DPL Digital-HD (DHD) Performance Testing & Certification Program DPL Labs provides technical performance testing services for Digital-HD (DHD) products. In 2007 we introduced the first independent Digital-HD (DHD) performance testing and certification program where DPL Member Companies submit their products for evaluation. Successful products are granted the DPL Seal of Approval which signifies high performance and reliability. Today that program has been expanded to include Full 4K Product Certification. Only the Best Pass the Test.