muvid.choreo.render

Draw a ChoreoScene frame by frame and encode it.

numpy paints each frame — filled circles, rects, triangles, lines, diamonds and rings, from coordinate grids and coverage masks with a one-pixel anti-aliased edge — and the raw rgb24 frames are piped straight into ffmpeg’s stdin, which muxes the song and encodes the YouTube-spec H.264/AAC mp4 muvid.visualize.video produces. Nothing touches the disk between the scene and the mp4: a 3-minute 720p render is ~15 GB of frames, and that is why this is a pipe and not a frame directory.

Two things keep it fast enough on a CPU:

• only the dirty pixels are touched — every primitive computes its bounding box and paints inside it; a frame’s cost is the sum of the objects alive in it, not the canvas size;

• the frame buffer is the backdrop copied, so a frame with nothing alive costs one memcpy.

This is the ONE place choreo spawns ffmpeg itself rather than through muvid.visualize.ffmpeg.run_ffmpeg(), because that helper has no stdin seam. It uses the same binary check, the same timeout env var and the same encode/container arguments, so the mp4 it writes is the one verify_video expects; when a streaming primitive lands in muvid.visualize.ffmpeg this should collapse onto it.

Functions

render_scene(scene, *, audio, output, workdir)	Paint every frame of scene, pipe them into ffmpeg, mux audio.
iter_frames(scene)	Every frame of scene, in order.

Classes

RenderedVideo(*, output, duration_s, ...)	What render_scene() produced, and how long it took.
Painter(scene)	Paints frames of one scene.

class muvid.choreo.render.Painter(scene)

Bases: object

Paints frames of one scene. Holds the grids and backdrops between frames.

alive(t)

Objects alive at t. Frames must be asked for in increasing t.

Return type:

list[Obj]

frame(k)

Frame k (at k / fps seconds) as a fresh uint8 HxWx3 array.

Return type:

ndarray

class muvid.choreo.render.RenderedVideo(*, output, duration_s, n_frames, render_s)

Bases: object

What render_scene() produced, and how long it took.

muvid.choreo.render.iter_frames(scene)

Every frame of scene, in order.

Return type:

Iterator[ndarray]

muvid.choreo.render.render_scene(scene, *, audio, output, workdir, crf=18, preset='medium')

Paint every frame of scene, pipe them into ffmpeg, mux audio.

Raises:

• FfmpegError – ffmpeg exited non-zero, died mid-stream, or overran $MUVID_FFMPEG_TIMEOUT_S; the message carries the log’s tail.

• ValueError – the canvas has an odd dimension (yuv420p cannot encode one).

Return type:

RenderedVideo