Since the helper function also needs to pack/unpack the resolution, the
pack/unpack functions were moved to the helper library and prefixed with
v4l2_ in order to avoid possible collisions.

This was added at a time where the source properties dialog did not
pop up automatically on source creation. Now when the properties are
displayed the first device in the select input will be selected by
default if there was none already specified by the source settings.

This will make the code cleaner and also save one redundant round of
device enumeration.

The capabilities flags that were used previously describe all
capabilities the physical device offers. This would cause devices
that are accessible through multiple device nodes to show up with
all device nodes while only one of the nodes might actually offer
the needed video capture capability.

If the device has more nodes the CAP_DEVICES_CAP flag might be set
in which case the device_caps field is filled with the capabilities
that only apply to that specific node that is opened.

When initialization of the device fails the plugin may hang
trying to join a non-existing pthread.

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.

This adds an additional property to the plugin to select
an input if the device has multiple ones.

Changed:                 To:
-----------------------------------------------
obs_data_getjson         obs_data_get_json
obs_data_getstring       obs_data_get_string
obs_data_getint          obs_data_get_int
obs_data_getdouble       obs_data_get_double
obs_data_getbool         obs_data_get_bool
obs_data_getobj          obs_data_get_obj
obs_data_getarray        obs_data_get_array
obs_data_setstring       obs_data_set_string
obs_data_setint          obs_data_set_int
obs_data_setdouble       obs_data_set_double
obs_data_setbool         obs_data_set_bool
obs_data_setobj          obs_data_set_obj
obs_data_setarray        obs_data_set_array
obs_data_item_getstring  obs_data_item_get_string
obs_data_item_getint     obs_data_item_get_int
obs_data_item_getdouble  obs_data_item_get_double
obs_data_item_getbool    obs_data_item_get_bool
obs_data_item_getobj     obs_data_item_get_obj
obs_data_item_getarray   obs_data_item_get_array
obs_data_item_setstring  obs_data_item_set_string
obs_data_item_setint     obs_data_item_set_int
obs_data_item_setdouble  obs_data_item_set_double
obs_data_item_setbool    obs_data_item_set_bool
obs_data_item_setobj     obs_data_item_set_obj
obs_data_item_setarray   obs_data_item_set_array

Renamed:                       To:
-------------------------------------------------------
obs_source_info::defaults       obs_source_info::get_defaults
obs_source_info::properties     obs_source_info::get_properties
obs_output_info::defaults       obs_output_info::get_defaults
obs_output_info::properties     obs_output_info::get_properties
obs_output_info::total_bytes    obs_output_info::get_total_bytes
obs_output_info::dropped_frames obs_output_info::get_dropped_frames
obs_encoder_info::defaults      obs_encoder_info::get_defaults
obs_encoder_info::properties    obs_encoder_info::get_properties
obs_encoder_info::extra_data    obs_encoder_info::get_extra_data
obs_encoder_info::sei_data      obs_encoder_info::get_sei_data
obs_encoder_info::audio_info    obs_encoder_info::get_audio_info
obs_encoder_info::video_info    obs_encoder_info::get_video_fino
obs_service_info::defaults      obs_service_info::get_defaults
obs_service_info::properties    obs_service_info::get_properties

Renamed:                    To:
-------------------------------------------------------
obs_source_info::getname    obs_source_info::get_name
obs_source_info::getwidth   obs_source_info::get_width
obs_source_info::getheight  obs_source_info::get_height
obs_output_info::getname    obs_output_info::get_name
obs_encoder_info::getname   obs_encoder_info::get_name
obs_service_info::getname   obs_service_info::get_name

For the sake of naming consistency with the rest of obs.h, prefix this
structure and associated functions with obs_.

Renamed structures:
- struct source_frame (now obs_source_frame)

Renamed functions:
- source_frame_init (now obs_source_frame_init)
- source_frame_free (now obs_source_frame_free)
- source_frame_create (now obs_source_frame_create)
- source_frame_destroy (now obs_source_frame_destroy)

Affected functions:
- obs_source_output_video
- obs_source_get_frame
- obs_source_release_frame

This adds some documentation to the mmap functions and also
improves the logging by bumping errors to LOG_ERROR.

This should save a little bit of memory memory.

This adds some documentation to the update function and also
improves the logging by adding some info and bumping errors
to LOG_ERROR.

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.

The data provided by v4l2 for multiplanar formats is one
consecutive block that just needs to be splitted for obs.

Formats that are emulated by v4l2 are marked by appending
"(Emulated)" to them.

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.

This adds some mostly user focused logging statements.

Small code changes to decrease indentation a little.

With no device present the capability callbacks would cause an
infinite loop.

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.

added ability to choose device, pixel format, resolution
and frame rate

This patch adds a plugin to capture video data from v4l2 devices under linux.