Modifying hex format files

[garyshall]

I need a little help getting started. My application requires modifying a value in the header of a hex-format MIDI file to change its play tempo. Any advice on poking values into a fixed location of a binary-hex file would be appreciated.

thanks!

[HalfaBee]

Try this
It will open up the file and write over the location $addr with $ byte.
HalfaBee

<?
$addr = 0;  // place of byte top change
$byte = chr( 0x11 ); // value to change it to

$fp = fopen( "file.mid","r+" );
if( $fp )
{
 if( fseek( $fp , $addr ) )
  fwrite( $fp , $byte , 1 );
}
fclose($fp);
?>

[garyshall]

Thanks, HalfaBee. This is just what I was looking for.