stream_compressed

This event is an alternative for sending audio chunks of non PCM format audio. Compressed audio formats like mp4 or ogg are supported. The event payload is the following:

Audio samples in binary format
MIME type

Some example code:

path = '/test_audio.wav'
chunkSize = 1024 /* size of chunk in bytes */

const response = await fetch(path)
const blob = await response.blob()

const splitBlob = (file, chunkSize) => {
  let startPointer = 0
  let endPointer = file.size
  const cSize = Math.min(file.size, chunkSize)
  const chunks = []
  while (startPointer < endPointer) {
    let newStartPointer = startPointer + cSize;
    chunks.push(file.slice(startPointer, newStartPointer))
    startPointer = newStartPointer
  }
  return chunks
}

const blobChunks = splitBlob(blob, 1024)

for (const chunk of blobChunks) {
  socketLocal.emit('stream_compressed_audio', chunk, blob.type)
}

The response to this event is identical to the response to the stream_audio_samples event, i.e. a chronologically ordered sequence of recognition and partial_recognition events.

For Web environments according to the type of generated chunks stream_audio_samples should use ScriptProcessorNode and stream_compressed_audio should use MediaRecorder. Experiments show that MediaRecorder is preferred because it produces much less audio distortion.