A piece of fragmented MP4 as a frame: Piece from its first box; for an init segment, Width and Height from its
video track; for a fragment, PresentationTimeMs and KeyFrame from its first video sample, timed by init's video
track. A fragment without a video sample (an audio-only fragment of a muxed stream), one before any init, or one that
can't be read gets neither: it still plays.
The MIME type stays as the provider sent it when it names video/mp4; otherwise it is 'video/mp4'. Bytes labelled
video/mp4 that open with no MP4 box (a lone mdat) are a fragment.
A piece of fragmented MP4 as a frame:
Piecefrom its first box; for an init segment,WidthandHeightfrom its video track; for a fragment,PresentationTimeMsandKeyFramefrom its first video sample, timed byinit's video track. A fragment without a video sample (an audio-only fragment of a muxed stream), one before any init, or one that can't be read gets neither: it still plays.The MIME type stays as the provider sent it when it names
video/mp4; otherwise it is'video/mp4'. Bytes labelledvideo/mp4that open with no MP4 box (a lonemdat) are a fragment.