Gradual decoder refresh (GDR) helps the decoder refresh or start decoding without a full Intra-Frame. In GDR mode, the encoder inserts intra-encoded MB strips (horizontal or vertical) into inter frames. This additional data allows for decoders to refresh, enabling the decode of compressed streams even after streams have already started or are recovering from streams due to unreliable network conditions.
For more information, see GDR Intra Refresh in H.264/H.265 Video Codec Unit LogiCORE IP Product Guide (PG252).