📌 Feature Suggestion for Subtitle Edit: Drop Frame (DF/NDF) Timecode Validator and Corrector

The issue names no implementation files, tests, or entry points; begin by locating the existing Find feature and subtitle timecode handling for .scc, .sub, .stl, and frame-accurate .srt. Done would require an agreed UI location, validation and reporting behavior, optional correction for 29.97 fps DF, and tests for the stated invalid-timecode rules.

Hi!

I would like to suggest implementing a tool in Subtitle Edit that can detect and optionally correct invalid timecodes according to the Drop Frame (29.97 fps) standard. This is especially useful for subtitle formats that support frame-accurate timing (such as .sub, .scc, or .stl) using the format hh:mm:ss:ff.

🔍 Proposed Functionality:

1. Drop Frame Timecode Validation (Scan Mode):

• The tool would scan all subtitle entries and check whether any start or end timecodes are invalid according to Drop Frame rules.

• In 29.97 fps Drop Frame, certain timecodes should not exist, specifically those with:

  • frame = 00 or 01
  • second = 00
  • minute is NOT a multiple of 10

• Examples of invalid TCs in Drop Frame: 00:01:00:00, 01:02:00:01, 01:07:00:00, etc.

2. Optional Auto-Correction:

• Once detected, users could be given the option to:

  • Automatically correct the invalid timecodes by skipping to the next valid one (e.g., 00:01:00:00 → 00:01:00:02)
  • Or simply receive a report listing all the affected lines

3. UI Integration (e.g., “Find Drop Frame Errors”):

• Could be added under Tools > Drop Frame Timecode Checker

• Similar to the existing "Find" feature, it could display:

  • Line number
  • Invalid TC (start or end)
  • Suggested fix (with options to apply or skip individually or in bulk)

✅ Benefits of this Feature:

• Ensures compliance with North American NTSC broadcasting standards
• Prevents files from being rejected during quality control (QC) checks
• Saves time by eliminating the need for manual timecode adjustments

📁 Target Subtitle Formats:

• Especially relevant for formats such as:

  • .scc, .sub, .stl, .srt (when using frame-accurate TC)

• Applies to workflows using 29.97 fps Drop Frame only

This feature would be a great help for professionals working with broadcasters and post-production pipelines that rely on strict timecode compliance.

Thank you again for your continuous work on Subtitle Edit — it’s an incredible tool!