The patch number 14715 was added via Douglas Schilling Landgraf
<[email protected]>
to http://linuxtv.org/hg/v4l-dvb master development tree.
Kernel patches in this development tree may be modified to be backward
compatible with older kernels. Compatibility modifications will be
removed before inclusion into the mainstream Kernel
If anyone has any objections, please let us know by sending a message to:
Linux Media Mailing List <[email protected]>
------
From: Guennadi Liakhovetski <[email protected]>
sh_mobile_ceu_camera.c: update documentation to reflect the new cropping
Priority: normal
Signed-off-by: Guennadi Liakhovetski <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Signed-off-by: Douglas Schilling Landgraf <[email protected]>
---
linux/Documentation/video4linux/sh_mobile_ceu_camera.txt | 80 +++-------
1 file changed, 31 insertions(+), 49 deletions(-)
diff -r cd0065b40332 -r 281e4e865c12
linux/Documentation/video4linux/sh_mobile_ceu_camera.txt
--- a/linux/Documentation/video4linux/sh_mobile_ceu_camera.txt Tue May 11
02:22:52 2010 -0300
+++ b/linux/Documentation/video4linux/sh_mobile_ceu_camera.txt Tue May 11
02:24:40 2010 -0300
@@ -17,18 +17,18 @@
-2-- -\
| --\
| --\
-+-5-- -\ -- -3--
-| ---\
-| --- -4-- -\
-| -\
-| - -6--
++-5-- . -- -3-- -\
+| `... -\
+| `... -4-- . - -7..
+| `.
+| `. .6--
|
-| - -6'-
-| -/
-| --- -4'- -/
-| ---/
-+-5'- -/
-| -- -3'-
+| . .6'-
+| .´
+| ... -4'- .´
+| ...´ - -7'.
++-5'- .´ -/
+| -- -3'- -/
| --/
| --/
-2'- -/
@@ -36,7 +36,11 @@
|
-1'-
-Produced by user requests:
+In the above chart minuses and slashes represent "real" data amounts, points
and
+accents represent "useful" data, basically, CEU scaled amd 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))
@@ -106,52 +110,30 @@
S_CROP
------
-If old scale applied to new crop is invalid produce nearest new scale possible
+The API at http://v4l2spec.bytesex.org/spec/x1904.htm says:
-1. Calculate current combined scales.
+"...specification does not define an origin or units. However by convention
+drivers should horizontally count unscaled samples relative to 0H."
- scale_comb = (((4') - (4)) / ((6') - (6))) * (((2') - (2)) / ((3') -
(3)))
+We choose to follow the advise and interpret cropping units as client input
+pixels.
-2. Apply iterative sensor S_CROP for new input window.
+Cropping is performed in the following 6 steps:
-3. If old combined scales applied to new crop produce an impossible user
window,
-adjust scales to produce nearest possible window.
+1. Request exactly user rectangle from the sensor.
- width_u_out = ((5') - (5)) / scale_comb
+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.
- if (width_u_out > max)
- scale_comb = ((5') - (5)) / max;
- else if (width_u_out < min)
- scale_comb = ((5') - (5)) / min;
+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. Issue G_CROP to retrieve actual input window.
+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. Using actual input window and calculated combined scales calculate sensor
-target output window.
+5. Calculate and apply host scale = (6' - 6) / (4' - 4)
- 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.
+6. Calculate and apply host crop: 6 - 7 = (5 - 2) * (6' - 6) / (5' - 5)
--
Author: Guennadi Liakhovetski <[email protected]>
---
Patch is available at:
http://linuxtv.org/hg/v4l-dvb/rev/281e4e865c1246278468e62cfb90bd3e43a66e1b
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