Bitmovin evaluated different segment lengths for adaptive bitrate streaming to determine the optimal length. They found that lengths under 2 seconds performed poorly for encoding efficiency. Lengths of 4 seconds and above had similar performance but shorter lengths hindered streaming performance over HTTP/1.0. Their tests showed 6 second segments performed well over both HTTP/1.0 and HTTP/1.1. Therefore, Bitmovin recommends using variable lengths around 4 seconds on average to balance encoding efficiency and adaptive streaming performance.