core: add demux_sub pseudo demuxer

Subtitle files are opened in mplayer.c, not using the demuxer
infrastructure in general. Pretend that this is not the case (outside of
the loading code) by opening a pseudo demuxer that does nothing. One
advantage is that the initialization code is now the same, and there's
no confusion about what the difference between track->stream,
track->sh_sub and mpctx->sh_sub is supposed to be.

This is a bit stupid, and it would be much better if there were proper
subtitle demuxers (there are many in recent FFmpeg, but not Libav). So
for now this is just a transition to a more proper architecture. Look
at demux_sub like an artifical limb: it's ugly, but don't hate it - it
helps you to get on with your life.

1 files changed, 3 insertions, 6 deletions

diff --git a/core/mp_core.h b/core/mp_core.h
index db6bc570e1..d7aa42e38d 100644
--- a/core/mp_core.h
+++ b/core/mp_core.h
@@ -103,12 +103,9 @@ struct track {
     // Invariant: (!demuxer && !stream) || stream->demuxer == demuxer
     struct sh_stream *stream;
 
-    // NOTE: demuxer subtitles, i.e. if stream!=NULL, do not use the following
-    //       fields. The data is stored in stream->sub this case.
-
-    // External text subtitle using libass subtitle renderer.
-    // The sh_sub is a dummy and doesn't belong to a demuxer.
-    struct sh_sub *sh_sub;
+    // For external subtitles, which are read fully on init. Do not attempt
+    // to read packets from them.
+    bool preloaded;
 };
 
 enum {