Replace Microsoft 365 with Free Tools for Offline Video Captioning and Metadata Editing

Cut the Microsoft 365 cord: free offline tools for captioning, batch subtitle conversion, and metadata

Pain point: you download dozens of videos, need accurate transcripts, consistent subtitles in multiple formats, and correct metadata — but you don’t want to pay for Microsoft 365 or rely on cloud services that expose private data. This guide shows how to replace Microsoft 365 with LibreOffice plus a set of free offline tools to edit transcripts, run batch subtitle conversions, and manage metadata safely and efficiently in 2026.

The short answer (what you’ll learn)

• How to use LibreOffice Writer and Calc for transcript cleanup and to prepare SRT/VTT files.
• Which free command-line tools (ffmpeg, mkvtoolnix, exiftool, mediainfo) you’ll need for batch conversion and embedding.
• Practical scripts and step-by-step workflows for batch subtitle conversion and metadata editing — ready for automation.
• Privacy, legal, and 2026 trends that change how you should architect offline captioning workflows.

Why ditch Microsoft 365 for offline captioning in 2026?

By 2026, two forces make offline, free tools compelling for creators and publishers: (1) local speech models and transcription tooling matured in late 2024–2025, making high-quality offline transcripts feasible; and (2) open-source utilities gained ongoing maintenance and performance improvements. If your goals are privacy, batch scale, and tight integration with content pipelines, using LibreOffice plus robust CLI tools is often faster and cheaper than cloud-first office suites.

“Offline-first workflows let you keep everything on-premises, avoid recurring SaaS fees, and automate batch processing.”

Toolset you’ll install (all free, offline)

• LibreOffice (Writer, Calc) — core transcript editing and CSV-to-SRT workflows
• ffmpeg — subtitle format conversion, embedding, audio extraction
• mkvtoolnix (mkvmerge, mkvpropedit) — mkv subtitle and metadata work
• exiftool — MP4/MOV/MP3 metadata batch editing
• MediaInfo — inspect container and codec metadata
• Python 3 and lightweight libraries (optional) — for robust CSV-to-SRT conversion and automation (use the built-in stdlib to avoid extra deps)
• Local ASR options (optional): faster-whisper, WhisperX, VOSK, Silero — for offline transcription (matured in 2024–2025)

Overview: three core workflows

1. Transcript cleanup in LibreOffice Writer (human QC + style)
2. Batch subtitle generation & conversion (Calc + Python + ffmpeg)
3. Metadata inspection and bulk editing (MediaInfo + exiftool/mkvpropedit)

1) Clean transcripts with LibreOffice Writer — the practical method

LibreOffice Writer is your offline replacement for Word when you need to edit transcripts, track changes, and apply consistent style (speaker labels, timestamps). It’s low-friction and works fully offline.

Quick steps:

1. Open raw transcript (from local ASR) in Writer. Most ASR outputs are plain text or VTT/SRT — import directly.
2. Use Find & Replace to normalize speaker labels, remove filler words, and fix line breaks. Example: Replace double line breaks with paragraph breaks for consistent segmentation.
3. Use Writer’s Styles (Heading, Subtitle) to tag speaker cues. Export a cleaned plain-text or CSV export when you’re done.
4. For review workflows, enable Track Changes and export to ODT or DOCX for collaborators who still use Microsoft 365 — but keep edits local when possible.

Pro tip: Keep timestamps in a separate column

When preparing subtitles, keep the transcript text and timestamps as two fields. It makes later conversion to SRT/VTT deterministic, and LibreOffice Calc is excellent at tabular timestamp manipulation.

2) Batch subtitle conversion: LibreOffice Calc → SRT/VTT → embed

This is the core replacement for Microsoft Excel-based subtitle workflows. Use Calc to align timestamps and text, then export to CSV and convert to SRT with a tiny script — or use ffmpeg for direct format conversion.

Step-by-step: create SRT from a transcript table

1. In LibreOffice Calc, create columns: Index, Start (seconds or HH:MM:SS.ms), End (seconds or HH:MM:SS.ms), Text.
2. Use formulas to format times as SRT timestamps. A simple approach: keep Start/End as seconds with milliseconds (e.g., 12.345), then use Python to format when converting to SRT — avoids locale issues in Calc.
3. Export the sheet as CSV (UTF-8) with a safe delimiter (pipe | or TAB).
4. Run a small Python script to read the CSV and write a compliant .srt file.

