What It Does
MP4 + Alpha Converter addresses a specific problem: After Effects doesn’t natively support rendering transparent video to MP4 format. This script solves that by splitting each footage item into two MP4 files (one RGB, one alpha channel) and automatically merging them back into a composition that replaces the original footage throughout your project. The result is dramatically smaller file sizes without losing transparency.
The script works with both video files and image sequences. If you’re working with cloud storage, archived projects, or storage-intensive jobs, it can reduce gigabytes of footage to megabytes while maintaining the same visual appearance in your comps.
Key Features
One-click conversion. Select your footage items in the project panel, click Convert, and the script handles the rest. It splits each item into RGB and alpha channels, renders both to MP4, creates a composition that combines them, and replaces all instances of the original footage across your project.
Audio preservation. If your footage has an audio track, it gets preserved in the RGB channel so your comps maintain the same sound behavior.
Automatic file management. The script renames duplicate filenames by adding a counter and fixes invalid file system characters. You can set a custom output folder or let it default to your project directory. The “Organize” button moves converted files into proper subfolders to keep your project clean.
Vertical line artifact fix. MP4/MPEG format has a known limitation with resolutions that aren’t multiples of 8, which creates a vertical line artifact. The script automatically corrects this without changing how the footage looks.
Render queue integration. Convert and render immediately, or add items to the render queue for batch processing later.
Who It’s For
This is useful for motion designers managing archived projects or productions with heavy cloud traffic. If you’re working with transparent overlays, lower thirds, or animated elements that need to be stored efficiently, this converts your high-quality source files to web-friendly MP4 while keeping the alpha channel functional.
The script works best with standard 8-bpc footage (your typical MOV, PNG sequences, etc.). It’s not designed for HDR or EXR sequences, which get converted down to 8-bpc. If you’re doing intense color grading later, stick with lossless formats. MP4/h264 compression degrades chrominance information in ways that become visible under heavy color correction.
Limitations
The script only processes video and image sequence items, not solids or other layer types. Maximum resolution and frame rate are limited to h.264 standard specifications. Items with frame rates below 1 FPS won’t convert correctly.
For After Effects versions before 2023, you need the AfterCodecs plugin installed to render MP4 (not included). AE 2023 and later have native MP4 rendering built in.
Pricing
$29.99 for a single-user license. Upgrade pricing is available for previous buyers, but you need to log in to see your eligibility.