Videotoolbox: incomplete decoding and massive framedrop for 3840x1080 mp4v
For specifically crafted MPEG-4 Visual (Advanced Simple@L3) content with 3840x1080 dimensions, VT will only decode the first few frames and then drop everything afterwards.
See the RED_8mm_TEST_48fps.mov and RED_8mm_TEST_24fps.mov samples on Quincy (which may NOT be shared publicly).
On iOS, there is also image corruption (see attachment).