If cache was enabled, using ordered chapters could easily crash. The
reason is that enable_cache() reopens the demuxer and closes the old
one. The code after that (reading m->ordered_chapters etc.) then
accessed freed data.
This commit also avoids enabling cache for files which are not used
(which would make opening much slower).
When adding or removing frames to avoid 1-frame seeks on chapter
boundaries, the end of the chapter needs to be pushed or pulled by the
same amount to keep the intended end frame the same.
Since ordered editions can reference external files, when an ordered
chapter references another ordered edition, we have to go and figure out
what is is referencing as well.
When playing a Matroska file with ordered chapters, it may reference
another file by edition uid. When this edition is also ordered, it may
reference other files. When this occurs, the new segment/edition pair is
added to the list of sources to search for.
To support edition references in matroska chapters, editions need to be
remembered for each chapter and source. To facilitate easier management
of these now-paired uids, a single structure is used.
There is uninitialized memory access if the actual size isn't passed
along. In the worst case, this can cause a source to be loaded against
the uninitialized memory, causing a false count of found versus required
sources, preventing the "Failed to find ordered chapter part" message.
Modeled after the old playlist_parser.c, but actually new code, and it
works a bit differently.
Demuxers (and sometimes streams) are the component that should be used
to open files and to determine the file format. This was already done
for subtitles, but playlists still use a separate code path.
core is used in many unix systems for core dumps. For that reason some tools
work under the assumption that the file is indeed a core dump (for example
autoconf does this).
This commit just renames the files. The following one will change all the
includes to fix compilation. This is done this way because git has a easier
time tracing file changes if there is a pure rename commit.
