Nine video production bugs I hit in April 2026

Our channel’s production pipeline runs almost entirely on code: Remotion for animation, ffmpeg for post-production compositing, SiliconFlow ASR for subtitles, yt-dlp for downloading source material, YouTube Data API for automated uploads. When it works, a video goes from script to published with no manual steps. When it breaks, you get this post.

Nine bugs from April, in order.

1. YouTube Analytics API dimension names don’t match the Studio UI

The insightTrafficSourceType values the API returns don’t line up with what you see in Studio. “Subscribers” in the UI becomes SUBSCRIBER in the API; “Channel page” might come back as YT_CHANNEL_PAGE. Easy to get confused when you’re trying to match numbers.

On top of that, Analytics API has a 48–72 hour delay. If you run a script right after upload and see low numbers, it’s not a bug — the data just hasn’t arrived yet.

Quick check to see actual dimension values:

curl "https://youtubeanalytics.googleapis.com/v2/reports?ids=channel==MINE&metrics=views&dimensions=insightTrafficSourceType&startDate=2026-04-01&endDate=2026-04-30&key=$YT_KEY"

2. ffmpeg drawbox without timestamps causes overlapping boxes

I wanted static annotation boxes that appear during specific segments. Used drawbox filter, but put multiple boxes into a single filter_complex without separate enable='between(t,start,end)' params. Result: boxes showed up at wrong times and overlapped in strange ways.

Fix: give each box its own drawbox with its own time range.

ffmpeg -i input.mp4 \
  -vf "drawbox=x=10:y=10:w=200:h=50:color=red@0.5:enable='between(t,2,5)', \
       drawbox=x=10:y=80:w=200:h=50:color=blue@0.5:enable='between(t,8,12)'" \
  output.mp4

3. Remotion outputs yuvj420p — YouTube reads it wrong

Remotion’s default pixel format is yuvj420p (full-range). YouTube’s pipeline treats it as yuv420p (limited-range), which makes colors look washed out and too bright.

Add a transcode step after render:

ffmpeg -i remotion_output.mp4 -c:v libx264 -pix_fmt yuv420p -c:a copy final.mp4

While you’re at it, run LUFS normalization in this step too (-13 LUFS is YouTube’s target).

4. ffmpeg aselect with 200+ between() expressions OOMs

Wanted to cut 218 segments out of an audio file in one go:

ffmpeg -i input.mp3 -af "aselect='between(t,0.5,1.2)+between(t,3.1,3.8)+...'" output.mp3

218 between() calls crashes ffmpeg during filter graph initialization — OOM, no output.

Fix: write cut points to a segment list file and use the ffmpeg segment muxer, or run it in Python batches of 20 segments at a time.

5. SiliconFlow ASR returns empty word-level timestamps

Called SiliconFlow’s speech recognition API with word-level timestamp enabled. Got back a response with empty segments and words lists — only top-level text had content.

Not a code bug. Some models (especially the fast variants) only support utterance-level output, not word-level. Check the model’s capability docs or switch to a full Whisper large-v3 equivalent.

6. set -e + Remotion render causes premature script exit

Batch script starts with set -e, then:

npx remotion render MyComp output.mp4
ffmpeg -i output.mp4 ...

Remotion writes an incomplete mp4 while rendering. The next ffmpeg line reads it, gets a non-zero exit code, and set -e kills the whole script.

Fix option 1: chain with && instead of newlines. Fix option 2: wrap the render line with set +e and set -e to handle its exit code separately.

7. pgrep -lf deadlocks on itself

Waiting for a render to finish with:

while pgrep -lf "remotion render"; do sleep 10; done

This loop never exits. The shell process running the while loop has "remotion render" in its own argv, so pgrep -lf always matches itself.

Three actual fixes:

# 1. Anchor to the real process
pgrep -f '^node.*remotion'

# 2. Track the PID directly
npx remotion render & PID=$!; wait $PID

# 3. Monitor the output file size until it stabilizes

8. yt-dlp subtitle language codes are inconsistent

Tried downloading with --sub-lang zh-Hant. But YouTube’s actual language tags can be zh-Hant, zh-TW, or auto-generated ones like zh-Hant-RsSZZSfhlqk (with a random hash appended). Hardcoding the code doesn’t work.

Check first, then download:

yt-dlp --list-subs "https://www.youtube.com/watch?v=VIDEO_ID"
# Use whatever code actually shows up
yt-dlp --sub-lang zh-Hant-RsSZZSfhlqk --write-sub --no-download ...

9. YouTube Data API caption quota is only 10,000 units per day

The standard quota for the YouTube Data API is 10,000 units per day. Caption operations (captions.list, captions.download) each cost quota. Run a batch script without checking your remaining quota first and you’ll burn through it mid-run.

Quota resets at midnight PDT — which is 2pm the next day in Taiwan. Plan accordingly, or you’ll wake up to a stalled pipeline wondering why nothing is uploading.

Every automated pipeline hits bugs. The only way to save time in the long run is to write them down when they happen. This list will keep growing.