Hi Hans and Prabhakar,
Hans Verkuil wrote:
Hi Prabhakar!
I've got some documentation review comments below...
On Thu August 30 2012 00:58:16 Prabhakar Lad wrote:
From: Lad, Prabhakar <prabhakar....@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....@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.ha...@ti.com>
Cc: Sakari Ailus <sakari.ai...@iki.fi>
Cc: Hans Verkuil <hans.verk...@cisco.com>
Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
Cc: Mauro Carvalho Chehab <mche...@infradead.org>
Cc: Sylwester Nawrocki <s.nawro...@samsung.com>
Cc: Hans de Goede <hdego...@redhat.com>
Cc: Kyungmin Park <kyungmin.p...@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 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 | 25 ++++++++++++++++++++++++-
drivers/media/v4l2-core/v4l2-ctrls.c | 9 +++++++++
include/linux/videodev2.h | 5 +++++
3 files changed, 38 insertions(+), 1 deletions(-)
diff --git a/Documentation/DocBook/media/v4l/controls.xml
b/Documentation/DocBook/media/v4l/controls.xml
index 93b9c68..84746d0 100644
--- a/Documentation/DocBook/media/v4l/controls.xml
+++ b/Documentation/DocBook/media/v4l/controls.xml
@@ -4267,7 +4267,30 @@ 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"> DPCM Predictor: depicts what type of
prediction
+ is used simple or advanced.
This is not useful information. It basically just rephrases the name of the
define without actually telling me anything.
I would expect to see here at least the following:
- what the DPCM abbreviation stands for
- a link or bibliography reference to the relevant standard (if there is any)
There's a Wikipedia article:
<URL:http://en.wikipedia.org/wiki/Differential_pulse-code_modulation>
It's the same DPCM encoding as in many of the compressed raw bayer formats.
- a high-level explanation of what this do and what the difference is between
simple and advanced.
That's somewhat subjective and hardware dependent. If I understand this
correctly, the "advanced" should differ only quality-wise from "simple"
option. Why one would use "simple" instead of "advanced" then? Perhaps
mostly for testing purposes; it might be that the advanced predictor
could have issues in certain cases where the simple would not. However
this isn't the only piece of hardware where I see that this is
configurable, and the simple one was even the default.
If this is part of a video compression standard, then this control would
probably
belong to the MPEG control class as well.
It's not --- DPCM compression is typically used on the bus between the
sensor and the receiver to compress the data as the bus is often a
limiting factor in the transfer rate. DPCM compression can be used to
squeeze the data from 10 to 8 bits without much loss in quality or
dynamic range.
Cheers,
--
Sakari Ailus
sakari.ai...@iki.fi
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
