[PATCH v6] media: v4l2-ctrls: add control for dpcm predictor

From: Prabhakar Lad
Date: Mon Sep 10 2012 - 08:04:29 EST

From: Lad, Prabhakar <prabhakar.lad@xxxxxx>

add V4L2_CID_DPCM_PREDICTOR control of type menu, which
determines the dpcm predictor. The predictor can be either
simple or advanced.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@xxxxxx>
Signed-off-by: Manjunath Hadli <manjunath.hadli@xxxxxx>
Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Acked-by: Sakari Ailus <sakari.ailus@xxxxxx>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Rob Landley <rob@xxxxxxxxxxx>
---
This patches has one checkpatch warning for line over
80 characters altough it can be avoided I have kept it
for consistency.

Changes for v6:
1: Fitted the description within 80 characters per line,
pointed by Sakari.

Changes for v5:
1: Changed the control's name to 'Simple' and 'Advanced'
as pointed by Sakari.
2: Changed the description of DPCM. Thanks to Sakari for
providing the description.

Changes for v4:
1: Aligned the description to fit appropriately in the
para tag, pointed by Sylwester.

Changes for v3:
1: Added better explanation for DPCM, pointed by Hans.

Changes for v2:
1: Added documentaion in controls.xml pointed by Sylwester.
2: Chnaged V4L2_DPCM_PREDICTOR_ADVANCE to V4L2_DPCM_PREDICTOR_ADVANCED
pointed by Sakari.

Documentation/DocBook/media/v4l/controls.xml | 48 +++++++++++++++++++++++++-
drivers/media/v4l2-core/v4l2-ctrls.c | 9 +++++
include/linux/videodev2.h | 5 +++
3 files changed, 61 insertions(+), 1 deletions(-)

diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
index 93b9c68..f0fb08d 100644
--- a/Documentation/DocBook/media/v4l/controls.xml
+++ b/Documentation/DocBook/media/v4l/controls.xml
@@ -4267,7 +4267,53 @@ interface and may change in the future.</para>
pixels / second.
</entry>
</row>
- <row><entry></entry></row>
+ <row>
+ <entry spanname="id">
+ <constant>V4L2_CID_DPCM_PREDICTOR</constant>
+ </entry>
+ <entry>menu</entry>
+ </row>
+ <row id="v4l2-dpcm-predictor">
+ <entry spanname="descr"> Differential pulse-code modulation (DPCM)
+ compression can be used to compress the samples into fewer bits
+ than they would otherwise require. This is done by calculating the
+ difference between consecutive samples and outputting the
+ difference which in average is much smaller than the values of the
+ samples themselves since there is generally lots of correlation
+ between adjacent pixels. In decompression the original samples are
+ reconstructed. The process isn't lossless as the encoded sample
+ size in bits is less than the original.
+
+ <para>Formats using DPCM compression include
+ <xref linkend="pixfmt-srggb10dpcm8" />.</para>
+
+ <para>This control is used to select the predictor used to encode
+ the samples.</para>
+
+ <para>The main difference between the simple and the advanced
+ predictors is image quality, with advanced predictor supposed to
+ produce better quality images as a result. Simple predictor can be
+ used e.g. for testing purposes. For more information about DPCM see
+ <ulink url=
+ "http://en.wikipedia.org/wiki/Differential_pulse-code_modulation";>
+ Wikipedia</ulink>.</para>
+ </entry>
+ </row>
+ <row>
+ <entrytbl spanname="descr" cols="2">
+ <tbody valign="top">
+ <row>
+ <entry><constant>V4L2_DPCM_PREDICTOR_SIMPLE</constant></entry>
+ <entry>Predictor type is simple</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_DPCM_PREDICTOR_ADVANCED</constant></entry>
+ <entry>Predictor type is advanced</entry>
+ </row>
+ </tbody>
+ </entrytbl>
+ </row>
+ <row><entry></entry></row>
</tbody>
</tgroup>
</table>
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index b6a2ee7..8f2f40b 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -425,6 +425,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
"Gray",
NULL,
};
+ static const char * const dpcm_predictor[] = {
+ "Simple",
+ "Advanced",
+ NULL,
+ };

switch (id) {
case V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ:
@@ -502,6 +507,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
return mpeg4_profile;
case V4L2_CID_JPEG_CHROMA_SUBSAMPLING:
return jpeg_chroma_subsampling;
+ case V4L2_CID_DPCM_PREDICTOR:
+ return dpcm_predictor;

default:
return NULL;
@@ -732,6 +739,7 @@ const char *v4l2_ctrl_get_name(u32 id)
case V4L2_CID_IMAGE_PROC_CLASS: return "Image Processing Controls";
case V4L2_CID_LINK_FREQ: return "Link Frequency";
case V4L2_CID_PIXEL_RATE: return "Pixel Rate";
+ case V4L2_CID_DPCM_PREDICTOR: return "DPCM Predictor";

default:
return NULL;
@@ -832,6 +840,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
case V4L2_CID_ISO_SENSITIVITY_AUTO:
case V4L2_CID_EXPOSURE_METERING:
case V4L2_CID_SCENE_MODE:
+ case V4L2_CID_DPCM_PREDICTOR:
*type = V4L2_CTRL_TYPE_MENU;
break;
case V4L2_CID_LINK_FREQ:
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index 6d6dfa7..ca9fb78 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -2000,6 +2000,11 @@ enum v4l2_jpeg_chroma_subsampling {

#define V4L2_CID_LINK_FREQ (V4L2_CID_IMAGE_PROC_CLASS_BASE + 1)
#define V4L2_CID_PIXEL_RATE (V4L2_CID_IMAGE_PROC_CLASS_BASE + 2)
+#define V4L2_CID_DPCM_PREDICTOR (V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
+enum v4l2_dpcm_predictor {
+ V4L2_DPCM_PREDICTOR_SIMPLE = 0,
+ V4L2_DPCM_PREDICTOR_ADVANCED = 1,
+};

/*
* T U N I N G
--
1.7.0.4

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