Incorrect rendering h265/HEVC video with alpha channel

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build Process
• Unit Testing
• Internalization
• Friendly Errors
• Other (specify if possible)

p5.js version

1.6.0

Web browser and version

111.0.5563.64 (Official Build) (arm64)

Operating System

macOS Ventura 13.2.1

Steps to reproduce this

When using image() to render a video with an alpha channel, pixels from the previous frames are not being cleared.

Steps:

1. Export a video with alpha channel using h265 codec (macOS can convert to by right click > encode selected video files)
2. Load it in a p5.js script with createVideo()
3. Display it with image()
4. Observe frames not clearing.

Snippet:

• Example of bug when rendering inside canvas: https://editor.p5js.org/araid/sketches/TcKkF4gOb
• The video renders correctly outside canvas (not using image()): https://editor.p5js.org/araid/sketches/7beM-GM1k

Start by reproducing the issue with the linked p5.js Editor sketches, using createVideo() to load an H.265/HEVC video with an alpha channel and image() to draw it. Compare the canvas rendering with playback outside the canvas, then trace the video-image rendering path; done means successive frames clear correctly without pixels from prior frames.