/**
  * Sends a keyframe request to the endpoints specified in {@code endpointIds}
  *
  * @param endpointIds the list of IDs of endpoints to which to send a request for a keyframe.
  */
 private void askForKeyframes(List<String> endpointIds) {
   // TODO: Execute asynchronously.
   if (endpointIds != null && !endpointIds.isEmpty()) {
     channel.getContent().askForKeyframesById(endpointIds);
   }
 }