Pixie Compositor

The Pixie Compositor (/pixie_compositor) is GenMedia Creative Studio’s post-production editing suite. It allows creators to take video clips generated in Veo and audio tracks generated in Lyria, Gemini TTS, or Chirp 3 HD and assemble them into finished multi-shot sequences with transitions, layered soundtracks, and animated GIF exports.

Source Architecture

Layer	File Path	Responsibility
Mesop Page & State	pages/pixie_compositor.py (PixieCompositorState)	Two-tab workspace (Video + Video Concatenation and Video + Audio Layering), Firestore Library media pickers, transition selector, and GIF converter.
Video Processing Engine	models/video_processing.py (process_and_concatenate_videos, layer_audio_on_video, convert_mp4_to_gif)	MoviePy pipeline executing clip concatenation, crossfade/wipe transitions, audio track muxing, and GCS persistence.

Core Editing Workflows

Tab 1: Multi-Video Concatenation & Transitions (process_and_concatenate_videos)

1. Clip Selection: Select 2 or more video clips from the Studio Library (queried from Firestore genmedia_library where mime_type == "video/mp4").
2. Transition Effect Selection (selected_transition):
   • Concatenate (concat): Hard cut sequence (concatenate_videoclips(clips, method="compose")).
   • Crossfade (crossfade): Applies a 1.0s crossfadein overlap between consecutive clips.
   • Wipe (wipe): Applies a directional slide transition (CompositeVideoClip with horizontal position animation) between clips.
3. Render & Persist: MoviePy exports the stitched master clip (libx264, aac, 24 fps), uploads it to gs://<GENMEDIA_BUCKET>/concatenated_videos/, and logs a new MediaItem (media_type="pixie_compositor").

Tab 2: Video + Audio Track Layering (layer_audio_on_video)

1. Asset Selection: Pick a target Video Clip (video_to_layer_uri) and an Audio Track (audio_to_layer_uri, such as a 30-second Lyria score or a Gemini TTS voiceover) from the Studio Library.
2. Audio Muxing: layer_audio_on_video() loads both assets into MoviePy (VideoFileClip and AudioFileClip), trims the audio to match the video duration if the audio track is longer (audio_clip.subclip(0, video_clip.duration)), binds the audio via video_clip.set_audio(audio_clip), and writes the combined MP4 to Cloud Storage.

One-Click MP4-to-GIF Export (convert_mp4_to_gif)

• Both tabs include a Convert to GIF button on the rendered output video that invokes convert_mp4_to_gif() (10 fps) and saves the resulting .gif to Cloud Storage for easy embedding in presentations or chat spaces.