30 lines
1.4 KiB
Markdown
30 lines
1.4 KiB
Markdown
# ECP-0114: Live Playback Audio Stability
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Status: Draft
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## Problem / context
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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.
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## Decision
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Use a playback-specific encoding profile for local watching:
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- local desktop playback encodes only the 720p rendition instead of the full ABR ladder;
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- all live AAC transcode paths force AAC-LC stereo and resample with timestamp compensation;
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- keep the full multi-variant ladder for publishing and sharing paths.
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## Consequences
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- Local watching spends less CPU and avoids variant-switch audio discontinuities.
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- AAC output gets a continuous 48 kHz stereo timeline even when OTA timestamps jitter.
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- Published streams remain multi-variant and manifest-compatible.
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## Alternatives Considered
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- 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.
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- Fix only the player buffer. Rejected because the source fragments should already have stable audio timestamps before they reach HLS or MSE.
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## Rollout / teardown
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Remove the playback-specific variant selection and the audio resample filter from the ffmpeg profiles.
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