Should an explicitly supplied VideoFrameInit.timestamp be preserved exactly across all VideoFrame constructor source types?

[sgsub]

When constructing a WebCodecs VideoFrame from a CanvasImageSource with an explicit integer timestamp, Safari/WebKit deterministically changes some timestamp values by -1 microsecond.

For example:

const canvas = document.createElement('canvas');
canvas.width = 2;
canvas.height = 2;

const frame = new VideoFrame(canvas, {
    timestamp: 1001000
});

console.log(frame.timestamp);

Expected

1001000

Actual in Safari/WebKit

1000999

Reproduced on macOS Safari 26.5.2, iOS 26/18.

[dalecurtis]

That does seem like a bug. This tracker is for spec issues though, so you'll want to file at https://bugs.webkit.org/enter_bug.cgi?product=WebKit&component=Media