This file is indexed.

/usr/share/pyshared/eyeD3/mp3.py is in python-eyed3 0.6.18-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
################################################################################
#  Copyright (C) 2002-2005,2007  Travis Shirk <travis@pobox.com>
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software
#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
################################################################################
from binfuncs import *;
from utils import *;
from math import log10

#######################################################################
class Mp3Exception(Exception):
   '''Error reading mp3'''


#                   MPEG1  MPEG2  MPEG2.5
SAMPLE_FREQ_TABLE = ((44100, 22050, 11025),
                     (48000, 24000, 12000),
                     (32000, 16000, 8000),
                     (None,  None,  None));

#              V1/L1  V1/L2 V1/L3 V2/L1 V2/L2&L3 
BIT_RATE_TABLE = ((0,    0,    0,    0,    0),
                  (32,   32,   32,   32,   8),
                  (64,   48,   40,   48,   16),
                  (96,   56,   48,   56,   24),
                  (128,  64,   56,   64,   32),
                  (160,  80,   64,   80,   40),
                  (192,  96,   80,   96,   44),
                  (224,  112,  96,   112,  56),
                  (256,  128,  112,  128,  64),
                  (288,  160,  128,  144,  80),
                  (320,  192,  160,  160,  96),
                  (352,  224,  192,  176,  112),
                  (384,  256,  224,  192,  128),
                  (416,  320,  256,  224,  144),
                  (448,  384,  320,  256,  160),
                  (None, None, None, None, None));

#                             L1    L2    L3
TIME_PER_FRAME_TABLE = (None, 384, 1152, 1152);

# Emphasis constants
EMPHASIS_NONE = "None";
EMPHASIS_5015 = "50/15 ms";
EMPHASIS_CCIT = "CCIT J.17";

# Mode constants
MODE_STEREO              = "Stereo";
MODE_JOINT_STEREO        = "Joint stereo";
MODE_DUAL_CHANNEL_STEREO = "Dual channel stereo";
MODE_MONO                = "Mono";

# Xing flag bits
FRAMES_FLAG    = 0x0001
BYTES_FLAG     = 0x0002
TOC_FLAG       = 0x0004
VBR_SCALE_FLAG = 0x0008

#######################################################################
# Pass in a 4 byte integer to determine if it matches a valid mp3 frame
# header.
def is_valid_mp_header(header):
    # Test for the mp3 frame sync: 11 set bits.
    sync = (header >> 16)
    if sync & 0xFFE0 != 0xFFE0:
        # ffe0 is 11 sync bits, and supports identifying mpeg v2.5
        return False

    version = (header >> 19) & 0x3
    if version == 1:
        # This is a "reserved" version
        TRACE_MSG("invalid mpeg version")
        return False

    layer = (header >> 17) & 0x3
    if layer == 0:
        # This is a "reserved" layer
        TRACE_MSG("invalid mpeg layer")
        return False

    bitrate = (header >> 12) & 0xf
    if bitrate in (0, 0xf):
        # free and bad bitrate values
        TRACE_MSG("invalid mpeg bitrate")
        return False

    sample_rate = (header >> 10) & 0x3
    if sample_rate == 0x3:
        # this is a "reserved" sample rate
        TRACE_MSG("invalid mpeg sample rate")
        return False

    return True

def find_header(fp, start_pos=0):
    def find_sync(fp, start_pos=0):
        CHUNK_SIZE = 65536

        fp.seek(start_pos)
        data = fp.read(CHUNK_SIZE)
        data_len = len(data)

        while data:
            sync_pos = data.find('\xff', 0)
            if sync_pos >= 0:
                header = data[sync_pos:sync_pos + 4]
                if len(header) == 4:
                    return (start_pos + sync_pos, header)
            data = fp.read(CHUNK_SIZE)
            data_len = len(data)
        return (None, None)
    sync_pos, header_bytes = find_sync(fp, start_pos)
    while sync_pos is not None:
        header = bytes2dec(header_bytes)
        if is_valid_mp_header(header):
            return (sync_pos, header, header_bytes)
        sync_pos, header_bytes = find_sync(fp, start_pos + sync_pos + 2)
    return (None, None, None)

def computeTimePerFrame(frameHeader):
   return (float(TIME_PER_FRAME_TABLE[frameHeader.layer]) /
           float(frameHeader.sampleFreq))

#######################################################################
class Header:
   def __init__(self, header_data=None):
       self.version = None
       self.layer = None
       self.errorProtection = None
       self.bitRate = None
       self.playTime = None
       self.sampleFreq = None
       self.padding = None
       self.privateBit = None
       self.copyright = None
       self.original = None
       self.emphasis = None
       self.mode = None
       # This value is left as is: 0<=modeExtension<=3.
       # See http://www.dv.co.yu/mpgscript/mpeghdr.htm for how to interpret
       self.modeExtension = None

       if header_data:
           self.decode(header_data)

