I made two tutorial videos this week: one is Ep27, which is live, and another that’s still scheduled. The pipeline is the same for both — record the narration, convert it to SRT, use Remotion to lock the animation to the subtitle timing, then stitch and normalize with ffmpeg. This post only covers the production-side stuff I kept getting corrected on, the kind of thing I want to get right the first time next round.
Subtitles Aren’t Pasted In Line by Line
The first thing I kept getting corrected on: this is not subtitle animation. Putting one card on screen for every line of narration breaks the restraint principle. The right approach is to keep only the key point — one heading plus at most two supporting elements. Once you cut to that density, the screen stops getting packed with text one narration line at a time.
Match the Font Size to the Slide Spec
The second one is font size. Remotion defaults to roughly 28-32, and that’s too small to read on a phone. I switched to matching the slide spec: body is 2.4rem, about 38, and the video actually used 40.
After You Cut Content, Re-check the Timing Anchors
The third one is the easiest to miss: after trimming, you have to re-check the timing anchors. The bug came from cutting content but leaving the old fadeIn anchors behind, which makes the animation fire ahead of the narration. In Ep27 there was a spot where the S10e chips were still anchored to an email section I’d already cut, so they came in a full 14 seconds early.
The most effective way to catch this is to fan out several subagents to audit in segments, checking each entrance one by one: for every global = sceneStart + X, which SRT line does it actually land on? Ep27 ended up with three fixes where the animation ran ahead of the narration (S1, S10e, S11a).
Remotion Crashes on Videos Over 10 Minutes With a Video Component
When the video runs over 10 minutes and the composition contains a Video component, Remotion’s render crashes with ffmpeg 254.
My workaround was to split the whole thing apart: the final cut uses a demo prop to exclude the screen recording, so Remotion only renders the intro animation segment (--frames=0-10601), and the screen recording gets stitched in separately with ffmpeg concat. That way Remotion never has to handle an over-long clip and a Video component in a single render.
Normalizing Quiet Narration: Three Pitfalls
The intro narration on the other video was recorded extremely quiet — integrated came out at −39 LUFS, with peaks only at −19 dBFS. Pulling that up to −13 means +26dB, and that much gain alone buried three pitfalls.
Pitfall one: loudnorm linear=true only applies linear gain and won’t engage the true-peak limiter, so peaks shot up to +1.2 dBTP.
Pitfall two: pushing the full 26dB through loudnorm in one pass clips. That’s outside its design range, and even dynamic mode hit +2 dBTP.
Pitfall three: alimiter defaults to level=true, which automatically pulls the level back up to full scale, canceling out the limiting you just did. You have to set it to level=false.
The fix was to skip loudnorm entirely and use volume=29dB,alimiter=level=false:limit=0.63.
opencc s2twp Over-Localization
For converting the narration from Simplified to Traditional Chinese I use opencc s2twp, and it over-localizes. It turns 荧幕 into 熒幕 when it should be 螢幕, and 权限 into 許可權 when it should be 權限. Always grep the subtitles for those two words after converting.
Those are the production-side things two videos kept correcting me on this week. The finished Ep27 is here: https://youtu.be/9nQe9OYYhP4.