demux: mp4: fix built-in samplesize rounding

modules/demux/mp4/mp4.c

@@ -3036,7 +3036,7 @@ static inline uint32_t MP4_GetFixedSampleSize( const mp4_track_t *p_track,
         case ATOM_twos:
         case ATOM_sowt:
         case ATOM_raw:
-            i_size = p_soun->i_samplesize * p_soun->i_channelcount / 8;
+            i_size = ((p_soun->i_samplesize+7)/8) * p_soun->i_channelcount;
             break;
         default:
             break;