   # This may throw an Mp3Exception if the header is malformed.
   def decode(self, header):
      if not is_valid_mp_header(header):
         raise Mp3Exception("Invalid MPEG header");

      # MPEG audio version from bits 19 and 20.
      version = (header >> 19) & 0x3
      self.version = [2.5, None, 2.0, 1.0][version]
      if self.version is None:
         raise Mp3Exception("Illegal MPEG version");

      # MPEG layer
      self.layer = 4 - ((header >> 17) & 0x3)
      if self.layer == 4:
         raise Mp3Exception("Illegal MPEG layer");

      # Decode some simple values.
      self.errorProtection = not (header >> 16) & 0x1;
      self.padding = (header >> 9) & 0x1;
      self.privateBit = (header >> 8) & 0x1;
      self.copyright = (header >> 3) & 0x1;
      self.original = (header >> 2) & 0x1;

      # Obtain sampling frequency.
      sampleBits = (header >> 10) & 0x3;
      if self.version == 2.5:
         freqCol = 2;
      else:
         freqCol = int(self.version - 1);
      self.sampleFreq = SAMPLE_FREQ_TABLE[sampleBits][freqCol];
      if not self.sampleFreq:
         raise Mp3Exception("Illegal MPEG sampling frequency");

      # Compute bitrate.
      bitRateIndex = (header >> 12) & 0xf;
      if int(self.version) == 1 and self.layer == 1:
         bitRateCol = 0;
      elif int(self.version) == 1 and self.layer == 2:
         bitRateCol = 1;
      elif int(self.version) == 1 and self.layer == 3:
         bitRateCol = 2;
      elif int(self.version) == 2 and self.layer == 1:
         bitRateCol = 3;
      elif int(self.version) == 2 and (self.layer == 2 or \
                                       self.layer == 3):
         bitRateCol = 4;
      else:
         raise Mp3Exception("Mp3 version %f and layer %d is an invalid "\
                            "combination" % (self.version, self.layer));
      self.bitRate = BIT_RATE_TABLE[bitRateIndex][bitRateCol];
      if self.bitRate == None:
         raise Mp3Exception("Invalid bit rate");
      # We know know the bit rate specified in this frame, but if the file
      # is VBR we need to obtain the average from the Xing header.
      # This is done by the caller since right now all we have is the frame
      # header.

      # Emphasis; whatever that means??
      emph = header & 0x3;
      if emph == 0:
         self.emphasis = EMPHASIS_NONE;
      elif emph == 1:
         self.emphasis = EMPHASIS_5015;
      elif emph == 2:
         self.emphasis = EMPHASIS_CCIT;
      elif strictID3():
         raise Mp3Exception("Illegal mp3 emphasis value: %d" % emph);

      # Channel mode.
      modeBits = (header >> 6) & 0x3;
      if modeBits == 0:
         self.mode = MODE_STEREO;
      elif modeBits == 1:
         self.mode = MODE_JOINT_STEREO;
      elif modeBits == 2:
         self.mode = MODE_DUAL_CHANNEL_STEREO;
      else:
         self.mode = MODE_MONO;
      self.modeExtension = (header >> 4) & 0x3;

      # Layer II has restrictions wrt to mode and bit rate.  This code
      # enforces them.
      if self.layer == 2:
         m = self.mode;
         br = self.bitRate;
         if (br == 32 or br == 48 or br == 56 or br == 80) and \
            (m != MODE_MONO):
            raise Mp3Exception("Invalid mode/bitrate combination for layer "\
                               "II");
         if (br == 224 or br == 256 or br == 320 or br == 384) and \
            (m == MODE_MONO):
            raise Mp3Exception("Invalid mode/bitrate combination for layer "\
                               "II");

      br = self.bitRate * 1000;
      sf = self.sampleFreq;
      p  = self.padding;
      if self.layer == 1:
         # Layer 1 uses 32 bit slots for padding.
         p  = self.padding * 4;
         self.frameLength = int((((12 * br) / sf) + p) * 4);
      else:
         # Layer 2 and 3 uses 8 bit slots for padding.
         p  = self.padding * 1;
         self.frameLength = int(((144 * br) / sf) + p);

