@java.lang.Override
    public com.google.protobuf.ByteString getInputKeyBytes() {
      java.lang.Object ref = inputKey_;
      if (ref instanceof java.lang.String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        inputKey_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
Required. The `Channel`
[InputAttachment.key][google.cloud.video.livestream.v1.InputAttachment.key]
that identifies the input that this audio mapping applies to. If an
active input doesn't have an audio mapping, the primary audio track in
the input stream will be selected.
</pre>

<code>string input_key = 6 [(.google.api.field_behavior) = REQUIRED];</code>

@return The bytes for inputKey.
java-video-live-stream/proto-google-cloud-live-stream-v1/src/main/java/com/google/cloud/video/livestream/v1/AudioStream.java