demux: mp4: fix TRUN composition time signedness

modules/demux/mp4/libmp4.h

@@ -953,7 +953,7 @@ typedef struct MP4_descriptor_trun_sample_t
     uint32_t i_duration;
     uint32_t i_size;
     uint32_t i_flags;
-    uint32_t i_composition_time_offset;
+    uint32_t i_composition_time_offset; /* version == 0 ? signed : unsigned */
 } MP4_descriptor_trun_sample_t;
 
 typedef struct MP4_Box_data_trun_s

modules/demux/mp4/mp4.c

@@ -3933,8 +3933,10 @@ static int MP4_frg_GetChunk( demux_t *p_demux, MP4_Box_t *p_chunk, unsigned *i_t
 
         if( ret->p_sample_offset_pts )
         {
-            ret->p_sample_offset_pts[i] =
-                        p_trun_data->p_samples[i].i_composition_time_offset;
+            if ( p_trun_data->i_version == 0 )
+                ret->p_sample_offset_pts[i] = (int32_t) p_trun_data->p_samples[i].i_composition_time_offset;
+            else
+                ret->p_sample_offset_pts[i] = __MIN( INT32_MAX, p_trun_data->p_samples[i].i_composition_time_offset );
         }
 
         if( p_trun_data->i_flags & MP4_TRUN_SAMPLE_SIZE )