ILIAS  release_5-1 Revision 5.0.0-5477-g43f3e3fab5
getid3_amr Class Reference

getID3() by James Heinrich info@.nosp@m.geti.nosp@m.d3.or.nosp@m.g // More...

+ Inheritance diagram for getid3_amr:
+ Collaboration diagram for getid3_amr:

Public Member Functions

 Analyze ()
 
 amr_mode_bitrate ($key)
 
 amr_mode_bytes_per_frame ($key)
 
- Public Member Functions inherited from getid3_handler
 __construct (getID3 $getid3, $call_module=null)
 
 Analyze ()
 
 AnalyzeString ($string)
 
 setStringMode ($string)
 
 saveAttachment ($name, $offset, $length, $image_mime=null)
 

Additional Inherited Members

- Protected Member Functions inherited from getid3_handler
 ftell ()
 
 fread ($bytes)
 
 fseek ($bytes, $whence=SEEK_SET)
 
 feof ()
 
 isDependencyFor ($module)
 
 error ($text)
 
 warning ($text)
 
 notice ($text)
 
- Protected Attributes inherited from getid3_handler
 $getid3
 
 $data_string_flag = false
 
 $data_string = ''
 
 $data_string_position = 0
 
 $data_string_length = 0
 

Detailed Description

getID3() by James Heinrich info@.nosp@m.geti.nosp@m.d3.or.nosp@m.g //

Definition at line 18 of file module.audio.amr.php.

Member Function Documentation

◆ amr_mode_bitrate()

getid3_amr::amr_mode_bitrate (   $key)

Definition at line 68 of file module.audio.amr.php.

68  {
69  static $amr_mode_bitrate = array(
70  0 => 4750,
71  1 => 5150,
72  2 => 5900,
73  3 => 6700,
74  4 => 7400,
75  5 => 7950,
76  6 => 10200,
77  7 => 12200,
78  );
79  return (isset($amr_mode_bitrate[$key]) ? $amr_mode_bitrate[$key] : false);
80  }

◆ amr_mode_bytes_per_frame()

getid3_amr::amr_mode_bytes_per_frame (   $key)

Definition at line 82 of file module.audio.amr.php.

Referenced by Analyze().

82  {
83  static $amr_mode_bitrate = array(
84  0 => 13, // 1-byte frame header + 95 bits [padded to: 12 bytes] audio data
85  1 => 14, // 1-byte frame header + 103 bits [padded to: 13 bytes] audio data
86  2 => 16, // 1-byte frame header + 118 bits [padded to: 15 bytes] audio data
87  3 => 18, // 1-byte frame header + 134 bits [padded to: 17 bytes] audio data
88  4 => 20, // 1-byte frame header + 148 bits [padded to: 19 bytes] audio data
89  5 => 21, // 1-byte frame header + 159 bits [padded to: 20 bytes] audio data
90  6 => 27, // 1-byte frame header + 204 bits [padded to: 26 bytes] audio data
91  7 => 32, // 1-byte frame header + 244 bits [padded to: 31 bytes] audio data
92  );
93  return (isset($amr_mode_bitrate[$key]) ? $amr_mode_bitrate[$key] : false);
94  }
+ Here is the caller graph for this function:

◆ Analyze()

getid3_amr::Analyze ( )

Definition at line 21 of file module.audio.amr.php.

References $info, amr_mode_bytes_per_frame(), getid3_handler\feof(), getid3_handler\fread(), getid3_handler\fseek(), and getid3_lib\PrintHexBytes().

21  {
22  $info = &$this->getid3->info;
23 
24  $this->fseek($info['avdataoffset']);
25  $AMRheader = $this->fread(6);
26 
27  $magic = '#!AMR'."\x0A";
28  if (substr($AMRheader, 0, 6) != $magic) {
29  $info['error'][] = 'Expecting "'.getid3_lib::PrintHexBytes($magic).'" at offset '.$info['avdataoffset'].', found "'.getid3_lib::PrintHexBytes(substr($AMRheader, 0, 6)).'"';
30  return false;
31  }
32 
33  // shortcut
34  $info['amr'] = array();
35  $thisfile_amr = &$info['amr'];
36 
37  $info['fileformat'] = 'amr';
38  $info['audio']['dataformat'] = 'amr';
39  $info['audio']['bitrate_mode'] = 'vbr'; // within a small predefined range: 4.75kbps to 12.2kbps
40  $info['audio']['bits_per_sample'] = 13; // http://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec: "Sampling frequency 8 kHz/13-bit (160 samples for 20 ms frames), filtered to 200–3400 Hz"
41  $info['audio']['sample_rate'] = 8000; // http://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec: "Sampling frequency 8 kHz/13-bit (160 samples for 20 ms frames), filtered to 200–3400 Hz"
42  $info['audio']['channels'] = 1;
43  $thisfile_amr['frame_mode_count'] = array(0=>0, 1=>0, 2=>0, 3=>0, 4=>0, 5=>0, 6=>0, 7=>0);
44 
45  $buffer = '';
46  do {
47  if ((strlen($buffer) < $this->getid3->fread_buffer_size()) && !feof($this->getid3->fp)) {
48  $buffer .= $this->fread($this->getid3->fread_buffer_size() * 2);
49  }
50  $AMR_frame_header = ord(substr($buffer, 0, 1));
51  $codec_mode_request = ($AMR_frame_header & 0x78) >> 3; // The 2nd bit through 5th bit (counting the most significant bit as the first bit) comprise the CMR (Codec Mode Request), values 0-7 being valid for AMR. The top bit of the CMR can actually be ignored, though it is used when AMR forms RTP payloads. The lower 3-bits of the header are reserved and are not used. Viewing the header from most significant bit to least significant bit, the encoding is XCCCCXXX, where Xs are reserved (typically 0) and the Cs are the CMR.
52  if ($codec_mode_request > 7) {
53  $info['error'][] = '';
54  break;
55  }
56  $thisfile_amr['frame_mode_count'][$codec_mode_request]++;
57  $buffer = substr($buffer, $this->amr_mode_bytes_per_frame($codec_mode_request));
58  } while (strlen($buffer) > 0);
59 
60  $info['playtime_seconds'] = array_sum($thisfile_amr['frame_mode_count']) * 0.020; // each frame contain 160 samples and is 20 milliseconds long
61  $info['audio']['bitrate'] = (8 * ($info['avdataend'] - $info['avdataoffset'])) / $info['playtime_seconds']; // bitrate could be calculated from average bitrate by distributation of frame types. That would give effective audio bitrate, this gives overall file bitrate which will be a little bit higher since every frame will waste 8 bits for header, plus a few bits for octet padding
62  $info['bitrate'] = $info['audio']['bitrate'];
63 
64  return true;
65  }
$info
Definition: example_052.php:80
fread($bytes)
Definition: getid3.php:1685
amr_mode_bytes_per_frame($key)
fseek($bytes, $whence=SEEK_SET)
Definition: getid3.php:1697
PrintHexBytes($string, $hex=true, $spaces=true, $htmlsafe=true)
Definition: getid3.lib.php:17
+ Here is the call graph for this function:

The documentation for this class was generated from the following file: