Implement Running Godot as Movie Writer

* Allows running the game in "movie writer" mode.
* It ensures entirely stable framerate, so your run can be saved stable and with proper sound (which is impossible if your CPU/GPU can't sustain doing this in real-time).
* If disabling vsync, it can save movies faster than the game is run, but if you want to control the interaction it can get difficult.
* Implements a simple, default MJPEG writer.

This new features has two main use cases, which have high demand:
* Saving game videos in high quality and ensuring the frame rate is *completely* stable, always.
* Using Godot as a tool to make movies and animations (which is ideal if you want interaction, or creating them procedurally. No other software is as good for this).

**Note**: This feature **IS NOT** for capturing real-time footage. Use something like OBS, SimpleScreenRecorder or FRAPS to achieve that, as they do a much better job at intercepting the compositor than Godot can probably do using Vulkan or OpenGL natively. If your game runs near real-time when capturing, you can still use this feature but it will play no sound (sound will be saved directly).

Usage:

$ godot --write-movie movie.avi [scene_file.tscn]

Missing:

* Options for configuring video writing via GLOBAL_DEF
* UI Menu for launching with this mode from the editor.
* Add to list of command line options.
* Add a feature tag to override configurations when movie writing (fantastic for saving videos with highest quality settings).

2 files changed, 5 insertions, 0 deletions

diff --git a/core/os/os.cpp b/core/os/os.cpp
index 327f1c95f2..93477f4288 100644
--- a/core/os/os.cpp
+++ b/core/os/os.cpp
@@ -388,6 +388,10 @@ bool OS::has_feature(const String &p_feature) {
 		return true;
 	}
 
+	if (p_feature == "movie") {
+		return _writing_movie;
+	}
+
 #ifdef DEBUG_ENABLED
 	if (p_feature == "debug") {
 		return true;
diff --git a/core/os/os.h b/core/os/os.h
index 157b8ab992..c6ea9d869a 100644
--- a/core/os/os.h
+++ b/core/os/os.h
@@ -58,6 +58,7 @@ class OS {
 	bool _allow_layered = false;
 	bool _stdout_enabled = true;
 	bool _stderr_enabled = true;
+	bool _writing_movie = false;
 
 	CompositeLogger *_logger = nullptr;