Recording

• What and When
• Files on Disk
• Rotation
• On-demand Recording
• Browsing Recordings
• Storage Setup
• Making a Timelapse

What and When複製段落連結

Recording is controlled by two independent options. --record-type decides what is captured and --record-mode decides when:

Nothing is recorded until a path is set. The background recorder needs --record-path, and the on-demand recorder needs --record-ondemand-path — which defaults to <record-path>/on-demand/ when you leave it out. Both must be absolute paths, and the recorder stays off if the directory cannot be created.

/path/to/pi-webrtc ... --record-path=/mnt/ext_disk/video

Files on Disk複製段落連結

Files are bucketed by date and hour, and named for the moment they start:

/mnt/ext_disk/video/
└── 20260730/
    ├── 09/
    │   ├── 20260730_090000.mp4
    │   ├── 20260730_090000.jpg
    │   ├── 20260730_090100.mp4
    │   └── 20260730_090100.jpg
    └── 10/
        └── ...

Every MP4 gets a matching .jpg preview taken from the video, which is what makes the thumbnail grid in a client cheap to draw. --file-duration sets how long each file runs — 60 seconds by default — and doubles as the interval between snapshots in snapshot mode. --jpeg-quality applies to snapshots and thumbnails alike.

Rotation複製段落連結

A background thread wakes every 60 seconds and checks the free space on the recording volume. While less than 400 MB is free it deletes the oldest hour's files, one at a time, until it is back above the threshold. MP4 and .jpg files are removed as a pair, and date and hour directories are cleaned up once they empty out.

This means the recording volume settles at "as much history as fits" rather than filling up and stopping. Give it a dedicated disk or image file if you don't want it competing with the rest of the system — see Storage Setup.

On-demand Recording複製段落連結

With --record-mode=on-demand (or both), a connected client starts and stops recording over the DataChannel rather than the device recording continuously. Useful when you want footage of events, not of everything.

The response carries the path of the file being written, so the client can request it afterwards with TRANSFER_FILE.

These recordings land under --record-ondemand-path, kept separate from the background recordings so that rotation and browsing treat them independently.

Browsing Recordings複製段落連結

Clients list and fetch recordings over the same DataChannel. QUERY_FILE returns metadata — path, duration, and a downscaled base64 JPEG thumbnail — and TRANSFER_FILE streams the file itself in chunks.

QueryFileRequest takes a type and a parameter:

The mode field selects which set of files to search:

• RECORDING — the recordings under --record-path, in the date/hour layout above.
• TIMELAPSE — a flat <record-path>/timelapse directory, for timelapse videos you have assembled yourself.

Also available on the DataChannel: TAKE_SNAPSHOT for a one-off JPEG at a requested quality, and CONTROL_CAMERA for runtime image controls.

Storage Setup複製段落連結

Using a USB drive複製段落連結

1. Find the drive:

   複製

   sudo fdisk -l

2. Mount it at /mnt/ext_disk with autofs (reference):

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   sudo apt-get install autofs
   echo '/- /etc/auto.usb --timeout=5' | sudo tee -a /etc/auto.master > /dev/null
   echo '/mnt/ext_disk -fstype=auto,nofail,nodev,nosuid,noatime,async,umask=000 :/dev/sda1' | sudo tee -a /etc/auto.usb > /dev/null
   sudo systemctl restart autofs

3. Point --record-path at it:

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   /path/to/pi-webrtc ... --record-path=/mnt/ext_disk/video

Using a virtual disk file複製段落連結

No USB drive needed — cap recording at a fixed size by giving it a disk image.

1. Create a 16 GB image:

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   dd if=/dev/zero of=/home/pi/16gb.img bs=1M count=16384

2. Format it:

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   mkfs.ext4 /home/pi/16gb.img

3. Mount it:

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   mkdir -p /home/pi/limited_folder
   sudo mount -o loop /home/pi/16gb.img /home/pi/limited_folder

4. Make it writable:

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   sudo chmod 777 /home/pi/limited_folder

5. Record into it:

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   /path/to/pi-webrtc ... --record-path=/home/pi/limited_folder/

6. Optionally mount it at boot by adding this to /etc/fstab:

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   /home/pi/16gb.img  /home/pi/limited_folder  ext4  loop,noatime  0  2

Making a Timelapse複製段落連結

Turn the .jpg files from snapshot mode into a 30 fps MP4.

1. Build the file list. ffmpeg -f concat wants one file '...' per line, in order:

find /mnt/ext_disk/video/20260509/ -type f -iname "*.jpg" | sort | sed "s/^/file '/; s/$/'/" > file_list.txt

2. Encode it:

ffmpeg -f concat -safe 0 -i file_list.txt -r 30 -c:v libx264 -pix_fmt yuv420p timelapse.mp4

• -safe 0 allows absolute paths in the list.
• -r 30 sets the output frame rate.
• -pix_fmt yuv420p keeps it playable in browsers and on phones.

Put the result in <record-path>/timelapse/ and clients can browse it through QUERY_FILE with mode: TIMELAPSE.