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

Commit Message

Prabhakar Lad Sept. 10, 2012, 12:03 p.m. UTC

From: Lad, Prabhakar <[e-mail]>

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 <[e-mail]>
Signed-off-by: Manjunath Hadli <[e-mail]>
Acked-by: Hans Verkuil <[e-mail]>
Acked-by: Sakari Ailus <[e-mail]>
Reviewed-by: Sylwester Nawrocki <[e-mail]>
Cc: Laurent Pinchart <[e-mail]>
Cc: Mauro Carvalho Chehab <[e-mail]>
Cc: Hans de Goede <[e-mail]>
Cc: Kyungmin Park <[e-mail]>
Cc: Rob Landley <[e-mail]>
---
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(-)

Patch

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