Video Recording

Recording a Subtitled Video Session

Record the Podman Desktop Xvfb display while navigating the app, then produce an MP4 with burned-in subtitles describing each section visited.

Prerequisites

• Podman Desktop must already be running on Xvfb display :99 with CDP on port 9222. Use the interactive-podman-desktop skill to set that up.
• A Playwright MCP server connected to the CDP endpoint, so you can navigate the app via mcp__playwright__browser_* tools.

Step 0 — Install prerequisites

The xdpyinfo tool is required to detect the Xvfb display resolution:

sudo dnf install -y xdpyinfo

Step 1 — Install ffmpeg

bash .agents/skills/video-recording/scripts/install-ffmpeg.sh

Step 2 — Maximize the Electron window

The Electron window may not fill the Xvfb display by default, leaving black borders in the recording. Maximize it before recording:

bash .agents/skills/video-recording/scripts/maximize-window.sh

Verify the window fills the display:

DISPLAY=:99 ffmpeg -y -f x11grab -video_size 1024x768 -framerate 15 \
  -i :99 -frames:v 1 -update 1 /tmp/check-frame.png 2>/dev/null

Then read /tmp/check-frame.png to confirm no black borders.

Step 3 — Record the session

Start recording

bash .agents/skills/video-recording/scripts/start-recording.sh [output-path]

• Default output: ./recording-raw.mp4
• Saves PID to /tmp/video-recording.pid
• Saves start timestamp (epoch ms) to /tmp/video-start-time
• Uses libopenh264 encoder (available in ffmpeg-free on Fedora)

Navigate and collect timestamps

While recording, navigate the app using Playwright MCP tools. Before and after each navigation action, capture a timestamp:

date +%s%3N

Keep a log of (timestamp_ms, subtitle_text) pairs as you navigate. For example:

Stop recording

bash .agents/skills/video-recording/scripts/stop-recording.sh

Step 4 — Build the SRT subtitle file

Use the collected timestamps and the start time to create an SRT file. The helper script converts absolute epoch-ms timestamps to SRT timecodes:

bash .agents/skills/video-recording/scripts/build-srt.sh <output.srt> \
  <start_ms> \
  <begin_ms>,<end_ms>,<"subtitle text"> \
  <begin_ms>,<end_ms>,<"subtitle text"> \
  ...

Example:

bash .agents/skills/video-recording/scripts/build-srt.sh \
  ./demo.srt \
  1786540681068 \
  1786540681068,1786540693000,"Kubernetes Dashboard - Connected to cluster" \
  1786540693583,1786540701000,"Nodes - Cluster node information" \
  1786540702439,1786540712000,"Deployments - Application workloads" \
  1786540713931,1786540717000,"Dashboard - Cluster metrics overview"

Step 5 — Burn subtitles into the final video

bash .agents/skills/video-recording/scripts/burn-subtitles.sh \
  <raw-video> <srt-file> <output-video> [max-duration-seconds]

Example:

bash .agents/skills/video-recording/scripts/burn-subtitles.sh \
  ./recording-raw.mp4 ./demo.srt ./demo-subtitled.mp4 37

The optional duration argument trims the video. Subtitles are rendered with a white font, black outline, and bottom margin.

Step 6 (optional) — Speed up the video

To create a sped-up version (e.g. 4x), use the speedup-video.sh script after burning subtitles:

bash .agents/skills/video-recording/scripts/speedup-video.sh \
  <subtitled-video> <output-video> <speed-factor>

Example:

bash .agents/skills/video-recording/scripts/speedup-video.sh \
  ./demo-subtitled.mp4 ./demo-4x.mp4 4

Important: Always burn subtitles first at 1x speed, then speed up the subtitled video. This way the SRT timecodes don't need adjustment. Speeding up first and then trying to burn subtitles requires manually dividing all SRT timecodes by the speed factor.

Quick Reference

Full workflow in one block:

# 1. Install & maximize
bash .agents/skills/video-recording/scripts/install-ffmpeg.sh
bash .agents/skills/video-recording/scripts/maximize-window.sh

# 2. Record
bash .agents/skills/video-recording/scripts/start-recording.sh ./raw.mp4

# 3. (navigate the app, collect timestamps)

# 4. Stop & produce final video
bash .agents/skills/video-recording/scripts/stop-recording.sh
bash .agents/skills/video-recording/scripts/build-srt.sh ./demo.srt <start> <entries...>
bash .agents/skills/video-recording/scripts/burn-subtitles.sh ./raw.mp4 ./demo.srt ./demo-subtitled.mp4
bash .agents/skills/video-recording/scripts/speedup-video.sh ./demo-subtitled.mp4 ./demo-4x.mp4 4

Notes

• ffmpeg-free on Fedora does not include libx264. Use libopenh264 instead.
• The Xvfb display defaults to :99. If a different display is used, set DISPLAY before running the scripts.
• The default Xvfb resolution in start-xvfb.sh is 1024x768, matching the default recording size. Override with XVFB_RESOLUTION=1920x1080 and VIDEO_SIZE=1920x1080 for full HD.
• For complex interactions (Monaco editor, multi-tab dialogs), experiment without recording first to work out the exact steps. Once the flow is reliable, start a fresh recording. This avoids long retake sequences that need to be trimmed out.
• When editing in Monaco during a recording, use the Enter → Shift+Home → Delete sequence to bypass auto-indent before typing each new line. See the interactive-podman-desktop skill's Monaco Editor section for details.