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charset=\"utf-8\"", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "From": "Javier Tia <floss@jetm.me>", "To": "libcamera-devel@lists.libcamera.org", "Date": "Wed, 04 Mar 2026 17:00:56 -0600", "Subject": "[PATCH v2 0/4] Simple pipeline: proportional AGC, AWB stats fix,\n\tOV2740 tuning", "In-Reply-To": "20260225221859.600869-1-floss@jetm.me", "References": "20260225221859.600869-1-floss@jetm.me", "Message-Id": "<20260304232519.335E61EA006B@mailuser.phl.internal>", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "Errors-To": "libcamera-devel-bounces@lists.libcamera.org", "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>" }, "content": "This series fixes AGC oscillation and an AWB statistics bug in the\nSimple pipeline, and adds the first sensor-specific tuning file for\nthe SoftISP.\n\nPatch 1 replaces the fixed 10% bang-bang step in the AGC with a\nproportional controller where step size scales with the MSV error.\nThis eliminates the brightness flicker observed on sensors with\nnon-trivial control latency (tested on OV2740 behind Intel\nIPU6/IVSC). Unchanged from v1.\n\nPatch 2 fixes a bit-depth mismatch in the statistics gathering.\nThe SWSTATS_ACCUMULATE_LINE_STATS() macro divides the luminance value\nfor the histogram to normalize it to 8-bit range, but does not apply\nthe same normalization to the RGB sums. For 10-bit and 12-bit\nunpacked Bayer formats, the sums are accumulated at native bit depth\nwhile the AWB subtracts an 8-bit black level, under-correcting by 4x\nor 16x respectively. This skews the AWB grey world gains, producing a\nvisible color cast (~9% green on the OV2740 with BLC=16). The fix\nright-shifts the RGB sums in finishFrame() to normalize them to 8-bit\nscale, matching the histogram and the 8-bit BLC used by AWB.\n\nPatch 3 adds an OV2740 tuning file. With the AWB fix from patch 2,\nno CCM is needed - AWB grey world convergence gives R/G ~ 0.98 and\nB/G ~ 0.99 under 6500K lighting.\n\nPatch 4 adds the OV2740 black level (4096, i.e. 0x40 at 10-bit) to\nCameraSensorHelperOv2740, following the established pattern used by\nOV5675, IMX219, and other sensors. This is the canonical location for\nsensor calibration data and is used across all pipeline handlers.\n\nChanges since v1:\n- Patch 2: New. Fixes the AWB/BLC bit-depth mismatch for >8-bit\n sensors, eliminating the green cast without needing a CCM.\n- Patch 3 (was patch 2 in v1): Removed CCM - no longer needed with\n the AWB fix. Removed explicit blackLevel from the tuning file;\n the value is now provided by CameraSensorHelperOv2740 (patch 4)\n as suggested by Robert Mader.\n- Patch 4 (was patch 3 in v1): Unchanged.\n\nTested on ThinkPad X1 Carbon Gen 10 (Alder Lake, OV2740, IPU6 ISYS,\nCachyOS kernel 6.19.3, libcamera 0.7.0).\n\nTest results (converged frames, 6500K lighting, no CCM):\n\n With AWB fix (v2): R/G=0.984 B/G=0.985 (~1.5% residual)\n Without fix (v1): R/G=0.910 B/G=0.904 (~9% green cast)\n BLC=0 control: R/G=1.000 B/G=1.001 (proves the mismatch)\n\nJavier Tia (4):\n ipa: simple: agc: Replace bang-bang controller with proportional\n libcamera: software_isp: Normalize statistics sums to 8-bit\n ipa: simple: data: Add OV2740 tuning file\n ipa: libipa: camera_sensor_helper: Add OV2740 black level\n\n .../internal/software_isp/swstats_cpu.h | 1 +\n src/ipa/libipa/camera_sensor_helper.cpp | 2 +\n src/ipa/simple/algorithms/agc.cpp | 73 +++++++++++++------\n src/ipa/simple/data/meson.build | 1 +\n src/ipa/simple/data/ov2740.yaml | 13 ++++\n src/libcamera/software_isp/swstats_cpu.cpp | 9 +++\n 6 files changed, 75 insertions(+), 24 deletions(-)\n create mode 100644 src/ipa/simple/data/ov2740.yaml" }