demux_disc: bluray: potentially fix some aspects of seeking

When flushing the AVIOContext, make sure it can't seek back to discarded
data. buf_ptr is just the current read position, while buf_end - buffer
is the actual buffer size. Since mpegts.c is littered with seek calls,
it might be that the ability to seek could read

Mark the stream (which the demuxer uses) as not seekable. The cache can
enable seeking again (this behavior is sometimes useful for other
things). I think this should have had no bad influence in theory, since
seeking BD/DVD first does the "real" seek, then flushes libavformat and
reads new packets.

2 files changed, 7 insertions, 1 deletions

diff --git a/demux/demux_disc.c b/demux/demux_disc.c
index 5175f89e01..f0ddc1e827 100644
--- a/demux/demux_disc.c
+++ b/demux/demux_disc.c
@@ -310,6 +310,12 @@ static int d_open(demuxer_t *demuxer, enum demux_check check)
     // Can be seekable even if the stream isn't.
     demuxer->seekable = true;
 
+    // With cache enabled, the stream can be seekable. This causes demux_lavf.c
+    // (actually libavformat/mpegts.c) to seek sometimes when reading a packet.
+    // It does this to seek back a bit in case the current file position points
+    // into the middle of a packet.
+    demuxer->stream->seekable = false;
+
     add_dvd_streams(demuxer);
     add_streams(demuxer);
     add_stream_chapters(demuxer);
diff --git a/demux/demux_lavf.c b/demux/demux_lavf.c
index 578e061d46..8dd248aec1 100644
--- a/demux/demux_lavf.c
+++ b/demux/demux_lavf.c
@@ -1014,7 +1014,7 @@ redo:
                       AVSEEK_FLAG_BYTE);
         // avio_flush() is designed for write-only streams, and does the wrong
         // thing when reading. Flush it manually instead.
-        priv->avfc->pb->buf_ptr = priv->avfc->pb->buf_end;
+        priv->avfc->pb->buf_ptr = priv->avfc->pb->buf_end = priv->avfc->pb->buffer;
         stream_drop_buffers(demuxer->stream);
         return DEMUXER_CTRL_OK;
     default: