indi_libcamera_ccd Known Issues - aaronwmorris/indi-allsky GitHub Wiki

indi_libcamera_ccd Known Issues & Driver Tuning

The indi_libcamera_ccd driver is an INDI-native C++ driver interface for MIPI-CSI sensors managed by the Raspberry Pi libcamera subsystem (e.g., Raspberry Pi Camera Module 3, HQ Camera, Global Shutter Camera). While offering low latency and direct hardware integration, several driver-level anomalies require specific configuration adjustments.

1. Documented Driver Characteristics

  • Zero Gain Fault: The driver permits setting gain to 0, which can cause internal pipeline hangs or severe frame timeout errors. Minimum operational analog gain must be set to 1.0.
  • Analog vs. Digital Gain Ceiling:
    • Sony IMX477 (Raspberry Pi HQ Camera): Maximum analog gain is 22.62.
    • Sony IMX708 (Camera Module 3) and IMX296 (Global Shutter): Maximum analog gain is 16.0.
    • Setting gain values exceeding these ceilings engages digital gain, which amplifies sensor read noise and quantization error.
  • Minimum Exposure Reporting: The driver may report 0.0 seconds as the minimum exposure value, causing auto-exposure division errors. Set the manual minimum daytime exposure limit to 0.000032 seconds.
  • Offset / Black Level Calibration: In native 12-bit DNG/RAW streaming, libcamera imposes a fixed black level pedestal (often 4096 on 16-bit stretched buffers) that must be accounted for during bias/dark frame calibration.
  • Auto White Balance (AWB): Dynamic AWB changes color balance frame-to-frame, interfering with daytime timelapse consistency and star detection. AWB should be disabled in favor of static color gain multipliers.

2. Recommended Configuration Preset

Under Camera Settings -> INDI Custom Properties / Switches, apply the following overrides:

{
    "PROPERTIES": {
        "Adjustments": {
            "AwbRed": 1.0,
            "AwbBlue": 1.0
        }
    },
    "SWITCHES": {
        "CCD_CAPTURE_FORMAT": {
            "on": [
                "DNG"
            ],
            "off": [
                "JPG"
            ]
        }
    }
}

Exposure and Gain Limits

  • Daytime Min Gain: 1.0
  • Daytime Max Gain: 1.0
  • Daytime Min Exposure: 0.000032
  • Nighttime Max Gain: 16.0 (or 22.62 for IMX477)

3. Upstream References