Pre-trigger buffer

[jaajee]

Hi,
I'm not sure if my finding is a bug or an issue, this is why I'm posting it here first. Here is what I'm struggling with:

Pre-trigger buffer not spliced into motion-triggered recordings

Build: prudynt-t 313414b92c (Jun 22 2026 18:03:14)
Firmware: thingino ciao+efc921c
Camera: Wyze Cam v3 (wyze_cam3_t31x_gc2053_atbm6031)

Description

PreTriggerBuffer initializes correctly at startup for both channels (5s duration, 5MB limit), but it is never consulted when a motion event triggers a recording. Motion-triggered clips start exactly at the moment motion is detected (or ~1 second later), with no pre-roll, despite recorder.prebuffer_enabled: true and recorder.prebuffer_seconds: 5 in prudynt.json.

Config

"recorder": {
    "enabled": true,
    "autostart": false,
    "prebuffer_enabled": true,
    "prebuffer_seconds": 5,
    "prebuffer_max_memory_mb": 5
}

Relevant log — startup

Jun 22 14:03:36 prudynt[649]: [INFO:PreTriggerBuffer.cpp]: PreTriggerBuffer initialized: 5s duration, 5MB limit, max_capacity=300, keyframe_only=0
Jun 22 14:03:36 prudynt[649]: [INFO:VideoWorker.cpp]: PreTriggerBuffer initialized for channel 0
Jun 22 14:03:36 prudynt[649]: [INFO:PreTriggerBuffer.cpp]: PreTriggerBuffer initialized: 5s duration, 5MB limit, max_capacity=300, keyframe_only=0
Jun 22 14:03:36 prudynt[649]: [INFO:VideoWorker.cpp]: PreTriggerBuffer initialized for channel 1

Relevant log — actual motion trigger

Aug 15 13:30:27 prudynt[649]: [INFO:Motion.cpp]: Motion Start
Aug 15 13:30:27 prudynt[649]: [INFO:MP4ControlSocket.cpp]: MP4ControlSocket: raw command buffer ('START /tmp/motion_20260815_133027.mp4 10 0 ') length=43
Aug 15 13:30:27 prudynt[649]: [INFO:MP4ControlSocket.cpp]: MP4ControlSocket: parsed op='START'
Aug 15 13:30:27 prudynt[649]: [INFO:MP4ControlSocket.cpp]: MP4ControlSocket: START requested, path='/tmp/motion_20260815_133027.mp4' duration=10s channel=0
Aug 15 13:30:27 prudynt[649]: [INFO:MP4Muxer_simple.cpp]: SimpleMP4Muxer: audio enabled sample_rate=16000Hz channels=1 config_bytes=2
Aug 15 13:30:27 prudynt[649]: [INFO:MP4ControlSocket.cpp]: MP4ControlSocket: recorder started with avcC payload size=55 on channel 0

No PreTriggerBuffer log lines appear anywhere after initialization — not during this event or any other motion trigger in the session.

Analysis

The motion daemon (via motion.script_path → motion-mountguard) triggers recording by writing a plain START <path> <duration> <channel> command to the /run/prudynt/mp4ctl FIFO, handled by MP4ControlSocket/SimpleMP4Muxer. This protocol has no parameter for pulling frames from PreTriggerBuffer, and nothing in MP4ControlSocket.cpp appears to reference the buffer when starting a new recording. The buffer fills continuously in memory but is never read from.

Expected behavior

With prebuffer_enabled: true and prebuffer_seconds: 5, a motion-triggered clip should include ~5 seconds of buffered footage prior to the Motion Start timestamp.

Actual behavior

Clips start exactly at the Motion Start timestamp with zero pre-roll, even though PreTriggerBuffer is active and has frames available.

Environment

• recorder.enabled: true, recorder.autostart: false (motion-only recording, no continuous recording)
• Motion clips delivered via NFS (motion.send2storage: true)
• stream0: 1920x1080, H264, 3000kbps, 30fps