MP4: recognize 3gp4 brand in debug

3gp4 is not compatible to isom, while 5, 6 and 7 should be
Ref #4979

modules/demux/mp4/libmp4.h

@@ -96,6 +96,7 @@
 #define FOURCC_rtp  VLC_FOURCC( 'r', 't', 'p', ' ' )
 
 #define FOURCC_isom VLC_FOURCC( 'i', 's', 'o', 'm' )
+#define FOURCC_3gp4 VLC_FOURCC( '3', 'g', 'p', '4' )
 #define FOURCC_esds VLC_FOURCC( 'e', 's', 'd', 's' )
 
 #define FOURCC__mp3 VLC_FOURCC( '.', 'm', 'p', '3' )

modules/demux/mp4/mp4.c

@@ -334,6 +334,9 @@ static int Open( vlc_object_t * p_this )
                          "ISO Media file (isom) version %d.",
                          p_ftyp->data.p_ftyp->i_minor_version );
                 break;
+            case( FOURCC_3gp4 ):
+                msg_Dbg( p_demux, "3gp Media file version 4" );
+                break;
             default:
                 msg_Dbg( p_demux,
                          "unrecognized major file specification (%4.4s).",