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--- doc:appunti:hardware:sjcam-8pro-ambarella-firmware-modding [2022/05/09 10:34] – [Gamma curves] niccolo
+++ doc:appunti:hardware:sjcam-8pro-ambarella-firmware-modding [2022/06/15 16:47] (current) – [White balance presets] niccolo
@@ Line 68: / Line 68: @@
 ^ U         | 0 ÷ 2048    | Multiplier for the **blue projection** (blue - luma).  |
 ^ V         | 0 ÷ 2048    | Multiplier for the **red projection** (red - luma).  |
-^ Y-offset  | -128 ÷ 127  | Shift brightness from **black** to **white**. |
+^ Y-offset  | -128 ÷ 127  | Shift brightness from **black** to **white**.  |
-^ U-offset  | -128 ÷ 127  | Shift colors from **yellow** to **blue**. |
+^ U-offset  | -128 ÷ 127  | Shift colors from **yellow** to **blue**. |
-^ V-offset  | -128 ÷ 127  | Shift colors from **green** to **red**. |
+^ V-offset  | -128 ÷ 127  | Shift colors from **green** to **red**. |
+For the **multiplier**: a value of **0** means a **zero** multiplier (horizonatl slope), **1024** means **1.0** (neutral multiplier), a value of **2048** means **2.0** multiplier.
+For the **offset shift**: a value of **-128** means **-50%** of the full range, a value of **+127** means **+50%** of the full range.
 Values for **Y**, **U** and **V** are unsigned integers in the range **0 ÷ 2048**, values for **Y-offset**, **U-offset** and **V-offset** are signed integers in the range **-128 ÷ +127**. Each YUV profile occupies **24 bytes** into the file.
@@ Line 193: / Line 196: @@
 ^ Group      ^ Contained in file            ^ Used for video modes  ^
-| 4K30/*     | adj_video_default_00_Imx377  | 4K@(25,30)  |
+| 4K30/*      | adj_video_default_00_Imx377  | 4K@(25,30)  |
-| 4K60/*     | adj_video_default_01_Imx377  | 4K@(50,60)  |
+| 4K60/*      | adj_video_default_01_Imx377  | 4K@(50,60)  |
-| FHD60/*    | adj_video_default_02_Imx377  | 4K@24,\\ 4K-Ultra@(24,30)\\ 2720x1520@(24,25,30,50,60)\\ 2560x1440@(24,25,30,50,60)\\ 1920x1080@(24,25,30,50,60)\\ 1920x1080-Ultra@(30,60)\\ Touchscreen operations  |
+| FHD60/*     | adj_video_default_02_Imx377  | 4K@24,\\ 4K-Ultra@(24,30)\\ 2720x1520@(24,25,30,50,60)\\ 2560x1440@(24,25,30,50,60)\\ 1920x1080@(24,25,30,50,60)\\ 1920x1080-Ultra@(30,60)\\ Touchscreen operations  |
-| FHD120/*   | adj_video_default_03_Imx377  | 1920x1080@120  |
+| FHD120/*    | adj_video_default_03_Imx377  | 1920x1080@120  |
-| 720@240/*  | adj_video_default_04_Imx377  | 1280×720@240  |
+| 720@240/*   | adj_video_default_04_Imx377  | 1280×720@240  |
+| 4K30Gyro/*  | adj_video_default_05_Imx377  | 4K@(25,30) with Gyro Stabilizer  |
 |                                                |||
 ^ Group           ^ Contained in file                 ^ Used for photo mode/ISO  ^
@@ Line 203: / Line 207: @@
 | Photo-Hi-ISO/*  | adj_hiso_still_default_00_Imx377  | Photo 800,1600,3200,6400\\ Photo Lapse 800,1600,3200,6400  |
-I have not found any video mode which is affected by tables contained into the file **adj_video_default_05_Imx377**, may be it affects some of the **non active video modes**?
+It seems rather crazy, but the tables contained into **adj_video_default_05_Imx377** are used only when **Gyro Stabilizer** is enabled and mode is **4K** at **25** or **30** fps.
 ==== How gamma curves are mixed together ====
@@ Line 428: / Line 433: @@
 {{.:ambarella:bitrateeditor-wb-presets.png?direct&640|}}
+FIXME: It is not know how this table works. It seems that labels are wrong: **YA_min** and **YB_min** are repeated twice, may be they are **YA_max** and **YB_max**.
+White balance is probably applied as a series of linear transformations to the **four raw values** captured by te **[[wp>Bayer_filter|Bayer filter sensor]]**. The four channels are **Red**, **Green-on-red**, **Blue** and **Green-on-blue**, each transformation consists of a multiplier coefficient (slope) and an offset.
+^ Gr  | Green on Red  |
+^ Gb  | Green on Blue  |
+^ Ya  | Y channel value of target image?  |
+^ Yb  | Y channel value of reference image?  |
 ===== 3D LUT tables =====
@@ Line 492: / Line 506: @@
   * **{{.:ambarella:h22-product-brief.pdf|Ambarella H22 Video SoC Overview}}**
   * **[[https://www.goprawn.com/forum/ambarella-cams/18473-color-correction-and-3d-lut-cube|Color correction and 3D LUT cube]]**
+  * **[[https://www.flir.it/support-center/iis/machine-vision/application-note/using-color-correction-in-blackfly-s/|Using Color Correction in Blackfly S and Oryx]]** - Local PDF: {{.:sjcam:color-correction-in-blackfly-s.pdf|color-correction-in-blackfly-s.pdf}}.