Bug 252989

Created attachment 465196 [details] Reproduction example * Overview: In Safari 16, after appending two segments with a different aspect ratio via MSE and playing the video element, you can see a change of the aspect ratio in the middle of the first segment which does not comply with the expected aspect ratio. This change is also not reflected in the video element's `videoWidth` and `videoHeight`. When we start to play the second segment, we do see a change in the video element's `videoWidth` and `videoHeight` and the element changes to the expected aspect ratio. This is not reproducible if we just append one segment. It's also not reproducible when playing natively (e.g. segments with different aspect ratios in an HLS stream). * Steps to Reproduce: In the attachment, you can find an reproduction page. You can see a change of the aspect ratio around 2-3 seconds and the video element's aspect ratio is set again (but now correct) once we start playing the second segment. When you comment out the second part (appendSecondPart), only the first segment is appended and there is no change of the aspect ratio in the middle of the segment. * Actual Results: Change of the aspect ratio in the middle of the first segment when appending two segments with a different aspect ratio via MSE. * Expected Results: No change of the aspect ratio in the middle of the first segment. * Additional Information: I could not reproduce this issue on Safari 15 (macOS 10, Intel).