@java.lang.Override
    public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
      if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(atomKey_)) {
        com.google.protobuf.GeneratedMessageV3.writeString(output, 1, atomKey_);
      }
      if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(inputKey_)) {
        com.google.protobuf.GeneratedMessageV3.writeString(output, 2, inputKey_);
      }
      if (inputTrack_ != 0) {
        output.writeInt32(3, inputTrack_);
      }
      getUnknownFields().writeTo(output);
    }
<pre>
Required. The zero-based index of the track in the input file.
</pre>

<code>int32 input_track = 3 [(.google.api.field_behavior) = REQUIRED];</code>

@return The inputTrack.
java-video-transcoder/proto-google-cloud-video-transcoder-v1/src/main/java/com/google/cloud/video/transcoder/v1/TextStream.java