Sample Python script (save as csv2srt.py):

#!/usr/bin/env python3
import csv
from math import floor

def fmt_ts(sec):
    # sec is float seconds
    h = int(sec // 3600)
    m = int((sec % 3600) // 60)
    s = int(sec % 60)
    ms = int(round((sec - floor(sec)) * 1000))
    return f"{h:02d}:{m:02d}:{s:02d},{ms:03d}"

with open('subs.csv', newline='', encoding='utf-8') as f_in, open('output.srt', 'w', encoding='utf-8') as f_out:
    reader = csv.DictReader(f_in)
    for row in reader:
        idx = row.get('Index') or row.get('index') or ''
        start = float(row['Start'])
        end = float(row['End'])
        text = row['Text'].replace('\\n', '\n')
        f_out.write(f"{idx}\n{fmt_ts(start)} --> {fmt_ts(end)}\n{text}\n\n")

This approach avoids locale-dependent formatting inside Calc and gives you precise control.

Convert SRT to VTT or other formats with ffmpeg

ffmpeg is the swiss-army knife for subtitle format conversion and embedding. Examples:

ffmpeg -i input.srt output.vtt

# Embed SRT as mov_text inside MP4 (for iOS/YouTube compatibility)
ffmpeg -i video.mp4 -i subs.srt -c copy -c:s mov_text output-with-subs.mp4

# Remux into MKV keeping subtitle track (better for multiple subtitle formats)
ffmpeg -i video.mp4 -i subs.srt -c copy output.mkv

Batch conversion script

Use a bash script to convert all CSVs to SRT (calls the Python converter), then convert to VTT and embed or remux.

#!/bin/bash
for csv in *.csv; do
  base=$(basename "$csv" .csv)
  python3 csv2srt.py <(sed -n '1p' "$csv") # or call script that reads specific file
  ffmpeg -i "$base.srt" "$base.vtt"
  # Embed into corresponding MP4 if exists
  if [ -f "$base.mp4" ]; then
    ffmpeg -i "$base.mp4" -i "$base.srt" -c copy -c:s mov_text "${base}-subbed.mp4"
  fi
done

3) Metadata editing and quality checks (fast, offline)

Good metadata makes your downloaded videos searchable and consistent in CMS systems. Use MediaInfo to inspect, and exiftool (MP4/MOV) or mkvpropedit (Matroska) to write metadata in bulk.

Read metadata with MediaInfo

mediainfo --Output=JSON video.mp4 > video-metadata.json

Batch edit MP4 metadata with exiftool

Common tags: Title, Artist (Creator), Comment (Description), DateTimeOriginal (publication date), Copyright.

# Set title for all MP4s in a folder
exiftool -overwrite_original -Title="My Show - Episode 1" *.mp4

# Set multiple fields from a CSV (Title, Description)
exiftool -csv=metadata.csv -overwrite_original

Your metadata.csv should include a SourceFile column with filenames. LibreOffice Calc can be used to build that CSV and then saved as UTF-8 — an easy replacement for Excel.

Edit MKV tags (use mkvpropedit and mkvmerge)

# Add a tag file (XML) to an MKV
mkvpropedit video.mkv --tags all:tags.xml

Generate tags.xml programmatically when you have many files — use LibreOffice to prepare per-file data and export as a simple CSV, then a small script to emit MKV tag XML for mkvpropedit.

Automation & integration (scale without paying SaaS)

Once you have a working pipeline locally, you can automate it with cronjobs (Linux/macOS) or Task Scheduler (Windows). Typical automation steps:

• Download videos into a monitored folder (use your trusted downloader tool).
• Run offline ASR (WhisperX/faster-whisper) to generate raw transcripts.
• Run a cleanup script that launches LibreOffice in headless mode to export needed fields or converts ODT to plain text for automated processing.
• Run csv2srt + ffmpeg to produce and embed subtitle tracks.
• Use exiftool/mkvpropedit to add metadata and move processed files to publishing folders, then store processed assets in a reliable place (see edge storage for small SaaS notes).

Example headless LibreOffice export (useful in automation)

libreoffice --headless --convert-to csv "transcript.ods" --outdir /tmp

LibreOffice's headless mode lets you convert ODT/ODS files to CSV for scripted pipelines — a reliable Microsoft 365 alternative that runs offline. If you need a more orchestrated automation layer, consider lightweight orchestrators and workflow tools that simplify local pipelines (FlowWeave).

