This moves some functions that are generic to a separate source
file. While doing so the api to those functions was improved to
be more generic and not depend on knowledge about the internal
structure of the plugin.
Those functions are actually causing more problems than
helping out with the preview because the width/height is
updated immediately while the actual size of the frames
displayed changes later.
Due to the plugin creating a thread to retrieve and output the
captured image data, care must taken to not modify data the
thread reads from the outside while the thread is running.
In previous revisions some settings accessed by the capture
thread were written to in the update function which could cause
image corruption and in the worst case crashes.
The members of the data struct are now split into two groups,
those that are used by the thread while it is running and must
not be changed from the outside, and those can be changed at any
time.
This adds a function to prepare the source_frame struct for use
with obs_source_output_video. Since all of the values except for
the timestamp and data pointers are known in before it makes
little sense to compute them over and over again.
Due to the fact that v4l2 uses a single continuous memory segment
for multi planar formats we can also precompute memory offsets for
the planes.
By using the wrapper functions supplied by libv4l2 we gain
support for formats not natively supported by obs.
The library intercepts certain system calls to transparently
enable recoding.
Until a proper fix is found to support devices that use stepwise
or continuous values for framesize and framerate this adds fixed
values that can be selected.
For devices that support discrete values those are still queried
and used.
The locale parameter was a mistake, because it puts extra needless
burden upon the module developer to have to handle this variable for
each and every single callback function. The parameter is being removed
in favor of a single centralized module callback function that
specifically updates locale information for a module only when needed.
Having the value stored here is somewhat pointless, so this is one step
in fixing the locale handling. Locale should be handled by the modules
themselves with their own loaded locale lookup information.