Do not decode subtitles too much in advanced.

It avoids loosing subtitles with the messages
"main subpicture error: subpicture heap full".
(cherry picked from commit 34f25416)

include/vlc_config.h

@@ -131,6 +131,14 @@
 /* Max acceptable resampling (in %) */
 #define AOUT_MAX_RESAMPLING             10
 
+/*****************************************************************************
+ * SPU configuration
+ *****************************************************************************/
+
+/* Buffer must avoid arriving more than SPU_MAX_PREPARE_TIME in advanced to
+ * the SPU */
+#define SPU_MAX_PREPARE_TIME ((mtime_t)(0.5*CLOCK_FREQ))
+
 /*****************************************************************************
  * Video configuration
  *****************************************************************************/

src/input/decoder.c

@@ -1570,6 +1570,12 @@ static void DecoderPlaySpu( decoder_t *p_dec, subpicture_t *p_subpic,
 
         vlc_mutex_unlock( &p_owner->lock );
 
+        if( p_subpic->i_start <= VLC_TS_INVALID )
+            b_reject = true;
+
+        DecoderWaitDate( p_dec, &b_reject,
+                         p_subpic->i_start - SPU_MAX_PREPARE_TIME );
+
         if( !b_reject )
             spu_DisplaySubpicture( p_vout->p_spu, p_subpic );
         else

src/video_output/vout_subpictures.c

@@ -44,8 +44,9 @@
 /*****************************************************************************
  * Local prototypes
  *****************************************************************************/
+
 /* Number of simultaneous subpictures */
-#define VOUT_MAX_SUBPICTURES (VOUT_MAX_PICTURES)
+#define VOUT_MAX_SUBPICTURES (__MAX(VOUT_MAX_PICTURES, SPU_MAX_PREPARE_TIME/5000))
 
 #define VLC_FOURCC_YUVP VLC_FOURCC('Y','U','V','P')
 #define VLC_FOURCC_YUVA VLC_FOURCC('Y','U','V','A')