public Builder setGopDuration(com.google.protobuf.Duration.Builder builderForValue) {
        if (gopDurationBuilder_ == null) {
          gopMode_ = builderForValue.build();
          onChanged();
        } else {
          gopDurationBuilder_.setMessage(builderForValue.build());
        }
        gopModeCase_ = 10;
        return this;
      }
<pre>
Select the GOP size based on the specified duration. The default is
`3s`. Note that `gopDuration` must be less than or equal to
[`segmentDuration`](#SegmentSettings), and
[`segmentDuration`](#SegmentSettings) must be divisible by
`gopDuration`.
</pre>

<code>.google.protobuf.Duration gop_duration = 10;</code>
java-video-transcoder/proto-google-cloud-video-transcoder-v1/src/main/java/com/google/cloud/video/transcoder/v1/VideoStream.java