Wake Word Pre-Roll Overview

Definition

The following diagram illustrates the structure of a typical Alexa utterance, and defines the term "wake word pre-roll". The pre-roll audio segment is the first segment of a wake word-initiated audio utterance, preceding the wake word audio segment.

AVS Pre-Roll Streaming Requirements

AVS Streaming Requirements mandate that each AVS SpeechRecognizer request MUST provide a 500 millisecond span of pre-roll audio ahead of the wake word audio segment. Additional context is provided in the linked requirements document regarding the importance of pre-roll for optimal AVS performance, taking cloud-based wake word verification as an example.

Please read the AVS streaming requirements document linked above in full, and also note that although the document is titled "Requirements for Cloud-Based Wake Word Verification", pre-roll audio has an importance over and above just cloud-based wake word verification. Many downstream audio algorithms require or benefit from the additional pre-wake-word acoustic context that pre-roll provides, including media-induced wake suppression and automatic speech recognition. Failure to send sufficient pre-roll will degrade the AVS response to your device's requests.

More Information

See the Pre-Roll Integration section in this guide for more details.