Quality control: what to check before you publish

• Subtitle sync: spot-check 10–20% of generated subtitles against video timestamps.
• Encoding & character sets: ensure UTF-8 — LibreOffice export and Python should be set to UTF-8 to avoid mojibake.
• Metadata consistency: run a CSV comparison between expected metadata and embedded values (exiftool -j *.mp4 to collect).
• Accessibility: ensure captions are accurate and follow style guides (speaker IDs, music cues).

Legal, copyright, and privacy notes (brief but important)

Downloading video and editing captions can raise legal questions. Always:

• Check the platform terms and copyright for the videos you download.
• Use local, offline models if content is private or sensitive to avoid cloud exposure — running models on local devices (or following guidance about refurbished devices and procurement) can reduce cloud dependencies.
• Document the rights and permission for redistribution if you plan to republish or monetize derived content.

2026 trends that change how you build offline captioning pipelines

• Better local ASR: late-2024 to 2025 improvements in faster-whisper, WhisperX, and optimized CPU decoding mean you can transcribe long videos locally with reasonable compute (no cloud cost). See notes on running local models on compact hardware (Run Local LLMs on a Raspberry Pi 5).
• Improved tooling interoperability: CLI tools (ffmpeg, exiftool, mkvtoolnix) continued active maintenance into 2025–2026, so pipelines are stable and secure.
• Privacy-first workflows: demand for on-prem processing rose in 2025, so more creators are adopting fully offline chains to control PII and creative IP. Local-first sync appliances can help move processed files without cloud exposure (Field Review: Local‑First Sync Appliances for Creators).
• Open formats and streaming platforms: more publishers accept embedded mov_text or MKV sidecars, making offline workflows easier to integrate with publishing platforms.

Real-world case study (concise)

A small podcast network moved from Microsoft 365 to LibreOffice + local ASR + the CLI toolchain in Q4 2025. The results:

• Yearly software savings: ~USD 1,200 for a 5-person team.
• Turnaround time for episode captions: dropped from 3 days to under 6 hours using automated batch scripts.
• Improved privacy for early-edit episodes (all processing remained on-prem).

Troubleshooting & tips

• If LibreOffice export changes decimal separators, export as UTF-8 and use a pipe or tab delimiter to avoid locale issues.
• If ffmpeg refuses to embed subtitles in MP4, use mov_text codec for MP4, or remux into MKV.
• When exiftool seems to not write tags, use -overwrite_original and check file permissions.
• Run mediainfo before and after processing to confirm your changes took effect.

Advanced strategies

Use LibreOffice macros for repetitive transcript cleanup

LibreOffice supports macros (Basic/Python). Create a macro that:

• Normalizes speaker labels
• Removes timestamps you don’t want
• Exports a clean CSV for your Python converter

Integrate with local APIs

For teams that want controlled automation, run a small local service (Flask or FastAPI) that watches a folder and orchestrates the steps above. Keep everything behind your firewall for privacy. If you want a more designer-first automation orchestrator, see FlowWeave 2.1 for inspiration.

Final checklist before you flip the switch

• Install LibreOffice (8.x recommended in 2025–2026) and essential CLI tools (ffmpeg, exiftool, mkvtoolnix).
• Build a sample pipeline for one video end-to-end: ASR → LibreOffice cleanup → CSV → SRT → embed → metadata tagging.
• Automate with small scripts and run tests on a batch of 10–20 videos to validate timing and metadata.
• Document the workflow and store scripts in a local Git repo for repeatability and collaboration.

Actionable takeaway

If you currently rely on Microsoft 365 to edit transcripts or manage subtitle CSVs, swap in LibreOffice for the editing step and use the command-line toolchain for all format conversion and metadata work. The combination is free, offline, auditable, and—by 2026—robust enough to handle high-volume publishing.

Start with these immediate actions:

1. Install LibreOffice + ffmpeg + exiftool + mkvtoolnix + mediainfo.
2. Run a local ASR (faster-whisper or WhisperX) for one downloaded video and import the result into Writer.
3. Export from Calc to CSV and run csv2srt.py to produce an SRT, then embed with ffmpeg.
4. Use exiftool to add consistent metadata and move the final files into your publishing pipeline.

Call to action

Ready to replace Microsoft 365 with a free, offline captioning and metadata stack? Download the starter scripts (csv2srt.py, batch embed script, sample tags.xml) from our resource page and get a reproducible pipeline up in one afternoon. If you want, tell us your current workflow and we’ll suggest a tailored automation script you can run locally.

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