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Diffstat (limited to 'docs/MESHBAY_DESIGN.md')
| -rw-r--r-- | docs/MESHBAY_DESIGN.md | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/docs/MESHBAY_DESIGN.md b/docs/MESHBAY_DESIGN.md index 7ce1168..8f91a87 100644 --- a/docs/MESHBAY_DESIGN.md +++ b/docs/MESHBAY_DESIGN.md @@ -2052,14 +2052,19 @@ MSE string) fed to a source buffer, with the node holding one slot per viewer. from the end and echoed back; the client supplies the timestamp offset, because copying timestamps does not preserve position. - **`stream_init.start` names where the picture begins, never where the viewer - dragged.** Copied video can only begin on a keyframe, so on that path the node - resolves the request to the keyframe at or before it, seeks to that, and reports - that. The client builds `SourceBuffer.timestampOffset` out of this number, and a - subtitle cue carries the source's own absolute time: one GOP of disagreement - between the two puts every line on screen before it is spoken. The look-up is a - bounded read of the thirty seconds before the request, measured at 0.12–0.51 s - on a real title, and only the copy path needs it — re-encoded video begins - exactly where it is asked to. + dragged**, and on the copy path that position is **measured, never predicted**. + The client builds `SourceBuffer.timestampOffset` out of this number and a + subtitle cue carries the source's own absolute time, so every second of + disagreement puts a line on screen a second away from the voice saying it. + Reading the key frames and taking the last one at or before the request answers + a different question twice over: Matroska's Cues index only some keyframes, so + an index seek backs off to an indexed one that can be much earlier, and the + landing point moves with **which streams are mapped**, because the container is + positioned where every mapped stream has data — one real seek answered 4909.863 s + from the frame list and delivered 4907.236 s. So the node runs the same seek with + the same mapping, copies one frame under `-copyts`, and reads the answer back: + 0.06–0.07 s, cheaper than the scan it replaced. Only the copy path needs it — + re-encoded video begins exactly where it is asked to. - **A seek trims what it can, and what it can differs per stream — which is a desync, not an inconvenience.** Accurate seeking cannot trim copied video, which must begin on a keyframe, but it does trim re-encoded audio to the exact request. |