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Caption Synchronization

Keep captions perfectly synchronized with your video.

Sync Basics​

Perfect synchronization means:

  • Captions appear when speech begins
  • Captions disappear when speech ends
  • Reading pace matches speaking pace
  • No drift over time

Sync Methods​

1. Visual Sync (Waveform)​

Use audio waveform to see speech:

  1. View waveform timeline
  2. Identify speech patterns
  3. Align caption edges with waveform peaks
  4. Verify with playback

2. Audio Sync (Listening)​

Listen and adjust:

  1. Play video
  2. Listen for speech start
  3. Pause and adjust caption start
  4. Repeat for end time

3. Reading Sync​

Ensure captions are readable:

  1. Play with captions
  2. Read along
  3. Adjust if too fast/slow
  4. Verify comfortable reading pace

Drift Correction​

What is Drift?​

Captions gradually go out of sync over time.

Causes:

  • Frame rate mismatch
  • Encoding issues
  • Manual timing errors

Detecting Drift​

Signs of drift:

  • First captions sync well
  • Later captions increasingly off
  • Consistent delay pattern

Fixing Drift​

Method 1: Re-sync Points

  1. Find known sync point (beginning)
  2. Find where drift is noticeable
  3. Calculate offset
  4. Apply correction from that point

Method 2: Time Scaling

  1. Measure drift amount
  2. Calculate scale factor
  3. Scale all caption times
  4. Verify sync at multiple points

Method 3: Manual Adjustment

  1. Find major sync points throughout video
  2. Adjust nearby captions to match
  3. Interpolate between sync points

Multi-Speaker Sync​

For content with multiple speakers:

Speaker Transitions​

  • End previous speaker's caption when they stop
  • Start next speaker's caption when they begin
  • Use minimal gap (0.25-0.5s)

Overlapping Speech​

Options:

  1. Show both captions simultaneously (top/bottom)
  2. Alternate rapidly
  3. Combine into single caption

Speaker Identification​

Include speaker names:

[John]: Welcome everyone
[Mary]: Thanks for joining us

Auto-Sync Features​

Speech Detection​

Automatically detect speech boundaries:

  1. Enable speech detection
  2. System analyzes audio
  3. Captions auto-aligned to speech
  4. Manual review recommended

Beat Sync​

Sync to music beats:

  1. Detect beats in audio
  2. Align captions to beat grid
  3. Useful for music videos

Quality Checking​

Sync Test Checklist​

  • Play entire video
  • Check first caption syncs
  • Check mid-point syncs
  • Check final caption syncs
  • No drift detected
  • Comfortable reading pace
  • All captions within time limits

Problem Areas​

Pay extra attention to:

  • Fast speech sections
  • Multiple speakers
  • Background music
  • Sound effects
  • Long videos (>30 min)

Next Steps​