example: 添加 sei 的使用示例

examples/sei.ts

@@ -0,0 +1,112 @@
+
+import AVStream from 'avformat/AVStream'
+import { AVCodecID } from 'avutil/codec'
+import BufferReader from 'common/io/BufferReader'
+import AVPacket, { AVPacketFlags } from 'avutil/struct/avpacket'
+
+import { avMalloc } from 'avutil/util/mem'
+import { mapUint8Array } from 'cheap/std/memory'
+import { addAVPacketData, getAVPacketData } from 'avutil/util/avpacket'
+
+import * as hevc from 'avformat/codecs/hevc'
+import * as h264 from 'avformat/codecs/h264'
+import * as naluUtil from 'avutil/util/nalu'
+
+export async function readSEI(avpacket: pointer<AVPacket>, stream: AVStream) {
+
+  function readSEINumber(bufferReader: BufferReader) {
+    let value = 0
+    let now = bufferReader.readUint8()
+    while (now === 0xff) {
+      value += 0xff
+      now = bufferReader.readUint8()
+    }
+    value += now
+
+    return value
+  }
+
+  if ((avpacket.flags & AVPacketFlags.AV_PKT_FLAG_KEY)
+    && (
+      stream.codecpar.codecId === AVCodecID.AV_CODEC_ID_H264
+        || stream.codecpar.codecId === AVCodecID.AV_CODEC_ID_HEVC
+    )
+  ) {
+    const nalus = avpacket.bitFormat === h264.BitFormat.ANNEXB
+      ? naluUtil.splitNaluByStartCode(getAVPacketData(avpacket))
+      : naluUtil.splitNaluByLength(getAVPacketData(avpacket), stream.metadata.naluLengthSizeMinusOne || 3)
+
+    if (stream.codecpar.codecId === AVCodecID.AV_CODEC_ID_H264) {
+      nalus.forEach((nalu) => {
+        const type = nalu[0] & 0x1f
+        if (type === h264.H264NaluType.kSliceSEI) {
+          const bufferReader = new BufferReader(nalu.subarray(1))
+          const payloadType = readSEINumber(bufferReader)
+          const payloadSize = readSEINumber(bufferReader)
+          const payload = bufferReader.readBuffer(payloadSize)
+          console.log(`receive sei, payloadType: ${payloadType}, payloadSize: ${payloadSize}`)
+        }
+      })
+    }
+    else if (stream.codecpar.codecId === AVCodecID.AV_CODEC_ID_HEVC) {
+      nalus.forEach((nalu) => {
+        const type = (nalu[0] >>> 1) & 0x3f
+        if (type === hevc.HEVCNaluType.kSliceSEI_PREFIX || hevc.HEVCNaluType.kSliceSEI_SUFFIX) {
+          const bufferReader = new BufferReader(nalu.subarray(1))
+          const payloadType = readSEINumber(bufferReader)
+          const payloadSize = readSEINumber(bufferReader)
+          const payload = bufferReader.readBuffer(payloadSize)
+          console.log(`receive sei, payloadType: ${payloadType}, payloadSize: ${payloadSize}`)
+        }
+      })
+    }
+  }
+}
+
+// h264 for example
+export async function writeSEI(avpacket: pointer<AVPacket>, stream: AVStream, payloadType: number, payload: Uint8Array) {
+  const nalus = avpacket.bitFormat === h264.BitFormat.ANNEXB
+    ? naluUtil.splitNaluByStartCode(getAVPacketData(avpacket))
+    : naluUtil.splitNaluByLength(getAVPacketData(avpacket), stream.metadata.naluLengthSizeMinusOne || 3)
+
+  function pushSEINumber(header: number[], value: number) {
+    const count = (value / 255) | 0
+    const end = value % 255
+    for (let i = 0; i < count; i++) {
+      header.push(255)
+    }
+    header.push(end)
+  }
+
+  const header: number[] = [h264.H264NaluType.kSliceSEI]
+  pushSEINumber(header, payloadType)
+  pushSEINumber(header, payload.length)
+  const sei = new Uint8Array(header.length + payload.byteLength)
+  sei.set(header, 0)
+  sei.set(new Uint8Array(payload), header.length)
+
+  const type = nalus[0][0] & 0x1f
+
+  if (type === h264.H264NaluType.kSliceAUD) {
+    nalus.splice(1, 0, sei)
+  }
+  else {
+    nalus.unshift(sei)
+  }
+
+  let length = avpacket.bitFormat === h264.BitFormat.ANNEXB
+    ? nalus.reduce((prev, nalu, index) => {
+      return prev + (index ? 3 : 4) + nalu.length
+    }, 0)
+    : nalus.reduce((prev, nalu) => {
+      return prev + (stream.metadata.naluLengthSizeMinusOne || 3) + 1 + nalu.length
+    }, 0)
+
+  const data = avMalloc(length)
+
+  avpacket.bitFormat === h264.BitFormat.ANNEXB
+    ? naluUtil.joinNaluByStartCode(nalus, mapUint8Array(data, length))
+    : naluUtil.joinNaluByLength(nalus, stream.metadata.naluLengthSizeMinusOne || 3, mapUint8Array(data, length))
+
+  addAVPacketData(avpacket, data, length)
+}