# ECP-0114: Live Playback Audio Stability

Status: Draft

## Problem / context

Local HDHomeRun playback can sound choppy even while video continues. The current desktop bridge starts a full three-rung CMAF/HLS ladder for local watching, and each variant carries its own AAC encode. OTA MPEG-TS timestamps can also jitter enough that straight AAC transcoding preserves audible gaps or corrections.

## Decision

Use a playback-specific encoding profile for local watching:

- local desktop playback encodes only the 720p rendition instead of the full ABR ladder;
- all live AAC transcode paths force AAC-LC stereo and resample with timestamp compensation;
- keep the full multi-variant ladder for publishing and sharing paths.

## Consequences

- Local watching spends less CPU and avoids variant-switch audio discontinuities.
- AAC output gets a continuous 48 kHz stereo timeline even when OTA timestamps jitter.
- Published streams remain multi-variant and manifest-compatible.

## Alternatives Considered

- Keep full ABR for local playback. Rejected because the local player does not need ABR to watch a LAN tuner and the separate AAC timelines make audible switching more likely.
- Fix only the player buffer. Rejected because the source fragments should already have stable audio timestamps before they reach HLS or MSE.

## Rollout / teardown

Remove the playback-specific variant selection and the audio resample filter from the ffmpeg profiles.