The seconds of video a piece of the stream carries: the durations of its samples on the init's video track, in that
track's timescale (mdhd), summed over every moof box in the piece. A sample's duration comes from its trun
record, else the fragment's tfhd default, else the init's trex default. Another track's fragments add nothing,
so an audio-only fragment of a muxed stream reads as 0, and so does a piece without a moof box (an init segment).
null when the init declares no video track with a timescale, or the piece cannot be read: a box whose size runs
past what holds it, a fragment without a readable tfhd, or video samples that no box gives a duration.
The seconds of video a piece of the stream carries: the durations of its samples on the init's video track, in that track's timescale (
mdhd), summed over everymoofbox in the piece. A sample's duration comes from itstrunrecord, else the fragment'stfhddefault, else the init'strexdefault. Another track's fragments add nothing, so an audio-only fragment of a muxed stream reads as 0, and so does a piece without amoofbox (an init segment).nullwhen the init declares no video track with a timescale, or the piece cannot be read: a box whose size runs past what holds it, a fragment without a readabletfhd, or video samples that no box gives a duration.