demux: enable thread by default

And change the defaults for the other queue options to reduce latency.

DOCS/man/options.rst

@@ -2046,7 +2046,9 @@ Demuxer
 
 ``--demuxer-thread=<yes|no>``
     Run the demuxer in a separate thread, and let it prefetch a certain amount
-    of packets (default: no).
+    of packets (default: yes). Having this enabled may lead to smoother
+    playback, but on the other hand can add delays to seeking or track
+    switching.
 
 ``--demuxer-readahead-secs=N``
     If ``--demuxer-thread`` is enabled, this controls how much the demuxer

demux/demux.h

@@ -35,11 +35,6 @@
 // and the demuxer pretends EOF was reached.
 #define MAX_PACKS 16000
 #define MAX_PACK_BYTES (400 * 1024 * 1024)
-// Minimum total size of packets queued - the demuxer thread will read more
-// packets, until either number or total size of the packets exceed the minimum.
-// This can actually be configured with command line options.
-#define MIN_PACKS 64
-#define MIN_PACK_BYTES (5 * 1024 * 1024)
 
 enum demuxer_type {
     DEMUXER_TYPE_GENERIC = 0,

options/options.c

@@ -598,9 +598,9 @@ const struct MPOpts mp_default_opts = {
     },
     .stream_cache_pause = 50,
     .stream_cache_unpause = 100,
-    .demuxer_thread = 0,
-    .demuxer_min_packs = MIN_PACKS,
-    .demuxer_min_bytes = MIN_PACK_BYTES,
+    .demuxer_thread = 1,
+    .demuxer_min_packs = 0,
+    .demuxer_min_bytes = 0,
     .demuxer_min_secs = 0.2,
     .network_rtsp_transport = 2,
     .chapterrange = {-1, -1},