mirror of
https://github.com/torvalds/linux.git
synced 2024-12-13 22:53:20 +00:00
35b23b5226
The sh_mobile_ceu_camera driver implements an advanced algorithm, combining scaling and cropping on the client and on the host. Due to its complexity the algorithm deserves separate documentation. create mode 100644 Documentation/video4linux/sh_mobile_ceu_camera.txt Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
158 lines
3.8 KiB
Plaintext
158 lines
3.8 KiB
Plaintext
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-- -\
|
|
| -\
|
|
| - -6--
|
|
|
|
|
| - -6'-
|
|
| -/
|
|
| --- -4'- -/
|
|
| ---/
|
|
+-5'- -/
|
|
| -- -3'-
|
|
| --/
|
|
| --/
|
|
-2'- -/
|
|
|
|
|
|
|
|
-1'-
|
|
|
|
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 = ((3') - (3)) / ((2') - (2))
|
|
|
|
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 = ((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
|
|
------
|
|
|
|
If old scale applied to new crop is invalid produce nearest new scale possible
|
|
|
|
1. Calculate current combined scales.
|
|
|
|
scale_comb = (((4') - (4)) / ((6') - (6))) * (((2') - (2)) / ((3') - (3)))
|
|
|
|
2. Apply iterative sensor S_CROP for new input window.
|
|
|
|
3. If old combined scales applied to new crop produce an impossible user window,
|
|
adjust scales to produce nearest possible window.
|
|
|
|
width_u_out = ((5') - (5)) / scale_comb
|
|
|
|
if (width_u_out > max)
|
|
scale_comb = ((5') - (5)) / max;
|
|
else if (width_u_out < min)
|
|
scale_comb = ((5') - (5)) / min;
|
|
|
|
4. Issue G_CROP to retrieve actual input window.
|
|
|
|
5. Using actual input window and calculated combined scales calculate sensor
|
|
target output window.
|
|
|
|
width_s_out = ((3') - (3)) = ((2') - (2)) / scale_comb
|
|
|
|
6. Apply iterative S_FMT for new sensor target output window.
|
|
|
|
7. Issue G_FMT to retrieve the actual sensor output window.
|
|
|
|
8. Calculate sensor scales.
|
|
|
|
scale_s = ((3') - (3)) / ((2') - (2))
|
|
|
|
9. Calculate sensor output subwindow to be cropped on CEU by applying sensor
|
|
scales to the requested window.
|
|
|
|
width_ceu = ((5') - (5)) / scale_s
|
|
|
|
10. Use CEU cropping for above calculated window.
|
|
|
|
11. Calculate CEU scales from sensor scales from results of (10) and user window
|
|
from (3)
|
|
|
|
scale_ceu = calc_scale(((5') - (5)), &width_u_out)
|
|
|
|
12. Apply CEU scales.
|
|
|
|
--
|
|
Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
|