problem: node.js make memory leaks about child_proces

gistfile1.js

//// problem: node.js make memory leaks about child_proces
//
// the javascript doing it tha same to the shell code
// $ cat mako_* | ./ffmpeg -y -f image2pipe -r 1 -vcodec bmp -r 29.7 -i - -vcodec utvideo movie.avi


var ffmpeg = require('basicFFmpeg');
var fs = require('fs');
var sprintf = require('sprintf').sprintf;
var spawn = require('child_process').spawn,
    exec = require('child_process').exec;


function genProcArgs(processor) {
  var args = ['-y', '-f', 'image2pipe', '-r', '1', '-vcodec', 'bmp', '-r', '29.7', '-i', '-', '-vcodec', 'utvideo', '-f', 'avi'];
//    args.push('pipe:1');
    args.push("test.avi");
	return args;
}

var proc = spawn('ffmpeg', genProcArgs());

for(var j = 0; j < 1000; j++) {
	for(var i = 0; i <= 12; i++) {
		var path = sprintf("mako_%04d.bmp", i);
		var data = fs.readFileSync(path);
		console.log(j, i);

		// 1. writing out to ffmpeg process, occars memory leaks
		proc.stdin.write(data);

		//// 2. writing out to a local file, no memory leaks
		// fs.appendFileSync("m.bmp", data);
	}
}
proc.stdin.end();