playlist: temporize on errors

When repeat/loop is enabled, and items fail to play, VLC enters an
infinite liveloop and floods errors.

We cannot just stop on errors, because retrying indefinitely may be the
expected behavior:
<https://trac.videolan.org/vlc/ticket/18582#comment:3>

Instead, wait some delay before starting the next item, depending on the
number of consecutive errors:
 - 1st error: 100ms
 - 2nd error: 200ms
 - 3rd error: 400ms
 - 4th error: 800ms
 - 5th error: 1.6s
 - further errors: 3.2s

A single successful playback resets the errors counter.

Note-from-committer:
--------------------
This is not a complete and correct fix, but this hides the issue for
our users for the vast majority of the cases.
Once a proper fix is done, please revert this.

Ref #5901

Fixes #6245 #6339 #7305 #7798 #8893 #9230 #11066 #11961 #12104
      #12909 #13878 #14679 #15805 #16697 #17660 #18582 #18942 #19284
      #19313 #20365 #21564 #21672 #21897 #22118

src/input/input.c

@@ -3217,6 +3217,8 @@ static void input_ChangeState( input_thread_t *p_input, int i_state )
     input_priv(p_input)->i_state = i_state;
     if( i_state == ERROR_S )
         input_item_SetErrorWhenReading( input_priv(p_input)->p_item, true );
+    else if ( i_state == PLAYING_S )
+        input_item_SetErrorWhenReading( input_priv(p_input)->p_item, false );
     input_SendEventState( p_input, i_state );
 }
 

src/playlist/engine.c

@@ -261,6 +261,7 @@ playlist_t *playlist_Create( vlc_object_t *p_parent )
     pl_priv(p_playlist)->status.p_item = NULL;
     pl_priv(p_playlist)->status.p_node = p_playlist->p_playing;
     pl_priv(p_playlist)->request.b_request = false;
+    pl_priv(p_playlist)->i_consecutive_errors = 0;
     p->request.input_dead = false;
 
     if (ml != NULL)

src/playlist/playlist_internal.h

@@ -87,6 +87,7 @@ typedef struct playlist_private_t
 
     int      i_last_playlist_id; /**< Last id to an item */
     bool     b_reset_currently_playing; /** Reset current item array */
+    unsigned i_consecutive_errors; /**< Number of consecutive items in error */
 
     bool     b_tree; /**< Display as a tree */
     bool     b_preparse; /**< Preparse items */

src/playlist/thread.c

@@ -421,7 +421,7 @@ static playlist_item_t *NextItem( playlist_t *p_playlist )
     return p_new;
 }
 
-static void LoopInput( playlist_t *p_playlist )
+static bool LoopInput( playlist_t *p_playlist )
 {
     playlist_private_t *p_sys = pl_priv(p_playlist);
     input_thread_t *p_input = p_sys->p_input;
@@ -439,6 +439,10 @@ static void LoopInput( playlist_t *p_playlist )
         vlc_cond_wait( &p_sys->signal, &p_sys->lock );
     }
 
+    input_item_t *item = input_GetItem(p_input);
+    assert(item);
+    bool ok = !input_item_HasErrorWhenReading(item);
+
     /* This input is dead. Remove it ! */
     PL_DEBUG( "dead input" );
     p_sys->p_input = NULL;
@@ -455,6 +459,8 @@ static void LoopInput( playlist_t *p_playlist )
 
     input_Close( p_input );
     PL_LOCK;
+
+    return ok;
 }
 
 static bool Next( playlist_t *p_playlist )
@@ -492,7 +498,19 @@ static void *Thread ( void *data )
         /* Playlist in running state */
         while( !p_sys->killed && Next( p_playlist ) )
         {
-            LoopInput( p_playlist );
+            bool ok = LoopInput( p_playlist );
+            if (ok)
+                p_sys->i_consecutive_errors = 0;
+            else
+            {
+                if (p_sys->i_consecutive_errors < 6)
+                    p_sys->i_consecutive_errors++;
+
+                int slowdown = 1 << p_sys->i_consecutive_errors;
+                /* 100ms, 200ms, 400ms, 800ms, 1.6s, 3.2s */
+                mtime_t deadline = mdate() + slowdown * 100000L; /* usecs */
+                vlc_cond_timedwait(&p_sys->signal, &p_sys->lock, deadline);
+            }
             played = true;
         }