Update audioStartTime and audioEndTime to be relative to start of aud… - #203
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alan33d wants to merge 4 commits into
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Update audioStartTime and audioEndTime to be relative to start of aud…#203alan33d wants to merge 4 commits into
alan33d wants to merge 4 commits into
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…io stream We want to switch to stream-Relative (0-based) impl. since: - In Web Audio and Media APIs (HTMLMediaElement.currentTime, AudioContext.currentTime, WebCodecs VideoFrame.timestamp), media timelines are always 0-based offsets relative to stream start, not the time origin. - Immune to inter-process jitter since SODA and audio capture run in a separate utility/browser process. Translating stream offsets to the renderer's timeOrigin relies on estimating when IPC AudioStarted() arrived, which introduces IPC latency jitter. Stream-relative offsets are not prune to this and aligns with the raw audio frames. - If SpeechRecognition is used with a pre-recorded MediaStreamTrack, a 0-based stream offset reflects the actual position in the audio track regardless of when the webpage was loaded. - Being relative to performance.timeOrigin doesn't make sense in general for the Web Speech API because it assumes that the audio source is live. Since a SpeechRecognizer can also be created for a prerecorded media stream I think the timestamps on the speech recognition events should be relative to the position in that media stream. See https://crbug.com/542330168 for more details.
Added a section on converting stream timestamps to document time origin and provided a live translation latency example with code.
reillyeon
approved these changes
Aug 12, 2026
Added separator before security section and closed example section for live transcription measurements.
michaelwasserman
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michaelwasserman
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Drive by review: lgtm with a nit, fwiw. I implemented the suggested timestamp offsetting in my demo, and it seems to work well. https://michaelwasserman.github.io/web-speech-demos/speech_latency.html
alan33d
marked this pull request as ready for review
August 13, 2026 00:19
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We want to switch to stream-Relative (0-based) impl. since:
See https://crbug.com/542330168 for more details.