mpegpsdemux uses raw PTS values from the stream, which often start at a non-zero timestamp. To avoid an initial delay, we rebase the PTS by subtracting the first raw value so that the buffer timeline begins at zero for the MPEG-I splitter in DirectShow. Without this adjustment, the first sample would not be presented until its original (non-zero) timestamp in MPEG-1 system stream. Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59565 -- v3: winegstreamer: Rebase PTS values so the stream starts at zero. winegstreamer: Change wg_parser_create argument from bool to bit flags. quartz/tests: Add a timestamp test for the first sample. winegstreamer: Make sure every stream has a buffer or an initial gap on initialization. https://gitlab.winehq.org/wine/wine/-/merge_requests/10864