avformat/dvdvideodec: reset the subdemuxer on discontinuity instead of flushing

DVDs naturally consist of segmented MPEG-PS blobs within a VOB
(i.e. VOBs are not linear). NAV packs set the segment boundaries.
When switching between segments, discontinuities occur and thus
the subdemuxer needs to be reset. The current approach to manage
this is by invoking ff_read_frame_flush() on the subdemuxer context,
via a callback function which is invoked during the menu or dvdnav
block functions. The same subdemuxer context is used throughout
the demux, with a stretched PTS wrap bits value (64) + disabled
overflow correction, and then flushed on each segment. Eventually,
a play_end context variable is set to declare EOF.

However, this approach causes frame drops. The block read flushes the
demuxer before the frame read is complete, causing frames to drop
on discontinuity. The play_end signal likewise ends playback before
the frame read is complete, causing frames to drop at end of the title.
To compound the issue, the PTS wrap bits value of 64 is wrong;
the VOBU limit is actually 32 and the overflow correction should work.

Instead, EOF the MPEG-PS subdemuxer organically when each VOB segment
ends, and re-open it if needed with the offset after the full frame read
is complete. In doing so, correct the PTS wrap behavior to 32 bits and
remove the play_end/segment_started signals and callback pattern.

Note that the timestamps as reported by the NAV packets are known as
"PTMs", so the fields storing the time prior to adjustment are renamed
accordingly. This makes it more clear when we are offsetting the
NAV packet reported timestamps versus what we present as a demuxer.

Signed-off-by: Marth64 <marth64@proxyid.net>

0 files changed, 0 insertions, 0 deletions