    expect(reader.packets.length).toBeGreaterThan(seen);
    expect(reader.packets).toHaveLength(300);
  });

  it('counts the samples of a packet from its TOC byte', () => {
    expect(opusPacketSamples(Uint8Array.of(31 << 3))).toBe(960);
    expect(opusPacketSamples(Uint8Array.of((28 << 3) | 1))).toBe(240);
    expect(opusPacketSamples(Uint8Array.of((3 << 3) | 2))).toBe(2 * 2880);
    expect(opusPacketSamples(Uint8Array.of((13 << 3) | 3, 3))).toBe(3 * 960);
    expect(opusPacketSamples(Uint8Array.of(12 << 3))).toBe(480);
    expect(opusPacketSamples(new Uint8Array(0))).toBe(0);
  });
});