      # Dump the state.
      TRACE_MSG("MPEG audio version: " + str(self.version));
      TRACE_MSG("MPEG audio layer: " + ("I" * self.layer));
      TRACE_MSG("MPEG sampling frequency: " + str(self.sampleFreq));
      TRACE_MSG("MPEG bit rate: " + str(self.bitRate));
      TRACE_MSG("MPEG channel mode: " + self.mode);
      TRACE_MSG("MPEG channel mode extension: " + str(self.modeExtension));
      TRACE_MSG("MPEG CRC error protection: " + str(self.errorProtection));
      TRACE_MSG("MPEG original: " + str(self.original));
      TRACE_MSG("MPEG copyright: " + str(self.copyright));
      TRACE_MSG("MPEG private bit: " + str(self.privateBit));
      TRACE_MSG("MPEG padding: " + str(self.padding));
      TRACE_MSG("MPEG emphasis: " + str(self.emphasis));
      TRACE_MSG("MPEG frame length: " + str(self.frameLength));

#######################################################################
class XingHeader:
   numFrames = int();
   numBytes = int();
   toc = [0] * 100;
   vbrScale = int();

   # Pass in the first mp3 frame from the file as a byte string.
   # If an Xing header is present in the file it'll be in the first mp3
   # frame.  This method returns true if the Xing header is found in the
   # frame, and false otherwise.
   def decode(self, frame):
      # mp3 version
      version = (ord(frame[1]) >> 3) & 0x1;
      # channel mode.
      mode = (ord(frame[3]) >> 6) & 0x3;

      # Find the start of the Xing header.
      if version:
         if mode != 3:
            pos = 32 + 4;
         else:
            pos = 17 + 4;
      else:
         if mode != 3:
            pos = 17 + 4;
         else:
            pos = 9 + 4;
      head = frame[pos:pos+4]
      self.vbr = (head == 'Xing') and True or False
      if head not in ['Xing', 'Info']:
          return 0
      TRACE_MSG("%s header detected @ %x" % (head, pos));
      pos += 4;

      # Read Xing flags.
      headFlags = bin2dec(bytes2bin(frame[pos:pos + 4]));
      pos += 4;
      TRACE_MSG("%s header flags: 0x%x" % (head, headFlags));

      # Read frames header flag and value if present
      if headFlags & FRAMES_FLAG:
         self.numFrames = bin2dec(bytes2bin(frame[pos:pos + 4]));
         pos += 4;
         TRACE_MSG("%s numFrames: %d" % (head, self.numFrames));

      # Read bytes header flag and value if present
      if headFlags & BYTES_FLAG:
         self.numBytes = bin2dec(bytes2bin(frame[pos:pos + 4]));
         pos += 4;
         TRACE_MSG("%s numBytes: %d" % (head, self.numBytes));

      # Read TOC header flag and value if present
      if headFlags & TOC_FLAG:
         i = 0;
         self.toc = frame[pos:pos + 100];
         pos += 100;
         TRACE_MSG("%s TOC (100 bytes): PRESENT" % head);
      else:
         TRACE_MSG("%s TOC (100 bytes): NOT PRESENT" % head);

      # Read vbr scale header flag and value if present
      if headFlags & VBR_SCALE_FLAG and head == 'Xing':
         self.vbrScale = bin2dec(bytes2bin(frame[pos:pos + 4]));
         pos += 4;
         TRACE_MSG("%s vbrScale: %d" % (head, self.vbrScale));

      return 1;

#######################################################################
class LameTag(dict):
   """Mp3 Info tag (AKA LAME Tag)

   Lame (and some other encoders) write a tag containing various bits of info
   about the options used at encode time.  If available, the following are
   parsed and stored in the LameTag dict:

   encoder_version: short encoder version [str]
   tag_revision:    revision number of the tag [int]
   vbr_method:      VBR method used for encoding [str]
   lowpass_filter:  lowpass filter frequency in Hz [int]
   replaygain:      if available, radio and audiofile gain (see below) [dict]
   encoding_flags:  encoding flags used [list]
   nogap:           location of gaps when --nogap was used [list]
   ath_type:        ATH type [int]
   bitrate:         bitrate and type (Constant, Target, Minimum) [tuple]
   encoder_delay:   samples added at the start of the mp3 [int]
   encoder_padding: samples added at the end of the mp3 [int]
   noise_shaping:   noise shaping method [int]
   stereo_mode:     stereo mode used [str]
   unwise_settings: whether unwise settings were used [boolean]
   sample_freq:     source sample frequency [str]
   mp3_gain:        mp3 gain adjustment (rarely used) [float]
   preset:          preset used [str]
   surround_info:   surround information [str]
   music_length:    length in bytes of original mp3 [int]
   music_crc:       CRC-16 of the mp3 music data [int]
   infotag_crc:     CRC-16 of the info tag [int]

   Prior to ~3.90, Lame simply stored the encoder version in the first frame.
   If the infotag_crc is invalid, then we try to read this version string.  A
   simple way to tell if the LAME Tag is complete is to check for the
   infotag_crc key.

