The 8977AP-4U is a compact, high-performance, high-density digital audio processor. It provides processing at channel level for up to eight PCM audio channels. It also provides sample-rate conversion and synchronization for asynchronous and consumer-type sources. Automatic delay tracking synchronizes the sound to a video synchronizer, while a user-configurable delay can compensate for fixed latency processing.

A particularly powerful feature of the 8977AP-4U is its ability to handle Dolby E streams. These can be both routed and delayed while preserving the non-PCM data. The 8977AP-4U can handle a mix of Dolby E streams and PCM channels so that, for example, a Dolby stream on AES input 1 can be routed to AES output 2 and then replaced by selected PCM channels on output 1. Audio input and output connectors are unbalanced (see 8977AP-4B for balanced connectors).

PCM audio can be synchronized to a reference; either a color black video reference, tri-level syncs, an AES feed, or even word-clock can be used. Reference can be fed directly to the module by fitting the optional 8900GEN-SM reference input sub-module or alternatively taken from one of GeckoFlex's two internal busses. This allows several modules in a frame to share a reference feed including sharing it with a video synchronizer.