STL: correctly ignore user-data comments

Ref #10910 and FABst comments

modules/codec/stl.c

@@ -119,12 +119,20 @@ static subpicture_t *Decode(decoder_t *dec, block_t **block)
     if (b->i_buffer < 128)
         goto exit;
 
-    int     payload_size = (b->i_buffer / 128) * 112;
-    uint8_t *payload = malloc(payload_size);
+    int     payload_size = 0;
+    uint8_t *payload = malloc((b->i_buffer / 128) * 112);
     if (!payload)
         goto exit;
+
+    /* */
+    int j = 0;
     for (unsigned i = 0; i < b->i_buffer / 128; i++)
-        memcpy(&payload[112 * i], &b->p_buffer[128 * i + 16], 112);
+    {
+        if( b->p_buffer[128 * i + 3] != 0xfe ) {
+            memcpy(&payload[112 * j++], &b->p_buffer[128 * i + 16], 112);
+            payload_size += 112;
+        }
+    }
 
     sub = decoder_NewSubpicture(dec, NULL);
     if (!sub) {

modules/demux/stl.c

@@ -135,12 +135,13 @@ static int Demux(demux_t *demux)
 {
     demux_sys_t *sys = demux->p_sys;
 
+    int prev_index = 0;
     while(sys->current < sys->count) {
         stl_entry_t *s = &sys->index[sys->current];
         if (s->start > sys->next_date)
             break;
 
-        block_t *b = vlc_stream_Block(demux->s, 128 * s->count);
+        block_t *b = vlc_stream_Block(demux->s, 128 * (s->index - prev_index ));
         if (b) {
             b->i_dts =
             b->i_pts = VLC_TS_0 + s->start;
@@ -149,6 +150,7 @@ static int Demux(demux_t *demux)
             es_out_Send(demux->out, sys->es, b);
         }
         sys->current++;
+        prev_index = s->index;
     }
     return sys->current < sys->count ? 1 : 0;
 }