5.4 USB camera no image

Typical symptoms

After launching hobot_usb_cam (or similar) the node shows running, but:

• Web preview stays black
• Logs repeat did not receive image data
• The node exits with code -6, SIGABRT, or terminate called after throwing …

Quick check

On the board:

v4l2-ctl -d /dev/video0 --list-formats-ext

Look for [0]: 'MJPG' (Motion-JPEG) in the output:

• No MJPG → camera may be YUYV-only; try low resolutions such as 320x240
• Has MJPG → set launch pixel_format=MJPEG, pick resolution/fps the camera lists as supported

Checklist

1. Identify the /dev/video node

   ls -l /dev/video*

   Multiple devices:

   for d in /dev/video*; do
     echo "=== $d ==="
     v4l2-ctl -d $d --list-formats-ext 2>/dev/null | head -20
   done

2. Switch pixel format

   UVC often defaults to YUYV—on tight USB bandwidth the stream stalls. Prefer MJPEG—e.g. in launch:

   pixel_format='MJPEG'
   image_width=640
   image_height=480
   framerate=30

3. Match reported modes

Width, height, and fps should match a line from v4l2-ctl. Drop to 320x240@15 if needed.

4. Try another device node

   If /dev/video0 crashes, try /dev/video1, etc.

5. Paste logs

   Drop the full traceback into AI Dock—Moss can suggest RDK‑specific fixes.

Why this works

Defaults that force YUYV move large payloads; extras on the same USB bus worsen drops. MJPEG squeezes bandwidth and is usually stabler.

Permanent fix workflow

Proceed stepwise:

1. Characterize modes via v4l2-ctl (formats, sizes, fps)
2. Edit launch with pixel_format='MJPEG' matching a supported combo
3. Verify topics—RViz2 or ros2 topic echo should show steady frames
4. Then stack detection/other nodes

For ROS / TROS details see official RDK documentation.