Re: [PATCH v3] media: v4l2-ctrls: add control for dpcm predictor

[Prabhakar Lad <prabhakar.lad@ti.com>]

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@ti.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@ti.com>
>> Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
>> Cc: Sakari Ailus <sakari.ailus@iki.fi>
>> Cc: Hans Verkuil <hans.verkuil@cisco.com>
>> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
>> Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>> Cc: Rob Landley <rob@landley.net>
>> Cc: HeungJun Kim <riverful.kim@samsung.com>
> 
> Looks good.
> 
> Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.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
>