Помогите убрать шум и background из волни wav файла.

Я скачал исходник который нарисует гистограмму вав файла. Помогите убрать шум и задный фон. Вот исходник:

class.wav.php:

Код (Text):

1. <?php
2.  
3. / $File: class.wave.php $Date: 09-02-08 /
4.  
5. class wave {
6.  
7. var $fp, $filesize;
8. var $data, $blocktotal, $blockfmt, $blocksize;
9.  
10. function __construct($file) {
11.  
12.     if(!$this->fp = @fopen($file, 'rb')) {
13.         return false;
14.     }
15.  
16.     $this->filesize = filesize($file);
17.  
18. }
19.  
20. function wavechunk() {
21.  
22.     rewind($this->fp);
23.  
24.     $riff_fmt = 'a4ID/VSize/a4Type';
25.     $riff_cnk = @unpack($riff_fmt, fread($this->fp, 12));
26.  
27.     if($riff_cnk['ID'] != 'RIFF' || $riff_cnk['Type'] != 'WAVE') {
28.         return -1;
29.     }
30.  
31.     $format_header_fmt = 'a4ID/VSize';
32.     $format_header_cnk = @unpack($format_header_fmt, fread($this->fp, 8));
33.  
34.     if($format_header_cnk['ID'] != 'fmt ' || !in_array($format_header_cnk['Size'], array(16, 18))) {
35.         return -2;
36.     }
37.  
38.     $format_fmt = 'vFormatTag/vChannels/VSamplesPerSec/VAvgBytesPerSec/vBlockAlign/vBitsPerSample'.($format_header_cnk['Size'] == 18 ? '/vExtra' : '');
39.     $format_cnk = @unpack($format_fmt, fread($this->fp, $format_header_cnk['Size']));
40.  
41.     if($format_cnk['FormatTag'] != 1) {
42.         return -3;
43.     }
44.  
45.     if(!in_array($format_cnk['Channels'], array(1, 2))) {
46.         return -4;
47.     }
48.  
49.     $fact_fmt = 'a4ID/VSize/Vdata';
50.     $fact_cnk = @unpack($fact_fmt, fread($this->fp, 12));
51.  
52.     if($fact_cnk['ID'] != 'fact') {
53.         fseek($this->fp, ftell($this->fp) - 12);
54.     }
55.  
56.     $data_fmt = 'a4ID/VSize';
57.     $data_cnk = @unpack($data_fmt, fread($this->fp, 8));
58.  
59.     if($data_cnk['ID'] != 'data') {
60.         return -5;
61.     }
62.  
63.     if($data_cnk['Size'] % $format_cnk['BlockAlign'] != 0) {
64.         return -6;
65.     }
66.  
67.     $this->data = fread($this->fp, $data_cnk['Size']);
68.     $this->blockfmt = $format_cnk['Channels'] == 1 ? 'sLeft' : 'sLeft/sRight';
69.  
70.     $this->blocktotal = $data_cnk['Size'] / 4;
71.     $this->blocksize = $format_cnk['BlockAlign'];
72.  
73.     $return = array
74.         (
75.         'Channels' => $format_cnk['Channels'],
76.         'SamplesPerSec' => $format_cnk['SamplesPerSec'],
77.         'AvgBytesPerSec' => $format_cnk['AvgBytesPerSec'],
78.         'BlockAlign' => $format_cnk['BlockAlign'],
79.         'BitsPerSample' => $format_cnk['BitsPerSample'],
80.         'Extra' => $format_cnk['Extra'],
81.         'seconds' => ($data_cnk['Size'] / $format_cnk['AvgBytesPerSec'])
82.         );
83.  
84.     return $return;
85.  
86. }
87.  
88. function waveimage($channel = 'Left', $width = 1000, $height = 300, $bgcolor = array(255, 255, 255), $cenlinecolor = array(180, 180, 180), $imgcolor = array(0, 0, 0)) {
89.  
90.     if(!$this->data) {
91.         if(!is_array($this->wavechunk())) {
92.             return false;
93.         }
94.     }
95.  
96.     $width = max(10, $width);
