Fix short term reference picture list parsing. Before this change, `deltaPocS0`
was derived by adding one to the value of the syntax element
`delta_poc_s0_minus1`, but (maybe surprising) the specification actually says
that `DeltaPocS0[stRpsIdx][i]` should be assigned the negation
`-(delta_poc_s0_minus1[i] + 1)` on the first iteration, then that value added
to the previous value on previous iterations. See equations (7-67) to (7-70) in
the 2021-08 version of the H.265/HEVC specification.
Also read the number of long term reference pictures once rather than on every
loop iteration (subsection 7.3.2.2.1).
PiperOrigin-RevId: 551852999
MP4 edit lists sometimes ask to start playback between two samples.
If this happens, we currently change the timestamp of the first
sample to zero to trim it (e.g. to display the first frame for a
slightly shorter period of time). However, we can't do this to audio
samples are they have an inherent duration and trimming them this
way is not possible.
#minor-release
PiperOrigin-RevId: 543420218
