MP4GetTrackFixedSampleDuration - Get the fixed duration of samples in a
hFile Specifies the mp4 file to which the operation applies.
Specifies the track to which the operation applies.
Upon success, the number of fixed duration of the samples in the track
in track time scale units. Upon an error, MP4_INVALID_DURATION.
MP4GetTrackFixedSampleDuration returns the duration of samples in the
specified track in the mp4 file, if this value is fixed for all
samples. This is typically the case for audio tracks and video tracks.
If the track samples have variable duration, then MP4_INVALID_DURATION