Video exporting by calling FFMPEG externally (#980)

* Basic mp4 exporting, needs ffmpeg

* Add avi, ogv and mkv file exporting

* Add webm exporting

* Set ffmpeg path in the preferences

* Show an error message if the video fails to export

* Make sure to delete the temp files even if video exporting fails

src/Autoload/Export.gd

@@ -4,10 +4,24 @@ enum ExportTab { IMAGE = 0, SPRITESHEET = 1 }
 enum Orientation { ROWS = 0, COLUMNS = 1 }
 enum AnimationDirection { FORWARD = 0, BACKWARDS = 1, PING_PONG = 2 }
 ## See file_format_string, file_format_description, and ExportDialog.gd
-enum FileFormat { PNG, WEBP, JPEG, GIF, APNG }
+enum FileFormat { PNG, WEBP, JPEG, GIF, APNG, MP4, AVI, OGV, MKV, WEBM }
+
+const TEMP_PATH := "user://tmp"
 
 ## List of animated formats
-var animated_formats := [FileFormat.GIF, FileFormat.APNG]
+var animated_formats := [
+	FileFormat.GIF,
+	FileFormat.APNG,
+	FileFormat.MP4,
+	FileFormat.AVI,
+	FileFormat.OGV,
+	FileFormat.MKV,
+	FileFormat.WEBM
+]
+
+var ffmpeg_formats := [
+	FileFormat.MP4, FileFormat.AVI, FileFormat.OGV, FileFormat.MKV, FileFormat.WEBM
+]
 
 ## A dictionary of custom exporter generators (received from extensions)
 var custom_file_formats := {}
@@ -262,23 +276,28 @@ func export_processed_images(
 			return result
 
 	if is_single_file_format(project):
-		var exporter: AImgIOBaseExporter
-		if project.file_format == FileFormat.APNG:
-			exporter = AImgIOAPNGExporter.new()
+		if is_using_ffmpeg(project.file_format):
+			var video_exported := export_video(export_paths)
+			if not video_exported:
+				return false
 		else:
-			exporter = GIFAnimationExporter.new()
-		var details := {
-			"exporter": exporter,
-			"export_dialog": export_dialog,
-			"export_paths": export_paths,
-			"project": project
-		}
-		if not _multithreading_enabled():
-			export_animated(details)
-		else:
-			if gif_export_thread.is_started():
-				gif_export_thread.wait_to_finish()
-			gif_export_thread.start(export_animated.bind(details))
+			var exporter: AImgIOBaseExporter
+			if project.file_format == FileFormat.APNG:
+				exporter = AImgIOAPNGExporter.new()
+			else:
+				exporter = GIFAnimationExporter.new()
+			var details := {
+				"exporter": exporter,
+				"export_dialog": export_dialog,
+				"export_paths": export_paths,
+				"project": project
+			}
+			if not _multithreading_enabled():
+				export_animated(details)
+			else:
+				if gif_export_thread.is_started():
+					gif_export_thread.wait_to_finish()
+				gif_export_thread.start(export_animated.bind(details))
 	else:
 		var succeeded := true
 		for i in range(processed_images.size()):
@@ -334,6 +353,39 @@ func export_processed_images(
 	return true
 
 
+## Uses FFMPEG to export a video
+func export_video(export_paths: PackedStringArray) -> bool:
+	DirAccess.make_dir_absolute(TEMP_PATH)
+	var temp_path_real := ProjectSettings.globalize_path(TEMP_PATH)
+	var input_file_path := temp_path_real.path_join("input.txt")
+	var input_file := FileAccess.open(input_file_path, FileAccess.WRITE)
+	for i in range(processed_images.size()):
+		var temp_file_name := str(i + 1).pad_zeros(number_of_digits) + ".png"
+		var temp_file_path := temp_path_real.path_join(temp_file_name)
+		processed_images[i].save_png(temp_file_path)
+		input_file.store_line("file '" + temp_file_name + "'")
+		input_file.store_line("duration %s" % durations[i])
+	input_file.close()
+	var ffmpeg_execute: PackedStringArray = [
+		"-y", "-f", "concat", "-i", input_file_path, export_paths[0]
+	]
+	var output := []
+	var success := OS.execute(Global.ffmpeg_path, ffmpeg_execute, output, true)
+	print(output)
+	var temp_dir := DirAccess.open(TEMP_PATH)
+	for file in temp_dir.get_files():
+		temp_dir.remove(file)
+	DirAccess.remove_absolute(TEMP_PATH)
+	if success < 0 or success > 1:
+		var fail_text := """Video failed to export. Make sure you have FFMPEG installed
+			and have set the correct path in the preferences."""
+		Global.error_dialog.set_text(tr(fail_text))
+		Global.error_dialog.popup_centered()
+		Global.dialog_open(true)
+		return false
+	return true
+
+
 func export_animated(args: Dictionary) -> void:
 	var project: Project = args["project"]
 	var exporter: AImgIOBaseExporter = args["exporter"]
@@ -397,6 +449,16 @@ func file_format_string(format_enum: int) -> String:
 			return ".gif"
 		FileFormat.APNG:
 			return ".apng"
+		FileFormat.MP4:
+			return ".mp4"
+		FileFormat.AVI:
+			return ".avi"
+		FileFormat.OGV:
+			return ".ogv"
+		FileFormat.MKV:
+			return ".mkv"
+		FileFormat.WEBM:
+			return ".webm"
 		_:
 			# If a file format description is not found, try generating one
 			if custom_exporter_generators.has(format_enum):
@@ -418,6 +480,16 @@ func file_format_description(format_enum: int) -> String:
 			return "GIF Image"
 		FileFormat.APNG:
 			return "APNG Image"
+		FileFormat.MP4:
+			return "MPEG-4 Video"
+		FileFormat.AVI:
+			return "AVI Video"
+		FileFormat.OGV:
+			return "OGV Video"
+		FileFormat.MKV:
+			return "Matroska Video"
+		FileFormat.WEBM:
+			return "WebM Video"
 		_:
 			# If a file format description is not found, try generating one
 			for key in custom_file_formats.keys():
@@ -426,12 +498,25 @@ func file_format_description(format_enum: int) -> String:
 			return ""
 
