public com.google.protobuf.ByteString getMarkupBytes() {
    java.lang.Object ref = "";
    if (inputSourceCase_ == 5) {
      ref = inputSource_;
    }
    if (ref instanceof java.lang.String) {
      com.google.protobuf.ByteString b =
          com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
      if (inputSourceCase_ == 5) {
        inputSource_ = b;
      }
      return b;
    } else {
      return (com.google.protobuf.ByteString) ref;
    }
  }
<pre>
Markup for HD voices specifically. This field may not be used with any
other voices.
</pre>

<code>string markup = 5;</code>

@return The bytes for markup.
java-texttospeech/proto-google-cloud-texttospeech-v1/src/main/java/com/google/cloud/texttospeech/v1/SynthesisInput.java