add silence buffering

audio/utils.go

@@ -89,16 +89,29 @@ func record(length float64, silenceLen float64) chan *recordResponse {
  }
 
  // discard silence at the beginning of the recording. Why waste time with it?
+ // however, to avoid an abrupt "chopping", we want to keep some amount of silence
+
+ silenceBuf := make([]int16, 0)
+ maxLen := 16 * BufSize
+
  for {
  stream.Read()
+ // keep up to maxLen previous bytes
+ if len(silenceBuf) > maxLen {
+ silenceBuf = append(silenceBuf[:maxLen], buf...)
+ } else {
+ silenceBuf = append(silenceBuf, buf...)
+ }
+ // check silence here so that we don't have a gap of size BufSize from the audio stream
  if !isSilent(buf) {
- prch <- &recordResponse{nil, buf, nil}
  break
  }
  }
 
- // read data until the specified amount of silence or until the
- // specified amount of length
+ // send the recorded silence over to the processing function
+ prch <- &recordResponse{nil, silenceBuf, nil}
+
+ // read data until the specified amount of silence or until the specified amount of length
  dataLen := 0
  silentFor := 0.0
  for {