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Message-ID: <50447A5C.8040401@ti.com>
Date: Mon, 3 Sep 2012 15:07:32 +0530
From: Prabhakar Lad <prabhakar.lad@...com>
To: Sylwester Nawrocki <s.nawrocki@...sung.com>
CC: LMML <linux-media@...r.kernel.org>,
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>, Sakari Ailus <sakari.ailus@....fi>,
Hans Verkuil <hans.verkuil@...co.com>,
Mauro Carvalho Chehab <mchehab@...radead.org>,
Hans de Goede <hdegoede@...hat.com>,
Kyungmin Park <kyungmin.park@...sung.com>,
Rob Landley <rob@...dley.net>
Subject: Re: [PATCH v3] media: v4l2-ctrls: add control for dpcm predictor
Hi Sylwester,
Thanks for the review.
On Monday 03 September 2012 02:51 PM, Sylwester Nawrocki wrote:
> On 09/03/2012 09:20 AM, Prabhakar Lad wrote:
>> 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>
>
> Looks good.
>
> Reviewed-by: Sylwester Nawrocki <s.nawrocki@...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>
>
> nit: this whole paragraph could fit in 2 lines.
>
thanks for the catch ,I'll post a v4 fixing this.
Thanks and Regards,
--Prabhakar Lad
>> +
>> + <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
>
> Regards,
> Sylwester
>
--
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