demux: drop redundant SEEK_BACKWARD flag

Seems like most code dealing with this was for setting it in redundant
cases. Now SEEK_BACKWARD is redundant, and SEEK_FORWARD is the odd one
out.

Also fix that SEEK_FORWARD was not correctly unset in try_seek_cache().

In demux_mkv_seek(), make the arbitrary decision that a video stream is
not required for the subtitle prefetch logic to be active. We might want
subtitles with long duration even with audio only playback, or if the
file is used as external subtitle.

1 files changed, 2 insertions, 2 deletions

diff --git a/demux/demux.h b/demux/demux.h
index 9c9824658b..64b9f9f561 100644
--- a/demux/demux.h
+++ b/demux/demux.h
@@ -47,7 +47,7 @@ struct demux_ctrl_reader_state {
     double ts_start; // approx. timestamp for the earliest packet buffered
     double ts_min; // timestamp of the earliest packet in backward cache
                    // that can be seeked to (i.e. all streams have such
-                   // a packet for which SEEK_BACKWARD can be executed)
+                   // a packet for which normal seeks can be executed)
     double ts_max; // timestamp of latest packet in forward cache that can be
                    // seeked to
 };
@@ -60,7 +60,7 @@ struct demux_ctrl_stream_ctrl {
 
 #define SEEK_FACTOR   (1 << 1)      // argument is in range [0,1]
 #define SEEK_FORWARD  (1 << 2)      // prefer later time if not exact
-#define SEEK_BACKWARD (1 << 3)      // prefer earlier time if not exact
+                                    // (if unset, prefer earlier time)
 #define SEEK_HR       (1 << 5)      // hr-seek (this is a weak hint only)
 
 // Strictness of the demuxer open format check.