Creates a sub-buffer from parent at offset and size. This sub-buffer uses the actual memory space of the parent buffer. This function will copy the offset and timestamp fields when the offset is 0. If not, they will be set to GST_CLOCK_TIME_NONE and GST_BUFFER_OFFSET_NONE
the offset into parent gstreamer.Buffer at which the new sub-buffer begins.
the size of the new gstreamer.Buffer sub-buffer, in bytes. If -1, all data is copied.