public Builder setInputKey(java.lang.String value) {
        if (value == null) {
          throw new NullPointerException();
        }
        inputKey_ = value;
        bitField0_ |= 0x00000001;
        onChanged();
        return this;
      }
<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>

@param value The inputKey to set.
@return This builder for chaining.
java-video-live-stream/proto-google-cloud-live-stream-v1/src/main/java/com/google/cloud/video/livestream/v1/AudioStream.java