[PATCH v4] media: v4l2-ctrls: add control for dpcm predictor

From: Prabhakar Lad
Date: Tue Sep 04 2012 - 01:38:52 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>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
Cc: Sakari Ailus <sakari.ailus@xxxxxx>
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 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 | 46 +++++++++++++++++++++++++-
drivers/media/v4l2-core/v4l2-ctrls.c | 9 +++++
include/linux/videodev2.h | 5 +++
3 files changed, 59 insertions(+), 1 deletions(-)

diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
index 93b9c68..ad873ea 100644
--- a/Documentation/DocBook/media/v4l/controls.xml
+++ b/Documentation/DocBook/media/v4l/controls.xml
@@ -4267,7 +4267,51 @@ 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) is a signal
+ encoder that uses the baseline of pulse-code modulation (PCM) but adds some
+ functionalities based on the prediction of the samples of the signal. The input
+ can be an analog signal or a digital signal.
+
+ <para>If the input is a continuous-time analog signal, it needs to be sampled
+ first so that a discrete-time signal is the input to the DPCM encoder.</para>
+
+ <para>Simple: take the values of two consecutive samples; if they are analog
+ samples, quantize them; calculate the difference between the first one and the
+ next; the output is the difference, and it can be further entropy coded.</para>
+
+ <para>Advanced: instead of taking a difference relative to a previous input sample,
+ take the difference relative to the output of a local model of the decoder process;
+ in this option, the difference can be quantized, which allows a good way to
+ incorporate a controlled loss in the encoding.</para>
+
+ <para>Applying one of these two processes, short-term redundancy (positive correlation of
+ nearby values) of the signal is eliminated; compression ratios on the order of 2 to 4
+ can be achieved if differences are subsequently entropy coded, because the entropy of
+ the difference signal is much smaller than that of the original discrete signal treated
+ as independent samples.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..2d7bc15 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 Predictor",
+ "Advanced Predictor",
+ 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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