Seems that most decoders that don't read the h264 header tend to expect
601 instead of 709.

For game capture, if a game is running at for example 800 FPS and limit
capture framerate is off, it would try to capture all 800 of those
frames, dramatically reducing performance more than what would ever be
necessary.

When limit capture framerate is off, instead of capturing all frames,
capture frames at an interval of twice the OBS FPS, identical to how
OBS1 works by default.  This should greatly increase performance under
that circumstance.

Use the actual parameter from the x264 params for CRF, and also make
sure to specify that CRF is meant to be 0 if CBR is enabled.

Sets the color range/space for FFmpeg output encoders that support it.

This also adds the ability to detect whether it stopped due to lack of
space or not -- particularly useful for the FFmpeg output due to
lossless file format support.

For the FFmpeg output, the encoder ids are sort of superfluous.  They
really should be optional.  If they're not set, it should use the
encoder name string instead to determine the ids automatically.

It seems that certain encoders (quicksync) do not have proper back-end
support in the windows media foundation libraries for certain CPUs.
Quicksync doesn't appear to support CPUs that are not haswell (4xxx) or
above.  It's really annoying, but there's not much we can do about it
until we implement our own custom quicksync implementation.

This check simply makes it attempt to spawn an encoder to check to see
whether the encoder can actually be created before registering an
encoder.

It's not impossible that this sort of thing could happen, although
unlikely.

The encoders were stopping before processing was completed, which could
cause the output to access data that's potentially invalidated.

The previous commit (672378d2) was supposed to fix issues with the
encoder releasing while data was still being processed, but did not
account for when the encoder has never started up.  That was my fault.

Furthermore, the way in which it was waiting to drain events was
incorrect.  The encoder may still be active even though there aren't any
events queued.  The proper way to wait for an async encoder to finish up
is to process output samples until it requests more input samples.

After I made it so that the encoder internal data gets destroyed when
all outputs stop using it (fa7286f8), the media foundation h264 encoder
started having crashes on shutdown.  After a lot of testing, I realized
that the reason it started happening is almost assuredly because active
encoding events had not yet been completed.

After making it wait on those events by calling DrainEvents(true), the
crashes stopped.  So asynchronous actions were clearly still occurring
and it was shutting down while data was still being processed, thus
leading to a crash.

Clean up Intensity Pro 4K commit a bit

Adds a VideoToolbox based H264 encoder for OSX, which most notably
allows the use of hardware encoding (Quicksync).

NOTES:
- Hardware encoding is handled by Apple itself internally.  The plugin
  itself has little control over many details due to the way that Apple
  designed the VideoToolbox interface.  Generally however, quicksync is
  used if available on the CPU, and quicksync is almost always available
  due to the fact that macs are exclusively Intel.

- The VideoToolbox does not seem to implement CBR, so it won't be
  available.  These encoders are generally not recommended for
  streaming.

Implements hardware encoders through the Media Foundation interface
provided by Microsoft.

Supports:
- Quicksync (Intel)
- VCE (AMD)
- NVENC (NVIDIA, might only be supported through MF on Windows 10)

Notes:
- NVENC and VCE do not appear to have proper CBR implementations.  This
  isn't a fault of our code, but the Media Foundation libraries.
  Quicksync however appears to be fine.

API changed from:
obs_source_info::get_name(void)
obs_output_info::get_name(void)
obs_encoder_info::get_name(void)
obs_service_info::get_name(void)

API changed to:
obs_source_info::get_name(void *type_data)
obs_output_info::get_name(void *type_data)
obs_encoder_info::get_name(void *type_data)
obs_service_info::get_name(void *type_data)

This allows the type data to be used when getting the name of the
object (useful for plugin wrappers primarily).

NOTE: Though a parameter was added, this is backward-compatible with
older plugins due to calling convention.  The new parameter will simply
be ignored by older plugins, and the stack (if used) will be cleaned up
by the caller.

The private type data is the type_data variable that's provided when
object types are registered by plugins.

This is useful for allowing the ability to have private data associated
with the object type definition structures.  This private data can be
useful for things like plugin wrappers for other languages, or providing
dynamically generated object types.

Selecting any supported FFmpeg format where ff_format_desc_extensions
returns NULL would crash the std::string constructor, so we pass an
empty extension instead (rtsp is one candidate format that triggers
the crash, on my machine at least)

This allows changing e.g. the number of segments in a hls playlist and
its caching behavior with:
"hls_allow_cache=1 hls_list_size=0"

This is used by some muxers that set AVFMT_NOFILE and doesn't seem to
hurt muxers that don't set it; notable this makes the hls muxer output
its m3u8 playlist with the proper filename in the proper directory

cleaning up my previous commit a bit. we can just keep the
appropriate BMDPixelFormat as a data member and keep StartCapture() a
bit clearer.

this might also be helpful if (when?) the detection code needs to be
more robust or configurable

Capture BMI Intensity Pro 4K video

detect the device type when initializing the device instance and
determine whether to capture YUV or RGB. tested with a Blackmagic
Intensity Pro and a Blackmagic Intensity Pro 4K in the same machine,
capturing at the same time, on Linux

This prevents encoders (hardware encoders in particular) from being
continually active when all outputs disconnect from an encoder.  This is
mostly just a temporary measure; the encoding interface may need a bit
of a redesign.  It will also definitely needs to be able to flush at
some point.  Currently when an output is stopped, the pending data is
discarded, which needs to be fixed.

Allows objects to be created regardless of whether the actual id exists
or not.  This is a precaution that preserves objects/settings if for
some reason the id was removed for whatever reason (plugin removed, or
hardware encoder that disappeared).  This was already added for sources,
but really needs to be added for other libobs objects as well: outputs,
encoders, services.

If the FFMPEG_AVCODEC_LIBRARIES variable does not exist, it will
generate a cmake error, so check to make sure the variable exists before
executing this code.

This fixes the compile error: "'AVDISCARD_NONINTRA' undeclared" when
using a libavcodec version earlier than 55.67.100.

Closes jp9000/obs-studio#469

These fucntions prevent the computer from going to sleep, hibernating,
or starting up a screen saver.

On linux, it will also attempt to use DBus to prevent gnome/kde/etc
sleep, but it's not necessarily required in order to compile the
library.  Otherwise, it will simply call "xdg-screensaver reset" once
every 30 seconds to reset the screensaver timer.

The DBus library is a message bus system used to make applications
communicate with each other.  The primary reason for adding it is to
access certain service features to prevent computer sleep/hibernate/etc.

This will also create a HAVE_DBUS variable (set to 1 or 0 if found or
not found)

The user may not want their audio or their display to be captured when
creating a new scene collection.  Make new scene collections default to
fully empty.

For the sake of consistency, always create a display capture source on
the very first run of the program, just to have something displayed.

(NOTE: The only exception here is on windows 7/vista, which isn't ideal
for display capture, so it'll continue to be left blank)