stream_dvd, cache: hack seeking with --cache + dvd:// back into working

This was broken at some unknown point (even before the recent cache
changes). There are several problems:
- stream_dvd returning a random stream position, confusing the cache
  layer (cached data and stream data lost their 1:1 corrospondence by
  position)
- this also confused the mechanism added with commit a9671524, which
  basically triggered random seeking (although this was not the only
  problem)
- demux_lavf requesting seeks in the stream layer, which resulted in
  seeks in the cache or the real stream

Fix this by completely removing byte-based seeking from stream_dvd. This
already works fine for stream_dvdnav and stream_bluray. Now all these
streams do time-based seeks, and pretend to be infinite streams of data,
and the rest of the player simply doesn't care about the stream byte
positions.

demux/demux_lavf.c

@@ -130,6 +130,8 @@ static int64_t mp_seek(void *opaque, int64_t pos, int whence)
     struct demuxer *demuxer = opaque;
     struct stream *stream = demuxer->stream;
     int64_t current_pos;
+    if (stream_manages_timeline(stream))
+        return -1;
     MP_DBG(demuxer, "mp_seek(%p, %"PRId64", %d)\n",
            stream, pos, whence);
     if (whence == SEEK_CUR)

stream/cache.c

@@ -233,7 +233,7 @@ static bool cache_fill(struct priv *s)
         cache_drop_contents(s);
     }
 
-    if (stream_tell(s->stream) != s->max_filepos) {
+    if (stream_tell(s->stream) != s->max_filepos && s->seekable) {
         MP_VERBOSE(s, "Seeking underlying stream: %"PRId64" -> %"PRId64"\n",
                    stream_tell(s->stream), s->max_filepos);
         stream_seek(s->stream, s->max_filepos);

stream/stream_dvd.c

@@ -305,38 +305,6 @@ read_next:
   return d->cur_pack-1;
 }
 
-static void dvd_seek(stream_t *stream, dvd_priv_t *d, int pos)
-{
-  d->packs_left=-1;
-  d->cur_pack=pos;
-
-  // check if we stay in current cell (speedup things, and avoid angle skip)
-  if(d->cur_pack>d->cell_last_pack ||
-     d->cur_pack<d->cur_pgc->cell_playback[ d->cur_cell ].first_sector) {
-
-    // ok, cell change, find the right cell!
-    cell_playback_t *cell;
-    for(d->cur_cell=0; d->cur_cell < d->cur_pgc->nr_of_cells; d->cur_cell++) {
-      cell = &(d->cur_pgc->cell_playback[d->cur_cell]);
-      if(cell->block_type == BLOCK_TYPE_ANGLE_BLOCK && cell->block_mode != BLOCK_MODE_FIRST_CELL)
-        continue;
-      d->cell_last_pack=cell->last_sector;
-      if(d->cur_pack<cell->first_sector) {
-        d->cur_pack=cell->first_sector;
-        break;
-      }
-      if(d->cur_pack<=d->cell_last_pack) break; // ok, we find it! :)
-    }
-  }
-
-  MP_VERBOSE(stream, "DVD Seek! lba=0x%X  cell=%d  packs: 0x%X-0x%X  \n",
-    d->cur_pack,d->cur_cell,d->cur_pgc->cell_playback[ d->cur_cell ].first_sector,d->cell_last_pack);
-
-  // if we're in interleaved multi-angle cell, find the right angle chain!
-  // (read Navi block, and use the seamless angle jump table)
-  d->angle_seek=1;
-}
-
 static int fill_buffer(stream_t *s, char *buf, int len)
 {
   int64_t pos;
@@ -345,16 +313,9 @@ static int fill_buffer(stream_t *s, char *buf, int len)
   pos = dvd_read_sector(s, s->priv, buf);
   if (pos < 0)
     return -1;
-  // dvd_read_sector() sometimes internally skips disk-level blocks
-  s->pos = 2048*(pos - 1);
   return 2048; // full sector
 }
 
-static int seek(stream_t *s, int64_t newpos) {
-  dvd_seek(s, s->priv,newpos/2048);
-  return 1;
-}
-
 static void stream_dvd_close(stream_t *s) {
   dvd_priv_t *d = s->priv;
   ifoClose(d->vts_file);
@@ -976,7 +937,6 @@ static int open_s(stream_t *stream, int mode)
     stream->sector_size = 2048;
     stream->flags = MP_STREAM_SEEK;
     stream->fill_buffer = fill_buffer;
-    stream->seek = seek;
     stream->control = control;
     stream->close = stream_dvd_close;
     stream->start_pos = (int64_t)d->cur_pack*2048;