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MovieWriter

Inherits: Object

Abstract class for non-real-time video recording encoders.

Description

Redot can record videos with non-real-time simulation. Like the --fixed-fps command line argument, this forces the reported delta in Node._process functions to be identical across frames, regardless of how long it actually took to render the frame. This can be used to record high-quality videos with perfect frame pacing regardless of your hardware's capabilities.

Redot has 2 built-in MovieWriters:

  • AVI container with MJPEG for video and uncompressed audio (.avi file extension). Lossy compression, medium file sizes, fast encoding. The lossy compression quality can be adjusted by changing ProjectSettings.editor/movie_writer/mjpeg_quality. The resulting file can be viewed in most video players, but it must be converted to another format for viewing on the web or by Redot with VideoStreamPlayer. MJPEG does not support transparency. AVI output is currently limited to a file of 4 GB in size at most.

  • PNG image sequence for video and WAV for audio (.png file extension). Lossless compression, large file sizes, slow encoding. Designed to be encoded to a video file with another tool such as FFmpeg after recording. Transparency is currently not supported, even if the root viewport is set to be transparent.

If you need to encode to a different format or pipe a stream through third-party software, you can extend the MovieWriter class to create your own movie writers. This should typically be done using GDExtension for performance reasons.

Editor usage: A default movie file path can be specified in ProjectSettings.editor/movie_writer/movie_file. Alternatively, for running single scenes, a movie_file metadata can be added to the root node, specifying the path to a movie file that will be used when recording that scene. Once a path is set, click the video reel icon in the top-right corner of the editor to enable Movie Maker mode, then run any scene as usual. The engine will start recording as soon as the splash screen is finished, and it will only stop recording when the engine quits. Click the video reel icon again to disable Movie Maker mode. Note that toggling Movie Maker mode does not affect project instances that are already running.

Note: MovieWriter is available for use in both the editor and exported projects, but it is not designed for use by end users to record videos while playing. Players wishing to record gameplay videos should install tools such as OBS Studio or SimpleScreenRecorder instead.

Methods

int

_get_audio_mix_rate() virtual const

SpeakerMode

_get_audio_speaker_mode() virtual const

bool

_handles_file(path: String) virtual const

Error

_write_begin(movie_size: Vector2i, fps: int, base_path: String) virtual

void

_write_end() virtual

Error

_write_frame(frame_image: Image, audio_frame_block: const void*) virtual

void

add_writer(writer: MovieWriter) static

Method Descriptions

int _get_audio_mix_rate() virtual const 🔗

Called when the audio sample rate used for recording the audio is requested by the engine. The value returned must be specified in Hz. Defaults to 48000 Hz if _get_audio_mix_rate is not overridden.

SpeakerMode _get_audio_speaker_mode() virtual const 🔗

Called when the audio speaker mode used for recording the audio is requested by the engine. This can affect the number of output channels in the resulting audio file/stream. Defaults to AudioServer.SPEAKER_MODE_STEREO if _get_audio_speaker_mode is not overridden.

bool _handles_file(path: String) virtual const 🔗

Called when the engine determines whether this MovieWriter is able to handle the file at path. Must return true if this MovieWriter is able to handle the given file path, false otherwise. Typically, _handles_file is overridden as follows to allow the user to record a file at any path with a given file extension:

func _handles_file(path):
    # Allows specifying an output file with a `.mkv` file extension (case-insensitive),
    # either in the Project Settings or with the `--write-movie <path>` command line argument.
    return path.get_extension().to_lower() == "mkv"

Error _write_begin(movie_size: Vector2i, fps: int, base_path: String) virtual 🔗

Called once before the engine starts writing video and audio data. movie_size is the width and height of the video to save. fps is the number of frames per second specified in the project settings or using the --fixed-fps <fps> command line argument.

void _write_end() virtual 🔗

Called when the engine finishes writing. This occurs when the engine quits by pressing the window manager's close button, or when SceneTree.quit is called.

Note: Pressing Ctrl + C on the terminal running the editor/project does not result in _write_end being called.

Error _write_frame(frame_image: Image, audio_frame_block: const void*) virtual 🔗

Called at the end of every rendered frame. The frame_image and audio_frame_block function arguments should be written to.

void add_writer(writer: MovieWriter) static 🔗

Adds a writer to be usable by the engine. The supported file extensions can be set by overriding _handles_file.

Note: add_writer must be called early enough in the engine initialization to work, as movie writing is designed to start at the same time as the rest of the engine.