Eliminating the Downlink Stall Was More Important Than Tuning Tone

A clean frequency response is irrelevant if the playback path periodically stops feeding samples.

The acceptance condition for Eliminating the Downlink Stall Was More Important Than Tuning Tone only became clear after the system was split into boundaries. The V115 quiet AB work first focused on eliminating downlink stalls and measuring slow I2S writes before chasing smaller tonal issues.

Long-call logs showed slow writes at roughly 0.02 percent while the major stall behavior disappeared. That gave the team a stable transport/playout baseline and narrowed the remaining artifacts to shorter bursts and conversion quality. It was a better place to optimize than a path that still stopped unpredictably.

The design became clearer when configuration, runtime state and recovery behaviour were specified separately instead of being implied by implementation details. Evidence marker: v115-downlink-stall.

Fix discontinuities before polishing sound. Reliability changes what later measurements mean. Once that contract is written down, firmware and server changes can be reviewed against the same expectation instead of relying on memory.

Project evidence

LOUP engineering marker: v115-downlink-stall. This note records the design or debugging lesson without publishing device credentials, private keys, customer data or manufacturing secrets.