diff --git a/modules/demux/mp4/libmp4.c b/modules/demux/mp4/libmp4.c
index 4987588bd34e..abc2691eb823 100644
--- a/modules/demux/mp4/libmp4.c
+++ b/modules/demux/mp4/libmp4.c
@@ -1110,46 +1110,45 @@ static int MP4_ReadBox_trun(  stream_t *p_stream, MP4_Box_t *p_box )
     uint32_t count;
 
     MP4_READBOX_ENTER( MP4_Box_data_trun_t, MP4_FreeBox_trun );
-
-    MP4_GETVERSIONFLAGS( p_box->data.p_trun );
+    MP4_Box_data_trun_t *p_trun = p_box->data.p_trun;
+    MP4_GETVERSIONFLAGS( p_trun );
     MP4_GET4BYTES( count );
 
-    if( p_box->data.p_trun->i_flags & MP4_TRUN_DATA_OFFSET )
-        MP4_GET4BYTES( p_box->data.p_trun->i_data_offset );
-    if( p_box->data.p_trun->i_flags & MP4_TRUN_FIRST_FLAGS )
-        MP4_GET4BYTES( p_box->data.p_trun->i_first_sample_flags );
+    if( p_trun->i_flags & MP4_TRUN_DATA_OFFSET )
+        MP4_GET4BYTES( p_trun->i_data_offset );
+    if( p_trun->i_flags & MP4_TRUN_FIRST_FLAGS )
+        MP4_GET4BYTES( p_trun->i_first_sample_flags );
 
     if( UINT64_C(16) * count > i_read )
         MP4_READBOX_EXIT( 0 );
 
-    p_box->data.p_trun->p_samples = vlc_alloc( count,
-                                        sizeof(MP4_descriptor_trun_sample_t) );
-    if ( p_box->data.p_trun->p_samples == NULL )
+    p_trun->p_samples = vlc_alloc( count, sizeof(MP4_descriptor_trun_sample_t) );
+    if ( p_trun->p_samples == NULL )
         MP4_READBOX_EXIT( 0 );
-    p_box->data.p_trun->i_sample_count = count;
+    p_trun->i_sample_count = count;
 
     for( unsigned int i = 0; i < count; i++ )
     {
-        MP4_descriptor_trun_sample_t *p_sample = &p_box->data.p_trun->p_samples[i];
-        if( p_box->data.p_trun->i_flags & MP4_TRUN_SAMPLE_DURATION )
+        MP4_descriptor_trun_sample_t *p_sample = &p_trun->p_samples[i];
+        if( p_trun->i_flags & MP4_TRUN_SAMPLE_DURATION )
             MP4_GET4BYTES( p_sample->i_duration );
-        if( p_box->data.p_trun->i_flags & MP4_TRUN_SAMPLE_SIZE )
+        if( p_trun->i_flags & MP4_TRUN_SAMPLE_SIZE )
             MP4_GET4BYTES( p_sample->i_size );
-        if( p_box->data.p_trun->i_flags & MP4_TRUN_SAMPLE_FLAGS )
+        if( p_trun->i_flags & MP4_TRUN_SAMPLE_FLAGS )
             MP4_GET4BYTES( p_sample->i_flags );
-        if( p_box->data.p_trun->i_flags & MP4_TRUN_SAMPLE_TIME_OFFSET )
+        if( p_trun->i_flags & MP4_TRUN_SAMPLE_TIME_OFFSET )
             MP4_GET4BYTES( p_sample->i_composition_time_offset.v0 );
     }
 
 #ifdef MP4_ULTRA_VERBOSE
     msg_Dbg( p_stream, "read box: \"trun\" version %u flags 0x%x sample count %"PRIu32,
-                  p_box->data.p_trun->i_version,
-                  p_box->data.p_trun->i_flags,
-                  p_box->data.p_trun->i_sample_count );
+                  p_trun->i_version,
+                  p_trun->i_flags,
+                  p_trun->i_sample_count );
 
     for( unsigned int i = 0; i < count; i++ )
     {
-        MP4_descriptor_trun_sample_t *p_sample = &p_box->data.p_trun->p_samples[i];
+        MP4_descriptor_trun_sample_t *p_sample = &p_trun->p_samples[i];
         msg_Dbg( p_stream, "read box: \"trun\" sample %4.4u flags 0x%x "\
             "duration %"PRIu32" size %"PRIu32" composition time offset %"PRIu32,
                         i, p_sample->i_flags, p_sample->i_duration,