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The speed setting scaled the frame-sampling index (frame * speed) but left each sequence's durationInFrames unscaled, so at speed=2 the index ran past the pre-rendered frames array halfway through each typing sequence, rendering undefined (blank). Scale durationInFrames by 1/speed for non-transition sequences so the real timeline matches the content timeline, and clamp the sample index as a safety net. Transition sequences keep their fixed 20-frame slide timing. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
speedmetadata setting scaled the frame-sampling index (frame * speed) but left each sequence'sdurationInFramesunscaled, so atspeed: 2the index ran past the pre-renderedframesarray halfway through each typing sequence, returningundefinedand rendering blank frames.getCompositionData, scale each non-transition sequence'sdurationInFramesby1/speedso the real timeline matches the content timeline. Transition sequences keep their fixed 20-frame slide timing (speed is a typing-animation concept, not a transition one).frames.length - 1in the renderer as a safety net for rounding and for the un-scaled transition sequences.Fixes #26.
Test plan
npm run lint— no new warningstsc --noEmit— cleanspeed: 2— video duration halves, full typing animation plays end-to-end, no blank second halfspeed: 0.5— duration doubles, typing held longer per content frame, smoothspeed: 1— unchanged baseline🤖 Generated with Claude Code