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Defraser Tutorial: Extracting Corrupt Video Files — Step-by-Step

Overview

Defraser is a forensic tool for recovering and analyzing video/audio streams from damaged or partial files and disk images. This tutorial shows a practical, step-by-step workflow to locate, extract, and validate corrupted video files using Defraser.

Prerequisites

• Defraser installed (Windows).
• Source media: disk image, device image, or corrupted video file(s).
• Sufficient disk space for recovered files.
• Basic familiarity with forensic images and file systems.

Step 1 — Create a working copy

1. Copy evidence to a secure working directory; never modify original evidence.
2. Mount or open the image in read-only mode if possible.

Step 2 — Start Defraser and create a new project

1. Launch Defraser.
2. File → New project.
3. Add your source (disk image or file) via File → Add input.

Step 3 — Configure scanning parameters

1. Choose scan types (e.g., MPEG-4, H.264, AVI, QuickTime) — select formats relevant to the case.
2. Set search depth and heuristics; use defaults unless you need deeper carving.
3. Optionally set file size limits and signature settings.

Step 4 — Run the scan (carving)

1. Start the scan. Defraser will locate stream headers, frames, and containers.
2. Monitor progress; note any warnings about fragmented or incomplete streams.

Step 5 — Review candidate streams

1. Open the Results pane.
2. For each candidate:
   • Preview the stream using the built-in player.
   • Check metadata (codec, resolution, timestamps).
   • Mark candidates as accepted, rejected, or unknown.

Step 6 — Handle fragmented or partially recovered files

1. If fragments are present, use Defraser’s reassembly features to stitch segments.
2. Manually inspect byte offsets and sequence numbers if automatic reassembly fails.
3. Try alternate codec settings if playback fails (e.g., force H.264 parsing).

Step 7 — Extract and save recovered files

1. Select accepted streams.
2. Export them to a designated output folder, choosing container format as needed.
3. Keep exported originals and a working copy for analysis.

Step 8 — Validate extracted files

1. Play exported files in multiple players (VLC, FFmpeg) to verify integrity.
2. Use FFmpeg to probe file details:

bash
Copy CodeCopied
ffprobe -v error -show_format -show_streams recoveredfile.mp4 

bash
 ffON2NH02oMAcqyoh2UU MQCbz04ET5EljRmK3YpQ CPXAhl7VTkj2dHDyAYAf” data-copycode=“true” role=“button” aria-label=“Copy Code”>Copy CodeCopied
sha256sum recoveredfile.mp4 

bash
 ffON2NH02oMAcqyoh2UU MQCbz04ET5EljRmK3YpQ CPXAhl7VTkj2dHDyAYAf” data-copycode=“true” role=“button” aria-label=“Copy Code”>Copy CodeCopied
ffmpeg -f h264 -i input.h264 -c copy out.mp4