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).

4 files changed, 86 insertions, 6 deletions

diff --git a/doc/classes/@GlobalScope.xml b/doc/classes/@GlobalScope.xml
index 18ea29857b..fed6270247 100644
--- a/doc/classes/@GlobalScope.xml
+++ b/doc/classes/@GlobalScope.xml
@@ -2512,19 +2512,21 @@
 		</constant>
 		<constant name="PROPERTY_HINT_SAVE_FILE" value="38" enum="PropertyHint">
 		</constant>
-		<constant name="PROPERTY_HINT_INT_IS_OBJECTID" value="39" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_GLOBAL_SAVE_FILE" value="39" enum="PropertyHint">
 		</constant>
-		<constant name="PROPERTY_HINT_INT_IS_POINTER" value="41" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_INT_IS_OBJECTID" value="40" enum="PropertyHint">
 		</constant>
-		<constant name="PROPERTY_HINT_ARRAY_TYPE" value="40" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_INT_IS_POINTER" value="42" enum="PropertyHint">
 		</constant>
-		<constant name="PROPERTY_HINT_LOCALE_ID" value="42" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_ARRAY_TYPE" value="41" enum="PropertyHint">
+		</constant>
+		<constant name="PROPERTY_HINT_LOCALE_ID" value="43" enum="PropertyHint">
 			Hints that a string property is a locale code. Editing it will show a locale dialog for picking language and country.
 		</constant>
-		<constant name="PROPERTY_HINT_LOCALIZABLE_STRING" value="43" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_LOCALIZABLE_STRING" value="44" enum="PropertyHint">
 			Hints that a dictionary property is string translation map. Dictionary keys are locale codes and, values are translated strings.
 		</constant>
-		<constant name="PROPERTY_HINT_MAX" value="44" enum="PropertyHint">
+		<constant name="PROPERTY_HINT_MAX" value="45" enum="PropertyHint">
 		</constant>
 		<constant name="PROPERTY_USAGE_NONE" value="0" enum="PropertyUsageFlags">
 		</constant>
diff --git a/doc/classes/Image.xml b/doc/classes/Image.xml
index da5b907fab..20e26714bc 100644
--- a/doc/classes/Image.xml
+++ b/doc/classes/Image.xml
@@ -380,6 +380,19 @@
 				[b]Note:[/b] The TinyEXR module is disabled in non-editor builds, which means [method save_exr] will return [constant ERR_UNAVAILABLE] when it is called from an exported project.
 			</description>
 		</method>
+		<method name="save_jpg" qualifiers="const">
+			<return type="int" enum="Error" />
+			<argument index="0" name="path" type="String" />
+			<argument index="1" name="quality" type="float" default="0.75" />
+			<description>
+			</description>
+		</method>
+		<method name="save_jpg_to_buffer" qualifiers="const">
+			<return type="PackedByteArray" />
+			<argument index="0" name="quality" type="float" default="0.75" />
+			<description>
+			</description>
+		</method>
 		<method name="save_png" qualifiers="const">
 			<return type="int" enum="Error" />
 			<argument index="0" name="path" type="String" />
diff --git a/doc/classes/MovieWriter.xml b/doc/classes/MovieWriter.xml
new file mode 100644
index 0000000000..6cc3829b20
--- /dev/null
+++ b/doc/classes/MovieWriter.xml
@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="MovieWriter" inherits="Object" version="4.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
+	<brief_description>
+	</brief_description>
+	<description>
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+		<method name="_get_audio_mix_rate" qualifiers="virtual const">
+			<return type="int" />
+			<description>
+			</description>
+		</method>
+		<method name="_get_audio_speaker_mode" qualifiers="virtual const">
+			<return type="int" enum="AudioServer.SpeakerMode" />
+			<description>
+			</description>
+		</method>
+		<method name="_handles_file" qualifiers="virtual const">
+			<return type="bool" />
+			<argument index="0" name="path" type="String" />
+			<description>
+			</description>
+		</method>
+		<method name="_write_begin" qualifiers="virtual">
+			<return type="int" enum="Error" />
+			<argument index="0" name="movie_size" type="Vector2i" />
+			<argument index="1" name="fps" type="int" />
+			<argument index="2" name="base_path" type="String" />
+			<description>
+			</description>
+		</method>
+		<method name="_write_end" qualifiers="virtual">
+			<return type="void" />
+			<description>
+			</description>
+		</method>
+		<method name="_write_frame" qualifiers="virtual">
+			<return type="int" enum="Error" />
+			<argument index="0" name="frame_image" type="Image" />
+			<argument index="1" name="audio_frame_block" type="const void*" />
+			<description>
+			</description>
+		</method>
+		<method name="add_writer" qualifiers="static">
+			<return type="void" />
+			<argument index="0" name="writer" type="MovieWriter" />
+			<description>
+			</description>
+		</method>
+	</methods>
+</class>
diff --git a/doc/classes/ProjectSettings.xml b/doc/classes/ProjectSettings.xml
index ad95572bf1..281c9adfba 100644
--- a/doc/classes/ProjectSettings.xml
+++ b/doc/classes/ProjectSettings.xml
@@ -547,6 +547,18 @@
 			See [enum DisplayServer.VSyncMode] for possible values and how they affect the behavior of your application.
 			Depending on the platform and used renderer, the engine will fall back to [code]Enabled[/code], if the desired mode is not supported.
 		</member>
+		<member name="editor/movie_writer/disable_vsync" type="bool" setter="" getter="" default="false">
+		</member>
+		<member name="editor/movie_writer/fps" type="int" setter="" getter="" default="60">
+		</member>
+		<member name="editor/movie_writer/mix_rate_hz" type="int" setter="" getter="" default="48000">
+		</member>
+		<member name="editor/movie_writer/mjpeg_quality" type="float" setter="" getter="" default="0.75">
+		</member>
+		<member name="editor/movie_writer/movie_file" type="String" setter="" getter="" default="&quot;&quot;">
+		</member>
+		<member name="editor/movie_writer/speaker_mode" type="int" setter="" getter="" default="0">
+		</member>
 		<member name="editor/node_naming/name_casing" type="int" setter="" getter="" default="0">
 			When creating node names automatically, set the type of casing in this project. This is mostly an editor setting.
 		</member>