question: public MP4Reader ( FileInputStream fis ) throws IOException { if ( null == fis ) { log . warn ( "Reader was passed a null file" ) ; log . debug ( "{}" , ToStringBuilder . reflectionToString ( this ) ) ; } this . fis = new MP4DataStream ( fis ) ; channel = fis . getChannel ( ) ; decodeHeader ( ) ; analyzeFrames ( ) ; firstTags . add ( createFileMeta ( ) ) ; createPreStreamingTags ( 0 , false ) ; }
target:  Creates MP4 reader from file input stream, sets up metadata generation flag.