 
-## True when exporting to .gif and .apng (and potentially video formats in the future)
-## False when exporting to .png, and other non-animated formats in the future
+## True when exporting to .gif, .apng and video
+## False when exporting to .png, .jpg and static .webp
 func is_single_file_format(project := Global.current_project) -> bool:
 	return animated_formats.has(project.file_format)
 
 
+func is_using_ffmpeg(format: FileFormat) -> bool:
+	return ffmpeg_formats.has(format)
+
+
+func is_ffmpeg_installed() -> bool:
+	if Global.ffmpeg_path.is_empty():
+		return false
+	var ffmpeg_executed := OS.execute(Global.ffmpeg_path, [])
+	if ffmpeg_executed == 0 or ffmpeg_executed == 1:
+		return true
+	return false
+
+
 func _create_export_path(multifile: bool, project: Project, frame := 0) -> String:
 	var path := project.file_name
 	# Only append frame number when there are multiple files exported

src/Autoload/Global.gd

@@ -131,6 +131,8 @@ var show_y_symmetry_axis := false
 var open_last_project := false
 ## Found in Preferences. If [code]true[/code], asks for permission to quit on exit.
 var quit_confirmation := false
+## Found in Preferences. Refers to the ffmpeg location path.
+var ffmpeg_path := ""
 ## Found in Preferences. If [code]true[/code], the zoom is smooth.
 var smooth_zoom := true
 ## Found in Preferences. If [code]true[/code], the zoom is restricted to integral multiples of 100%.

src/Preferences/PreferencesDialog.gd

@@ -7,6 +7,7 @@ var preferences: Array[Preference] = [
 	Preference.new(
 		"quit_confirmation", "Startup/StartupContainer/QuitConfirmation", "button_pressed"
 	),
+	Preference.new("ffmpeg_path", "Startup/StartupContainer/FFMPEGPath", "text"),
 	Preference.new("shrink", "%ShrinkSlider", "value"),
 	Preference.new("font_size", "Interface/InterfaceOptions/FontSizeSlider", "value"),
 	Preference.new("dim_on_popup", "Interface/InterfaceOptions/DimCheckBox", "button_pressed"),
@@ -202,6 +203,10 @@ func _ready() -> void:
 				node.item_selected.connect(
 					_on_Preference_value_changed.bind(pref, restore_default_button)
 				)
+			"text":
+				node.text_changed.connect(
+					_on_Preference_value_changed.bind(pref, restore_default_button)
+				)
 
 		var global_value = Global.get(pref.prop_name)
 		if Global.config_cache.has_section_key("preferences", pref.prop_name):

src/Preferences/PreferencesDialog.tscn

@@ -92,6 +92,13 @@ layout_mode = 2
 mouse_default_cursor_shape = 2
 text = "On"
 
+[node name="FFMPEGPathLabel" type="Label" parent="HSplitContainer/VBoxContainer/ScrollContainer/RightSide/Startup/StartupContainer"]
+layout_mode = 2
+text = "FFMPEG path"
+
+[node name="FFMPEGPath" type="LineEdit" parent="HSplitContainer/VBoxContainer/ScrollContainer/RightSide/Startup/StartupContainer"]
+layout_mode = 2
+
 [node name="Language" type="VBoxContainer" parent="HSplitContainer/VBoxContainer/ScrollContainer/RightSide"]
 visible = false
 layout_mode = 2

src/UI/Dialogs/ExportDialog.gd

@@ -13,7 +13,12 @@ var image_exports: Array[Export.FileFormat] = [
 	Export.FileFormat.WEBP,
 	Export.FileFormat.JPEG,
 	Export.FileFormat.GIF,
-	Export.FileFormat.APNG
+	Export.FileFormat.APNG,
+	Export.FileFormat.MP4,
+	Export.FileFormat.AVI,
+	Export.FileFormat.OGV,
+	Export.FileFormat.MKV,
+	Export.FileFormat.WEBM,
 ]
 var spritesheet_exports: Array[Export.FileFormat] = [
 	Export.FileFormat.PNG, Export.FileFormat.WEBP, Export.FileFormat.JPEG
@@ -188,6 +193,12 @@ func set_file_format_selector() -> void:
 	match Export.current_tab:
 		Export.ExportTab.IMAGE:
 			_set_file_format_selector_suitable_file_formats(image_exports)
+			if Export.is_ffmpeg_installed():
+				for format in Export.ffmpeg_formats:
+					file_format_options.set_item_disabled(format, false)
+			else:
+				for format in Export.ffmpeg_formats:
+					file_format_options.set_item_disabled(format, true)
 		Export.ExportTab.SPRITESHEET:
 			_set_file_format_selector_suitable_file_formats(spritesheet_exports)
 
@@ -246,9 +257,9 @@ func update_dimensions_label() -> void:
 
 func open_path_validation_alert_popup(path_or_name: int = -1) -> void:
 	# 0 is invalid path, 1 is invalid name
-	var error_text := "DirAccess path and file name are not valid!"
+	var error_text := "Directory path and file name are not valid!"
 	if path_or_name == 0:
-		error_text = "DirAccess path is not valid!"
+		error_text = "Directory path is not valid!"
 	elif path_or_name == 1:
 		error_text = "File name is not valid!"