@webav/av-recorder/dist/av-recorder.js

Record MediaStream to MP4, Use Webcodecs API encode VideoFrame and AudioData, [mp4box.js](https://github.com/gpac/mp4box.js) as muxer. 录制 MediaStream 到 MP4，使用 Webcodecs API 编码 VideoFrame、AudioData，mp4box.js 封装。

import { EventTool as V, Log as w, recodemux as k, autoReadStream as p, file2stream as A } from "@webav/internal-utils";
class P {
  #e = "inactive";
  get state() {
    return this.#e;
  }
  set state(e) {
    throw new Error("state is readonly");
  }
  #s = new V();
  on = this.#s.on;
  #o;
  #t;
  constructor(e, t = {}) {
    this.#o = C(e, t), this.#t = new b(this.#o.video.expectFPS);
  }
  #r = () => {
  };
  /**
   * 开始录制，返回 MP4 文件流
   * @param timeSlice 控制流输出数据的时间间隔，单位毫秒
   *
   */
  start(e = 500) {
    if (this.#e === "stopped") throw Error("AVRecorder is stopped");
    w.info("AVRecorder.start recoding");
    const { streams: t } = this.#o;
    if (t.audio == null && t.video == null)
      throw new Error("No available tracks in MediaStream");
    const { stream: o, exit: i } = x(
      { timeSlice: e, ...this.#o },
      this.#t,
      () => {
        this.stop();
      }
    );
    return this.#r(), this.#r = i, o;
  }
  /**
   * 暂停录制
   */
  pause() {
    this.#e = "paused", this.#t.pause(), this.#s.emit("stateChange", this.#e);
  }
  /**
   * 恢复录制
   */
  resume() {
    if (this.#e === "stopped") throw Error("AVRecorder is stopped");
    this.#e = "recording", this.#t.play(), this.#s.emit("stateChange", this.#e);
  }
  /**
   * 停止
   */
  async stop() {
    this.#e !== "stopped" && (this.#e = "stopped", this.#r());
  }
}
function C(s, e) {
  const t = {
    bitrate: 3e6,
    expectFPS: 30,
    videoCodec: "avc1.42E032",
    ...e
  }, { streams: o, width: i, height: c, sampleRate: d, channelCount: n } = R(s);
  return {
    video: {
      width: i ?? 1280,
      height: c ?? 720,
      expectFPS: t.expectFPS,
      codec: t.videoCodec
    },
    audio: {
      codec: "aac",
      sampleRate: d ?? 44100,
      channelCount: n ?? 2
    },
    bitrate: t.bitrate,
    streams: o
  };
}
function R(s) {
  const e = s.getVideoTracks()[0], t = { streams: {} };
  e != null && (Object.assign(t, e.getSettings()), t.streams.video = new MediaStreamTrackProcessor({
    track: e
  }).readable);
  const o = s.getAudioTracks()[0];
  return o != null && (Object.assign(t, o.getSettings()), w.info("AVRecorder recording audioConf:", t), t.streams.audio = new MediaStreamTrackProcessor({
    track: o
  }).readable), t;
}
class b {
  constructor(e) {
    this.expectFPS = e, this.#i = Math.floor(e * 3);
  }
  // 当前帧的偏移时间，用于计算帧的 timestamp
  #e = performance.now();
  // 编码上一帧的时间，用于计算出当前帧的持续时长
  #s = this.#e;
  // 用于限制 帧率
  #o = 0;
  // 如果为true，则暂停编码数据
  // 取消暂停时，需要减去
  #t = !1;
  // 触发暂停的时间，用于计算暂停持续了多久
  #r = 0;
  // 间隔多少帧生成一个关键帧
  #i = 30;
  start() {
    this.#e = performance.now(), this.#s = this.#e;
  }
  play() {
    this.#t && (this.#t = !1, this.#e += performance.now() - this.#r, this.#s += performance.now() - this.#r);
  }
  pause() {
    this.#t || (this.#t = !0, this.#r = performance.now());
  }
  transfromVideo(e) {
    const t = performance.now(), o = t - this.#e;
    if (this.#t || // 避免帧率超出期望太高
    this.#o / o * 1e3 > this.expectFPS) {
      e.close();
      return;
    }
    const i = new VideoFrame(e, {
      // timestamp 单位 微秒
      timestamp: o * 1e3,
      duration: (t - this.#s) * 1e3
    });
    return this.#s = t, this.#o += 1, e.close(), {
      vf: i,
      opts: { keyFrame: this.#o % this.#i === 0 }
    };
  }
  transformAudio(e) {
    if (this.#t) {
      e.close();
      return;
    }
    return e;
  }
}
function x(s, e, t) {
  let o = null, i = null;
  const [c, d] = [
    s.streams.video != null,
    s.streams.audio != null && s.audio != null
  ], n = k({
    video: c ? { ...s.video, bitrate: s.bitrate ?? 3e6 } : null,
    audio: d ? s.audio : null
  });
  let u = !1;
  if (c) {
    let r = null, l = 0;
    const f = (a) => {
      clearTimeout(l), r?.close(), r = a;
      const h = e.transfromVideo(a.clone());
      h != null && (n.encodeVideo(h.vf, h.opts), l = self.setTimeout(() => {
        if (r == null) return;
        const S = new VideoFrame(r, {
          timestamp: r.timestamp + 1e6,
          duration: 1e6
        });
        f(S);
      }, 1e3));
    };
    e.start();
    const T = p(s.streams.video, {
      onChunk: async (a) => {
        if (u) {
          a.close();
          return;
        }
        f(a);
      },
      onDone: () => {
      }
    });
    o = () => {
      T(), clearTimeout(l), r?.close();
    };
  }
  d && (i = p(s.streams.audio, {
    onChunk: async (r) => {
      if (u) {
        r.close();
        return;
      }
      e.transformAudio(r) != null && n.encodeAudio(r);
    },
    onDone: () => {
    }
  }));
  const { stream: g, stop: v } = A(
    n.mp4file,
    s.timeSlice,
    () => {
      m(), t();
    }
  );
  function m() {
    u = !0, o?.(), i?.(), n.close(), v();
  }
  return { exit: m, stream: g };
}
export {
  P as AVRecorder
};
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