feat: 新增 webvtt 解码器

src/avcodec/subtitle/SubtitleDecoder.ts

@@ -0,0 +1,128 @@
+/*
+ * libmedia wasm audio decoder
+ *
+ * 版权所有 (C) 2024 赵高兴
+ * Copyright (C) 2024 Gaoxing Zhao
+ *
+ * 此文件是 libmedia 的一部分
+ * This file is part of libmedia.
+ * 
+ * libmedia 是自由软件；您可以根据 GNU Lesser General Public License（GNU LGPL）3.1
+ * 或任何其更新的版本条款重新分发或修改它
+ * libmedia is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3.1 of the License, or (at your option) any later version.
+ * 
+ * libmedia 希望能够为您提供帮助，但不提供任何明示或暗示的担保，包括但不限于适销性或特定用途的保证
+ * 您应自行承担使用 libmedia 的风险，并且需要遵守 GNU Lesser General Public License 中的条款和条件。
+ * libmedia is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ */
+
+import AVCodecParameters from 'avutil/struct/avcodecparameters'
+import AVPacket from 'avutil/struct/avpacket'
+import AVFrame, { AVFramePool, AVFrameRef } from 'avutil/struct/avframe'
+import { createAVFrame, destroyAVFrame } from 'avutil/util/avframe'
+import Decoder from './decoder/Decoder'
+import { AVCodecID } from 'avutil/codec'
+import * as errorType from 'avutil/error'
+import WebVvtDecoder from './decoder/WebVttDecoder'
+
+export type SubtitleDecoderOptions = {
+  onReceiveFrame?: (frame: pointer<AVFrame>) => void
+  onError?: (error?: Error) => void
+  avframePool?: AVFramePool
+}
+
+export default class SubtitleDecoder {
+
+  private options: SubtitleDecoderOptions
+
+  private frame: pointer<AVFrame>
+
+  private decoder: Decoder
+
+  constructor(options: SubtitleDecoderOptions) {
+    this.options = options
+  }
+
+  private getAVFrame() {
+    if (this.frame) {
+      return this.frame
+    }
+    return this.frame = this.options.avframePool ? this.options.avframePool.alloc() : createAVFrame()
+  }
+
+  private outputAVFrame() {
+    if (this.frame) {
+      if (this.options.onReceiveFrame) {
+        this.options.onReceiveFrame(this.frame)
+      }
+      else {
+        this.options.avframePool ? this.options.avframePool.release(this.frame as pointer<AVFrameRef>) : destroyAVFrame(this.frame)
+      }
+
+      this.frame = nullptr
+    }
+  }
+
+  private receiveAVFrame() {
+    return this.decoder.receiveAVFrame(this.getAVFrame())
+  }
+
+  public async open(parameters: pointer<AVCodecParameters>) {
+    switch (parameters.codecId) {
+      case AVCodecID.AV_CODEC_ID_WEBVTT:
+        this.decoder = new WebVvtDecoder()
+        break
+      default:
+        return errorType.CODEC_NOT_SUPPORT
+    }
+    return 0
+  }
+
+  public decode(avpacket: pointer<AVPacket>) {
+    let ret = this.decoder.sendAVPacket(avpacket)
+
+    if (ret) {
+      return ret
+    }
+
+    while (true) {
+      ret = this.receiveAVFrame()
+      if (ret === 1) {
+        this.outputAVFrame()
+      }
+      else if (ret < 0) {
+        return ret
+      }
+      else {
+        break
+      }
+    }
+
+    return 0
+  }
+
+  public async flush() {
+    this.decoder.flush()
+    while (1) {
+      const ret = this.receiveAVFrame()
+      if (ret < 1) {
+        return
+      }
+      this.outputAVFrame()
+    }
+  }
+
+  public close() {
+    if (this.frame) {
+      this.options.avframePool ? this.options.avframePool.release(this.frame as pointer<AVFrameRef>) : destroyAVFrame(this.frame)
+      this.frame = nullptr
+    }
+  }
+}

src/avcodec/subtitle/decoder/Decoder.ts

@@ -0,0 +1,8 @@
+import AVFrame from 'avutil/struct/avframe';
+import AVPacket from 'avutil/struct/avpacket'
+
+export default abstract class Decoder {
+  public abstract sendAVPacket(avpacket: pointer<AVPacket>): int32
+  public abstract receiveAVFrame(avframe: pointer<AVFrame>): int32
+  public abstract flush(): int32
+}

