core: automatically pause on low cache

When the cache fill status goes below a certain threshold, automatically
pause the player. When the cache is filled again, unpause again.

This is intended to help with streaming from http. It's better to pause
a while, rather than exposing extremely crappy behavior when packet
reads during decoding block the entire player.

In theory, we should try to increase the cache if underruns happen too
often. Unfortunately, changing the cache implementation would be very
hard, because it's insane code (forks, uses shared memory and "volatile"
etc.). So for now, this just reduces the frequency of the stuttering if
the network is absolutely too slow to play the stream in realtime.

1 files changed, 8 insertions, 1 deletions

diff --git a/stream/cache2.c b/stream/cache2.c
index 8b35150321..7744f2cba9 100644
--- a/stream/cache2.c
+++ b/stream/cache2.c
@@ -93,6 +93,7 @@ typedef struct {
   volatile int control_res;
   volatile double stream_time_length;
   volatile double stream_time_pos;
+  volatile int idle;
 } cache_vars_t;
 
 static void cache_wakeup(stream_t *s)
@@ -420,6 +421,7 @@ static void cache_mainloop(cache_vars_t *s) {
 #endif
     do {
         if (!cache_fill(s)) {
+            s->idle = 1;
 #if FORKED_CACHE
             // Let signal wake us up, we cannot leave this
             // enabled since we do not handle EINTR in most places.
@@ -436,8 +438,10 @@ static void cache_mainloop(cache_vars_t *s) {
             sa.sa_handler = SIG_IGN;
             sigaction(SIGUSR1, &sa, NULL);
 #endif
-        } else
+        } else {
             sleep_count = 0;
+            s->idle = 0;
+        }
     } while (cache_execute_control(s));
 }
 
@@ -624,6 +628,9 @@ int cache_do_control(stream_t *stream, int cmd, void *arg) {
     case STREAM_CTRL_GET_CACHE_FILL:
       *(int64_t *)arg = s->max_filepos - s->read_filepos;
       return STREAM_OK;
+    case STREAM_CTRL_GET_CACHE_IDLE:
+      *(int *)arg = s->idle;
+      return STREAM_OK;
     case STREAM_CTRL_SEEK_TO_TIME:
       s->control_double_arg = *(double *)arg;
       s->control = cmd;