copySampleValue_
Copies a sample value to the result buffer.
Override this when samples are not stored as flat runs of valueSize values. For example, a glTF CUBICSPLINE track stores an in-tangent, a value and an out-tangent per keyframe, so its sample starts at index * valueSize * 3 + valueSize.
Return
The result buffer.
Parameters
index
An index into the sample value buffer.