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Diffstat (limited to 'Documentation/video4linux/sh_mobile_ceu_camera.txt')
| -rw-r--r-- | Documentation/video4linux/sh_mobile_ceu_camera.txt | 139 |
1 files changed, 0 insertions, 139 deletions
diff --git a/Documentation/video4linux/sh_mobile_ceu_camera.txt b/Documentation/video4linux/sh_mobile_ceu_camera.txt deleted file mode 100644 index 1e96ce6e2..000000000 --- a/Documentation/video4linux/sh_mobile_ceu_camera.txt +++ /dev/null @@ -1,139 +0,0 @@ - Cropping and Scaling algorithm, used in the sh_mobile_ceu_camera driver - ======================================================================= - -Terminology ------------ - -sensor scales: horizontal and vertical scales, configured by the sensor driver -host scales: -"- host driver -combined scales: sensor_scale * host_scale - - -Generic scaling / cropping scheme ---------------------------------- - --1-- -| --2-- -\ -| --\ -| --\ -+-5-- . -- -3-- -\ -| `... -\ -| `... -4-- . - -7.. -| `. -| `. .6-- -| -| . .6'- -| .´ -| ... -4'- .´ -| ...´ - -7'. -+-5'- .´ -/ -| -- -3'- -/ -| --/ -| --/ --2'- -/ -| -| --1'- - -In the above chart minuses and slashes represent "real" data amounts, points and -accents represent "useful" data, basically, CEU scaled and cropped output, -mapped back onto the client's source plane. - -Such a configuration can be produced by user requests: - -S_CROP(left / top = (5) - (1), width / height = (5') - (5)) -S_FMT(width / height = (6') - (6)) - -Here: - -(1) to (1') - whole max width or height -(1) to (2) - sensor cropped left or top -(2) to (2') - sensor cropped width or height -(3) to (3') - sensor scale -(3) to (4) - CEU cropped left or top -(4) to (4') - CEU cropped width or height -(5) to (5') - reverse sensor scale applied to CEU cropped width or height -(2) to (5) - reverse sensor scale applied to CEU cropped left or top -(6) to (6') - CEU scale - user window - - -S_FMT ------ - -Do not touch input rectangle - it is already optimal. - -1. Calculate current sensor scales: - - scale_s = ((2') - (2)) / ((3') - (3)) - -2. Calculate "effective" input crop (sensor subwindow) - CEU crop scaled back at -current sensor scales onto input window - this is user S_CROP: - - width_u = (5') - (5) = ((4') - (4)) * scale_s - -3. Calculate new combined scales from "effective" input window to requested user -window: - - scale_comb = width_u / ((6') - (6)) - -4. Calculate sensor output window by applying combined scales to real input -window: - - width_s_out = ((7') - (7)) = ((2') - (2)) / scale_comb - -5. Apply iterative sensor S_FMT for sensor output window. - - subdev->video_ops->s_fmt(.width = width_s_out) - -6. Retrieve sensor output window (g_fmt) - -7. Calculate new sensor scales: - - scale_s_new = ((3')_new - (3)_new) / ((2') - (2)) - -8. Calculate new CEU crop - apply sensor scales to previously calculated -"effective" crop: - - width_ceu = (4')_new - (4)_new = width_u / scale_s_new - left_ceu = (4)_new - (3)_new = ((5) - (2)) / scale_s_new - -9. Use CEU cropping to crop to the new window: - - ceu_crop(.width = width_ceu, .left = left_ceu) - -10. Use CEU scaling to scale to the requested user window: - - scale_ceu = width_ceu / width - - -S_CROP ------- - -The API at http://v4l2spec.bytesex.org/spec/x1904.htm says: - -"...specification does not define an origin or units. However by convention -drivers should horizontally count unscaled samples relative to 0H." - -We choose to follow the advise and interpret cropping units as client input -pixels. - -Cropping is performed in the following 6 steps: - -1. Request exactly user rectangle from the sensor. - -2. If smaller - iterate until a larger one is obtained. Result: sensor cropped - to 2 : 2', target crop 5 : 5', current output format 6' - 6. - -3. In the previous step the sensor has tried to preserve its output frame as - good as possible, but it could have changed. Retrieve it again. - -4. Sensor scaled to 3 : 3'. Sensor's scale is (2' - 2) / (3' - 3). Calculate - intermediate window: 4' - 4 = (5' - 5) * (3' - 3) / (2' - 2) - -5. Calculate and apply host scale = (6' - 6) / (4' - 4) - -6. Calculate and apply host crop: 6 - 7 = (5 - 2) * (6' - 6) / (5' - 5) - --- -Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de> |