用Php分析並繪製音訊檔案的波形圖,網路上還是很少見到。其實只要依照wav檔案的規範,用Php的fseek,fopen,fopen,pack/unpack等函數,以及強大的gd圖形函式庫,這些都是很容易的。很多人可能對pack/unpack函數不熟悉;這其實是Php借用perl的,他們提供了使用腳本語言存取複雜二進位資料結構的方法。我的這段簡化的程式只能處理PCM格式的RIFF音訊檔(這也是最常見的wav格式) ,不限聲道,但是比特率(BitsPerSample)最好是16。
這裡有wave file format 和MicroSoft wave soundfile format可以參考。這裡是一個實際的例子(下載放大看)
以下是引用片段:
1 <?Php
2
3 function wav_graph($file, $f=0, $w=0)
4 {
5 global $DATA_DIR;
6
7 if(!is_file($file)) return 0;
8 $fp = fopen($DATA_DIR.$file , 'r');
9 $raw = fread($fp, 36);
10 $str = '';
11 $header = unpack('A4Riff/VSize/A4Wav/A4Head/VHeadSize/vPCM/vChannels/VSampleRate/VByteRate/ vBlockAlign/vSampleBits', $raw);
12 foreach($header as $k=>$v)
13 $str .= $k.': '. $v.' ';
14 fseek($fp, 36 + $header ['HeadSize'] - 16);
15 $raw = fread($fp, 8);
16 $data = unpack('A4Data/VDataSize', $raw);
17 foreach($data as $k=>$v)
18 $str .= $k.': '. $v.' ';
19
20 $b = $header['SampleBits'];
21 $c = $header['Channels'];
22 $l = $b * $c / 8; // sample frame length in bytes
23 $s = $data['DataSize'] / $l; // total number of samples
24 $r = $header['SampleRate'];
25 if($f ) $h = pow(2, $b) / $f;
26 else { $h = 200; $f = pow(2, $b - 1) / $h; }
27 if($w == 0) $ w = round($r / 1000); // default to show 1k sample frames per minute
28
29 header("Content-type: image/png");
30 $im = imagecreate($s / $w, $h * $c * 2);
31 imagecolorallocate($im, 0xff, 0xff, 0xff); // white bg
32 $color = imagecolorallocate($im, 0, 0, 255); // black
33 //imagestring($im, 5, 5, 5, $str, $color);
34
35 $x=0; $y = array(); $yn = array();
36 for($i = 0; $i < $c; $i++ ) $y[$i] = $h * $i + $h;
37 $n = $l * $w;
38 while(1)
39 {
40 if($s == 0) break;
41 if($s < $n) $n = $s;
42 $samples = fread($fp, 1000 * $n);
43 if($samples === FALSE) break;
44 $packed = unpack("s*", $samples );
45 foreach($packed as $k=>$v)
46 {
47 $cnt = ($k-1) % ($w * $l) ;
48 if( $cnt > $c - 1) continue;
49 $yn[$cnt] = $h * $cnt + $h - $v / $f;
50 imageline($im, $x, $y[$cnt], $x+1, $yn[$cnt], $color);
51 $y[$cnt] = $yn[$cnt];
52 $x++;
53 }
54 $s -= $n;
55 }
56
57 imagepng($im);
58 imagedestroy($im);
59 }
60
61 //wav_graph('audio2.wav');
62 ?>