97.     $height = max(10, $height);
98.  
99.     $border = 1;
100.     $center = ($height - $border * 2) / 2;
101.  
102.     $num_merge = max(1, round($this->blocktotal / $width));
103.     $width = min($width, ceil($this->blocktotal / $num_merge));
104.  
105.     $max = $min = 0;
106.     $x = 1;
107.  
108.     $pixels = array();
109.     $wavetotal = 0;
110.  
111.     for($i = 0; $i < $this->blocktotal; $i++) {
112.         $blocks[] = @unpack($this->blockfmt, substr($this->data, $i * 4, $this->blocksize));
113.     }
114.  
115.     if(!isset($blocks[0][$channel])) {
116.         return false;
117.     }
118.  
119.     for($i = 0; $i < $this->blocktotal; ) {
120.  
121.         for($j = 0; $j < $num_merge; $j++) {
122.             if(isset($blocks[$i + $j])) {
123.                 $wavetotal += $blocks[$i + $j][$channel];
124.             }
125.         }
126.  
127.         $y = round($wavetotal / ($j + 1));
128.         $pixels[] = array($x, $y);
129.  
130.         $max = max($max, $y);
131.         $min = min($min, $y);
132.  
133.         $x++;
134.         $i += $num_merge;
135.         $wavetotal = 0;
136.  
137.     }
138.  
139.     $maxblock = max(abs($max), abs($min));
140.     $zoom = $maxblock / $center;
141.  
142.     $im = imagecreate($width, $height);
143.     $background = imagecolorallocate($im, $bgcolor[0], $bgcolor[1], $bgcolor[2]);
144.  
145.     if($cenlinecolor) {
146.         $cenline = imagecolorallocate($im, $cenlinecolor[0], $cenlinecolor[1], $cenlinecolor[2]);
147.         imageline($im, 1, $center, $width, $center, $cenline);
148.     }
149.  
150.     $color = imagecolorallocate($im, $imgcolor[0], $imgcolor[1], $imgcolor[2]);
151.     $y_old = 0;
152.  
153.     foreach($pixels as $pixel) {
154.  
155.         $y = $center - round($pixel[1] / $zoom);
156.         imagesetpixel($im, $pixel[0], $y, $color);
157.  
158.         if($pixel[0] > 1) {
159.             imageline($im, $pixel[0] - 1, $y_old, $pixel[0], $y, $color);
160.         }
161.  
162.         $y_old = $y;
163.  
164.     }
165.  
166.     return $im;
167.  
168. }
169. }
170.  
171. ?>

example_draw.php:

Код (Text):

1.  <?php
2.  
3. if(($file = $_FILES['upload']) && $file['name'] != 'none' && $file['size'] && $file['tmp_name']) {
4.  
5. include 'class.wave.php';
6.  
7. $wave = new wave($file['tmp_name']);
8. $chunk = $wave->wavechunk();
9.  
10. if(!is_array($chunk)) {
11.     exit('This is not a wav file.');
12. }
13.  
14. if($chunk['seconds'] > 999) {
15.  
16.     echo "The wav is too long.\r\n\r\n";
17.     print_r($chunk);
18.  
19. } else {
20.  
21.     set_time_limit(999);
22.  
23.     if($im = $wave->waveimage()) {
24.         header('Content-Type: image/png');
25.         imagepng($im, 'simple.png');
26.  
27.         } else {
28.         echo "wrong!\r\n\r\n";
29.         print_r($chunk);
30.     }
31.  
32. }
33. } else {
34.  
35. ?>
36.  
37. <form action="?" id="upload_form" method="post" enctype="multipart/form-data"> <input type="file" name="upload" /><br /> <button type="submit">Submit Wav file</button> </form>
38.  
39. <?php
40.  
41. }
42.  
43. ?>