Hi Laurent,
Laurent Pinchart wrote:
On Tuesday 10 January 2012 10:52:26 Sakari Ailus wrote:
Laurent Pinchart wrote:
On Tuesday 10 January 2012 10:42:58 Sakari Ailus wrote:
Laurent Pinchart wrote:
On Tuesday 10 January 2012 00:26:46 Sakari Ailus wrote:
Laurent Pinchart wrote:
On Monday 09 January 2012 23:32:06 Sakari Ailus wrote:
Laurent Pinchart wrote:
On Monday 09 January 2012 18:38:25 Sakari Ailus wrote:
...
A fourth section may be required as well: at this level the frame
rate (or frame time) range makes more sense than the low-level
blanking values. The blanking values can be calculated from the
frame time and a flag which tells whether either horizontal or
vertical blanking should be preferred.
How does one typically select between horizontal and vertical
blanking ? Do mixed modes make sense ?
There are minimums and maximums for both. You can increase the frame
time by increasing value for either or both of them --- to achieve
very long frame times you may have to use both, but that's not very
common in practice. I think we should have a flag to tell which one
should be increased first --- the effect would be to have the
minimum possible value on the other.
But how do you decide in practice which one to increase when you're
an application (or middleware) developer ?
I think it's the responsibility of this library to do that, unless the
user wants really, really precise control in which case they have to
deal with the blanking values directly. In general it should be the
library.
And how does the library decide ? :-)
frame_time = pixel_rate / ((width + hblank) * (height + vblank))
The user gives you frame time and the configuration contains the
information which one to prefer. Let's say the user prefers hblank (from
the above):
That was my question, how does the user decide whether hblank or vblank
is preferred ?
I think that should be defined in the configuration itself. It's very
unlikely there's any need to change this dynamically.
Sure, but that's not my point. How does the user decide in the first place
when writing the configuration ?
That's a policy decision. There may be multiple reasons for that, but
the most obvious I can think of is a decision between amortised memory
access rate and the rolling shutter effect. There may be other factors
like time of year, phase of moon and colour of the neighbour's cat to
name a few. :-)
It might also make sense to be able to specify a minimum for horizontal
blanking which is bigger than the minimum the sensor allows. But that's
going to the fine details.
--
Sakari Ailus
sakari.ailus@xxxxxx
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