stream_Read() can always fail.

fixes 1 byte read overflow

refs #12270

Prior to this patch, if the user specified the --sub-track argument on
the command line, it would not work with MPEG2 streams that contain
EIA-608 closed captions.  It would also cause an abort() on exit.

The crash was because the various functions that select/unselect
streams would check for the p_master member, which isn't set until
after EsOutAdd().  The call to EsOutAdd itself though would call
EsSelect(), which would treat the ES as a regular subtitle stream
and cause a resource leak -- which would cause an abort at exit.

The other change actually makes --sub-track work with the special
case of EIA-608 captions.
Signed-off-by: Rafaël Carré <funman@videolan.org>

This way, when metadata is updated, we only replace the attachments
produced by the demuxer whose metadata changed.

Fixes #11976

Tested by reverting the patch in #11966 (with some fix-ups to pass the
right arguments where the code had changed).
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

When rendering closed captions with VDPAU, nothing frees the subpicture,
causing a leak that bleeds all the memory out of the system within
minutes.
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

This plugin does not access local files.

Otherwise we would loop and write() ts-packet at a time.