ExactCut Video Tools: A Lossless, VFR-Aware Cutlist Pipeline

ExactCut is a suite of Python and Batch scripts designed to bridge the gap between visually editing video via proxy files and performing frame-accurate, lossless cuts using FFmpeg.

This workflow guarantees that no frames are lost, prevents desync issues common with Variable Frame Rate (VFR) footage, and automatically snaps your edits to safe I-frame boundaries.

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📂 Directory Setup

Before you begin, your working folder must be prepared correctly. The scripts look for specific files in the same directory to function.

Your folder must contain:

1. Source Video(s): The original files.
2. The Entire Scripts Folder: The contents of \ExactCut-Video-Tools\scripts must be copied here.

• Crucial: For "Open GOP" codecs (like x265), you must set "i_frame_offset" to "2" in vdscript_range_adjuster.py.

3. Correctly Named .vdscript Files: Once you finish editing, your VirtualDub2 scripts must follow this strict format: [Source_Video_Name].[Original_Extension].vdscript

Example: > If your source is Vacation.mp4, your script must be named Vacation.mp4.vdscript.

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🛠️ The Workflow Pipeline

Phase 1: Preparation & Editing

⚠️ PRO-TIP: Organize by Framerate! > We highly recommend placing videos with different framerates into separate folders. The ExactCut FFmpeg Cutter uses a default "Seek Nudge" of 133ms.

• At 30 fps: 133ms is ~4 frames (Minimum GOP needed: 5).
• At 60 fps: 133ms is ~8 frames (Minimum GOP needed: 9).

1. Extract Frame Logs (1_Verify_and_Log.bat): Extracts precise _frame_log.txt files for every video. This is your "ground truth" for VFR timestamps.
2. Generate Proxy Videos (for HD/4K etc): Import the provided .json presets.

• High Power (720p): For modern desktops.
• Low Power (400p): Optimized for older/budget PCs using the ultrafast baseline profile.

3. Edit in VirtualDub2: Load your proxy (or the original if you skipped proxy creation), and make your cuts.

• **NOTE: VirtualDub2 is endpoint exclusive — meaning that the frame you end the selection on is NOT included in the selection!
• Save Your Cutlist: Once your editing is complete, go to File > Save processing settings... (CTRL + S).
• Crucial: MAKE SURE to check "Include selection and edit list" in the save dialog. Otherwise, your cuts will NOT be saved! VirtualDub2 will remember this setting for future sessions.
• Naming Convention: The vdscript must be saved with the format source_video_filename.extension.vdscript. So, if your source video is called whatever.mp4, your final saved vdscript should be called whatever.mp4.vdscript.

Phase 2: Analysis & Conversion

Run 2_Analyze_and_Prepare.bat. This automated script handles:

• Adjustment: Snaps cut points to legal I-frames.
• VFR Info: Generates a human-readable _info.txt summary.
• GOP Analysis: Checks if the starting GOP of each cut is long enough for the FFmpeg "Seek Nudge."
• VFR Detector: Scans for severe timing anomalies in the source.
• Cutlist Generation: Produces the final timecode list for the Cutter.

Phase 3: Cut the Video into Individual Segments

Open exactcut_ffmpeg_cutter.pyw, load your source folder, and click Start Cutting. All the parts will be saved to subfolders (same names as source videos).

Phase 4: Merge

Open LosslessCut, go to Tools > Merge/concatenate files, browse for desired folder, select all the parts, then merge. Repeat this process until all the parts in each subfolder have been merged - & that's it - FINITO!

• Cleanup: Use the 🧹 Cleanup button inside the ExactCut FFmpeg Cutter to automatically sweep all the temporary scripts, cutlists, and log files into a delete folder to keep your workspace tidy.

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✅ User Best Practices

To ensure maximum file stability and compatibility with all media players after cutting:

• The 5-Second Rule: Aim for a minimum of 5 seconds between each segment. Cuts placed too close together can occasionally cause playback "hiccups" in certain hardware decoders.
• Verification: Always keep your _frame_log.txt files until you have verified the final output. They are the only way to pinpoint the exact keyframe positions used by the scripts.

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🔍 Troubleshooting & Safety

"Smallest starting GOP" is too small?

If gop_analyzer.py reports a GOP size smaller than your framerate's requirement, use the Editor feature in ExactCut FFmpeg Cutter GUI to fix it:

Scenario 1: Use "1. Expand Start Earlier"

If there is plenty of room between segments, push the Start Time of the offending segment back by 1 second.

1. Reference your _frame_log.txt to find a safe I-frame at least 1 second earlier.
2. Choose the line #, enter "1" in the "Seconds" field and click Apply Expansion.

Scenario 2: Use "2. Bridge Gap"

If pushing the start time back violates the 5-second rule or causes an overlap:

1. Select the offending segment and the one preceding it.
2. Click Apply Bridge. This merges them into one continuous cut, bypassing the GOP issue entirely.

Missing Frame Logs or Scripts Skipping Files?

• Check Names: Ensure your .vdscript includes the original extension (e.g., .mp4.vdscript).
• Missing Logs: Run 1_Verify_and_Log.bat again to ensure the _frame_log.txt was created.

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⚙️ Requirements

• Python 3.x
• **LosslessCut
• FFmpeg (Standalone or via LosslessCut)
• VirtualDub2 (build 44282 or similar)
• HandBrake (For proxy generation)

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