playlist: go back to nearest well-known playback rate on +/-

Until now, if the rate was not one of the hard-coded value, and the hot
keys would jump not to the nearest known rate, but the second nearest.

Unfortunately, we still have to account for rounding errors in the
input thread, so this is not perfect.

src/playlist/engine.c

@@ -74,10 +74,10 @@ static int RateCallback( vlc_object_t *p_this, char const *psz_cmd,
     return VLC_SUCCESS;
 }
 
-static int RateOffsetCallback( vlc_object_t *p_this, char const *psz_cmd,
+static int RateOffsetCallback( vlc_object_t *obj, char const *psz_cmd,
                                vlc_value_t oldval, vlc_value_t newval, void *p_data )
 {
-    playlist_t *p_playlist = (playlist_t*)p_this;
+    playlist_t *p_playlist = (playlist_t *)obj;
     VLC_UNUSED(oldval); VLC_UNUSED(p_data); VLC_UNUSED(newval);
 
     static const float pf_rate[] = {
@@ -85,48 +85,40 @@ static int RateOffsetCallback( vlc_object_t *p_this, char const *psz_cmd,
         1.0/1,
         3.0/2, 2.0/1, 3.0/1, 4.0/1, 8.0/1, 16.0/1, 32.0/1, 64.0/1,
     };
-    const unsigned i_rate_count = sizeof(pf_rate)/sizeof(*pf_rate);
+    const size_t i_rate_count = sizeof(pf_rate)/sizeof(*pf_rate);
+
+    float f_rate;
+    struct input_thread_t *input;
 
     PL_LOCK;
-    float f_rate = 1.;
-    if( pl_priv( p_playlist )->p_input )
-    {
-       f_rate = var_GetFloat( pl_priv(p_playlist)->p_input, "rate" );
-    }
-    else
-    {
-       f_rate = var_GetFloat( p_playlist, "rate" );
-    }
+    input = pl_priv( p_playlist )->p_input;
+    f_rate = var_GetFloat( input ? (vlc_object_t *)input : obj, "rate" );
     PL_UNLOCK;
 
-    /* Determine the factor closest to the current rate */
-    float f_error;
-    int i_idx;
-    for( unsigned i = 0; i < i_rate_count; i++ )
+    if( !strcmp( psz_cmd, "rate-faster" ) )
     {
-        const float f_test_e = fabs( fabs( f_rate ) - pf_rate[i] );
-        if( i == 0 || f_test_e < f_error )
-        {
-            i_idx = i;
-            f_error = f_test_e;
-        }
+        /* compensate for input rounding errors */
+        float r = f_rate * 1.1;
+        for( size_t i = 0; i < i_rate_count; i++ )
+            if( r < pf_rate[i] )
+            {
+                f_rate = pf_rate[i];
+                break;
+            }
     }
-    assert( i_idx < (int)i_rate_count );
-
-    /* */
-    i_idx += strcmp( psz_cmd, "rate-faster" ) == 0 ? 1 : -1;
-    if( i_idx >= 0 && i_idx < (int)i_rate_count )
+    else
     {
-        const float f_rate_min = (float)INPUT_RATE_DEFAULT / INPUT_RATE_MAX;
-        const float f_rate_max = (float)INPUT_RATE_DEFAULT / INPUT_RATE_MIN;
-        const float f_sign = f_rate >= 0 ? +1. : -1.;
-
-        var_SetFloat( p_playlist, "rate",
-                      f_sign * __MAX( __MIN( pf_rate[i_idx],
-                                             f_rate_max ),
-                                      f_rate_min ) );
-
+        /* compensate for input rounding errors */
+        float r = f_rate * .9;
+        for( size_t i = 1; i < i_rate_count; i++ )
+            if( r <= pf_rate[i] )
+            {
+                f_rate = pf_rate[i - 1];
+                break;
+            }
     }
+
+    var_SetFloat( p_playlist, "rate", f_rate );
     return VLC_SUCCESS;
 }