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Date: Mon, 3 Sep 2012 12:50:51 +0530
From: Prabhakar Lad <prabhakar.lad@...com>
To: LMML <linux-media@...r.kernel.org>
CC: dlos <davinci-linux-open-source@...ux.davincidsp.com>,
<linux-kernel@...r.kernel.org>,
Manjunath Hadli <manjunath.hadli@...com>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
<linux-doc@...r.kernel.org>,
"Lad, Prabhakar" <prabhakar.lad@...com>,
Sakari Ailus <sakari.ailus@....fi>,
Hans Verkuil <hans.verkuil@...co.com>,
Mauro Carvalho Chehab <mchehab@...radead.org>,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
Hans de Goede <hdegoede@...hat.com>,
Kyungmin Park <kyungmin.park@...sung.com>,
Rob Landley <rob@...dley.net>,
HeungJun Kim <riverful.kim@...sung.com>
Subject: [PATCH v3] media: v4l2-ctrls: add control for dpcm predictor
From: Lad, Prabhakar <prabhakar.lad@...com>
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@...com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@...com>
Cc: Sakari Ailus <sakari.ailus@....fi>
Cc: Hans Verkuil <hans.verkuil@...co.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...radead.org>
Cc: Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc: Hans de Goede <hdegoede@...hat.com>
Cc: Kyungmin Park <kyungmin.park@...sung.com>
Cc: Rob Landley <rob@...dley.net>
Cc: HeungJun Kim <riverful.kim@...sung.com>
---
This patches has one checkpatch warning for line over
80 characters altough it can be avoided I have kept it
for consistency.
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..f704218 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) 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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