Principle:Zai org CogVideo Video Export
Overview
Technique for encoding a sequence of image frames into a playable video file format.
Description
After generating video frames as PIL images, they must be encoded into a standard video container format (MP4) with a specified frame rate. This is the final step in any video generation pipeline, converting in-memory frame data to a persistent, playable file.
The export process involves:
- Frame collection -- Gathering the list of PIL Image frames from the pipeline output
- Video encoding -- Encoding the frames sequentially into an MP4 container using H.264 codec
- Frame rate specification -- Setting the playback speed via frames per second (fps)
- File writing -- Saving the encoded video to disk at the specified output path
Usage
Use as the final step after generating video frames from any CogVideoX pipeline (T2V, I2V, or V2V). Choose fps based on the pipeline variant:
| Pipeline | Recommended FPS | Rationale |
|---|---|---|
| Diffusers pipeline (CogVideoXPipeline) | 16 fps | Default playback rate for diffusers-generated content |
| SAT pipeline | 8 fps | Default playback rate for SAT-generated content |
Theoretical Basis
Video encoding compresses sequential frames using temporal redundancy. MP4 with H.264 codec is the standard output format, providing good compression with wide playback compatibility. Key concepts:
- Frame rate determines playback speed -- CogVideoX generates content intended for 8-16 fps playback
- Container format (MP4) provides the file structure for storing encoded video data
- Codec (H.264) handles the actual compression of pixel data, exploiting both spatial (within-frame) and temporal (between-frame) redundancy
The choice of frame rate directly affects the perceived motion speed. Since CogVideoX models are trained on video data at specific frame rates, using the recommended fps ensures natural-looking playback.