Instant replay for anything with HDMI. Website: snapback.video · Contact: contact@snapback.video
Snapback turns a Raspberry Pi 5 with a USB HDMI capture card into a tiny HDMI capture box for the home network. Open it in your phone's browser and there are two buttons:
- Grab Screenshot: saves a 1920x1080 JPEG of the live HDMI input.
- Save Last 30 Seconds: saves the previous ~30 seconds (H.264 + AAC MP4).
Above them is a live view of the HDMI input: a near-real-time preview, or tap for live video with sound (a few seconds behind).
No accounts, cloud, telemetry, database, Docker, or JS build tooling. Python + FastAPI + ffmpeg + one HTML file.
Disclaimer: Snapback is a personal home project provided as-is, without warranty of any kind. The authors are not liable for lost recordings, data loss, hardware damage, or anything else arising from its use. You are responsible for what you capture, including copyright, terms of service, and recording/consent laws. It has no login, so run it only on a trusted network and never expose it to the internet. Not affiliated with Raspberry Pi, Elgato, or Apple. Read the full DISCLAIMER.md.
About $110 all in (rough US prices):
- Raspberry Pi 5, 4 GB is plenty (
$60), with an active cooler ($5) - A USB 3 HDMI capture card that does 1080p60 MJPEG, such as a generic MS2130-based one (~$20). The Elgato Cam Link 4K also works.
- A good 32 GB+ microSD card (
$10) and the official 27 W USB-C power supply ($12)
The audio device is found automatically from the capture card; set SNAPBACK_AUDIO_DEVICE to override it.
Copy-protected sources can show a solid blue screen. Cable and satellite boxes, streaming sticks, and Blu-ray players usually encrypt their HDMI output with HDCP. Your TV can decrypt it; capture cards that follow HDCP can't, so Snapback only sees blue. This is expected and can't be fixed in software. Snapback works with sources that don't use HDCP, such as computers, cameras, and game consoles (on PlayStation, turn off "Enable HDCP" in the system settings).
On Raspberry Pi OS with ffmpeg and Python 3 installed:
git clone https://github.com/dconroy/snapback.git ~/snapback
cd ~/snapback
python3 -m venv .venv
.venv/bin/pip install -r requirements.txt
.venv/bin/python -m snapback serveThen open http://<your-pi>.local:8080/ on your phone. The rolling buffer starts with the app, so give it ~30 seconds before the first replay has full length.
To add captures to Photos, install the local certificate from http://<your-pi>.local:8080/snapback-ca.crt, turn it on in the phone's certificate trust settings, then open https://<your-pi>.local:8443/. The phone can then offer Save Image or Save Video. The plain http page can only download files.
To run it as a service or start it at boot, see docs/pi-startup.md.
Environment variables, all optional. If you run Snapback as a service, put them in ~/snapback-runtime/snapback.env (KEY=value lines) and restart it.
| Variable | Default |
|---|---|
SNAPBACK_RUNTIME_DIR |
~/snapback-runtime |
SNAPBACK_MEDIA_DIR |
$SNAPBACK_RUNTIME_DIR/captures |
SNAPBACK_BUFFER_DIR |
$SNAPBACK_RUNTIME_DIR/buffer |
SNAPBACK_VIDEO_DEVICE |
/dev/video0 |
SNAPBACK_AUDIO_DEVICE |
the sound card on the same USB device as the video device, else hw:CARD=C4K,DEV=0 |
SNAPBACK_X264_PRESET |
ultrafast |
SNAPBACK_START_BUFFER |
1 (set 0 to not start the buffer, e.g. for UI work) |
GET /: the web page.GET /api/status: device detected, buffer state, buffered seconds, latest screenshot/replay, the 12 newest captures, free disk, last error.POST /api/screenshot: saves a JPEG and returns{filename, url, size_bytes, ...}.POST /api/replay: saves the last ~30 s and returns{filename, url, approx_seconds, ...}.GET /media/{filename}: serves a file from the media directory only (strict filename check, no subpaths).GET /live/frame.jpg: the buffer's newest 960x540 preview frame (refreshed ten times a second), for the live preview.GET /live/stream.m3u8: an HLS live playlist over the newest buffer segments, for live video with sound in browsers that play HLS natively, such as Safari (elsewhere the page hides the live-video toggle and keeps the frame preview). Segments are served from/live/seg_NNNNNN.ts.
Errors are JSON {"detail": "..."}: 409 if the capture device is busy, 503 if capture failed or the buffer has no footage.
uv venv --python 3.13 .venv # or: python3 -m venv .venv
uv pip install --python .venv/bin/python -r requirements-dev.txt
.venv/bin/python -m pytest -q
SNAPBACK_START_BUFFER=0 .venv/bin/python -m snapback serve --port 8080 # UI without hardwareUnit tests mock ffmpeg and need no hardware. Hardware checks are in docs/manual-verification.md.
- docs/web-app.md: how the app, rolling buffer, and device ownership work.
- docs/capture-engine.md:
CaptureEngineand CLI utilities. - docs/manual-verification.md: on-Pi verification checklist.
- docs/pi-startup.md: running as a systemd service and starting at boot.