src/avcodec/subtitle/decoder/WebVttDecoder.ts

@@ -0,0 +1,156 @@
+/*
+ * libmedia vtt decode
+ *
+ * 版权所有 (C) 2024 赵高兴
+ * Copyright (C) 2024 Gaoxing Zhao
+ *
+ * 此文件是 libmedia 的一部分
+ * This file is part of libmedia.
+ * 
+ * libmedia 是自由软件；您可以根据 GNU Lesser General Public License（GNU LGPL）3.1
+ * 或任何其更新的版本条款重新分发或修改它
+ * libmedia is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3.1 of the License, or (at your option) any later version.
+ * 
+ * libmedia 希望能够为您提供帮助，但不提供任何明示或暗示的担保，包括但不限于适销性或特定用途的保证
+ * 您应自行承担使用 libmedia 的风险，并且需要遵守 GNU Lesser General Public License 中的条款和条件。
+ * libmedia is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ */
+
+import AVFrame from 'avutil/struct/avframe'
+import AVPacket from 'avutil/struct/avpacket'
+import Decoder from './Decoder'
+import * as text from 'common/util/text'
+import { getAVPacketData } from 'avutil/util/avpacket'
+import { avbufferAlloc } from 'avutil/util/avbuffer'
+import { memcpyFromUint8Array } from 'cheap/std/memory'
+import { Rational } from 'avutil/struct/rational'
+
+function formatTime(time: string) {
+  time = time.trim()
+  let list = time.split(':')
+
+  let ts = 0n
+
+  if (list.length === 3) {
+    ts += BigInt(+(list.shift().trim())) * 3600000n
+  }
+  ts += BigInt(+(list.shift().trim())) * 60000n
+
+  list = list.shift().trim().split('.')
+  ts += BigInt(+(list.shift().trim())) * 1000n
+  ts += BigInt(+(list.shift().trim()))
+
+  return ts
+}
+
+export default class WebVvtDecoder extends Decoder {
+
+  private queue: {
+    pts: int64
+    duration: int64
+    context: string
+    timeBase: Rational
+  }[]
+
+  constructor() {
+    super()
+  }
+
+  private findTimelineTag(constant: string) {
+    const start = constant.indexOf('<')
+    if (start >= 0) {
+      const end = constant.indexOf('>', start)
+      if (end > start) {
+        if (/^(\d{2,}:)?\d{2}:\d{2}\.\d{1,3}$/.test(constant.substring(start + 1, end))) {
+          return {
+            start,
+            end
+          }
+        }
+      }
+    }
+    return {
+      start: -1,
+      end: -1,
+    }
+  }
+
+  public sendAVPacket(avpacket: pointer<AVPacket>): int32 {
+    let context = text.decode(getAVPacketData(avpacket))
+    let startPts = avpacket.pts
+    const endPts = startPts + avpacket.duration
+
+    const cache: string[] = []
+
+    while (true) {
+      const { start, end } = this.findTimelineTag(context)
+      if (start < 0) {
+        break
+      }
+      const pts = formatTime(context.substring(start + 1, end))
+
+      cache.push(context.substring(0, start))
+
+      this.queue.push({
+        context: cache.join(''),
+        pts: startPts,
+        duration: pts - startPts,
+        timeBase: {
+          den: avpacket.timeBase.den,
+          num: avpacket.timeBase.num
+        }
+      })
+
+      startPts = pts
+      context = context.substring(end + 1)
+    }
+
+    cache.push(context)
+
+    this.queue.push({
+      context: cache.join(''),
+      pts: startPts,
+      duration: endPts - startPts,
+      timeBase: {
+        den: avpacket.timeBase.den,
+        num: avpacket.timeBase.num
+      }
+    })
+
+    return 0
+  }
+
+  public receiveAVFrame(avframe: pointer<AVFrame>): int32 {
+    if (this.queue.length) {
+      const item = this.queue.shift()
+      avframe.pts = item.pts
+      avframe.duration = item.duration
+
+      const buffer = text.encode(item.context)
+
+      const ref = avbufferAlloc(buffer.length)
+
+      memcpyFromUint8Array(ref.data, buffer.length, buffer)
+
+      avframe.buf[0] = ref
+      avframe.data[0] = ref.data
+      avframe.linesize[0] = buffer.length
+      avframe.timeBase.den = item.timeBase.den
+      avframe.timeBase.num = item.timeBase.num
+
+      return 1
+    }
+    return 0
+  }
+
+  public flush(): int32 {
+    return 0
+  }
+}