   Replay Gain data is only available since Lame version 3.94b.  If set, the
   replaygain dict has the following structure:

      peak_amplitude: peak signal amplitude [float]
      radio:
         name:       name of the gain adjustment [str]
         adjustment: gain adjustment [float]
         originator: originator of the gain adjustment [str]
      audiofile: [same as radio]

   Note that as of 3.95.1, Lame uses 89dB as a reference level instead of the
   83dB that is specified in the Replay Gain spec.  This is not automatically
   compensated for.  You can do something like this if you want:

      import eyeD3
      af = eyeD3.Mp3AudioFile('/path/to/some.mp3')
      lamever = af.lameTag['encoder_version']
      name, ver = lamever[:4], lamever[4:]
      gain = af.lameTag['replaygain']['radio']['adjustment']
      if name == 'LAME' and eyeD3.mp3.lamevercmp(ver, '3.95') > 0:
          gain -= 6

   Radio and Audiofile Replay Gain are often referrered to as Track and Album
   gain, respectively.  See http://replaygain.hydrogenaudio.org/ for futher
   details on Replay Gain.

   See http://gabriel.mp3-tech.org/mp3infotag.html for the gory details of the
   LAME Tag.
   """

   # from the LAME source:
   # http://lame.cvs.sourceforge.net/*checkout*/lame/lame/libmp3lame/VbrTag.c
   _crc16_table = [
      0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
      0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
      0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
      0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
      0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
      0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
      0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
      0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
      0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
      0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
      0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
      0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
      0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
      0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
      0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
      0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
      0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
      0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
      0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
      0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
      0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
      0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
      0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
      0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
      0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
      0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
      0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
      0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
      0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
      0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
      0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
      0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040]

   ENCODER_FLAGS = {
      'NSPSYTUNE'   : 0x0001,
      'NSSAFEJOINT' : 0x0002,
      'NOGAP_NEXT'  : 0x0004,
      'NOGAP_PREV'  : 0x0008,}

   PRESETS = {
      0:    'Unknown',
      # 8 to 320 are reserved for ABR bitrates
      410:  'V9',
      420:  'V8',
      430:  'V7',
      440:  'V6',
      450:  'V5',
      460:  'V4',
      470:  'V3',
      480:  'V2',
      490:  'V1',
      500:  'V0',
      1000: 'r3mix',
      1001: 'standard',
      1002: 'extreme',
      1003: 'insane',
      1004: 'standard/fast',
      1005: 'extreme/fast',
      1006: 'medium',
      1007: 'medium/fast',}

   REPLAYGAIN_NAME = {
      0: 'Not set',
      1: 'Radio',
      2: 'Audiofile',}

   REPLAYGAIN_ORIGINATOR = {
      0:   'Not set',
      1:   'Set by artist',
      2:   'Set by user',
      3:   'Set automatically',
      100: 'Set by simple RMS average',}

   SAMPLE_FREQUENCIES = {
      0: '<= 32 kHz',
      1: '44.1 kHz',
      2: '48 kHz',
      3: '> 48 kHz',}

   STEREO_MODES = {
      0: 'Mono',
      1: 'Stereo',
      2: 'Dual',
      3: 'Joint',
      4: 'Force',
      5: 'Auto',
      6: 'Intensity',
      7: 'Undefined',}

   SURROUND_INFO = {
      0: 'None',
      1: 'DPL encoding',
      2: 'DPL2 encoding',
      3: 'Ambisonic encoding',
      8: 'Reserved',}

   VBR_METHODS = {
      0:  'Unknown',
      1:  'Constant Bitrate',
      2:  'Average Bitrate',
      3:  'Variable Bitrate method1 (old/rh)',
      4:  'Variable Bitrate method2 (mtrh)',
      5:  'Variable Bitrate method3 (mt)',
      6:  'Variable Bitrate method4',
      8:  'Constant Bitrate (2 pass)',
      9:  'Average Bitrate (2 pass)',
      15: 'Reserved',}

   def __init__(self, frame):
      """Read the LAME info tag.

      frame should be the first frame of an mp3.
      """
      self.decode(frame)

   def _crc16(self, data, val = 0):
      """Compute a CRC-16 checksum on a data stream."""
      for c in data:
         val = self._crc16_table[ord(c) ^ (val & 0xff)] ^ (val >> 8)
      return val

   def decode(self, frame):
      """Decode the LAME info tag."""
      try: pos = frame.index("LAME")
      except: return

      # check the info tag crc.  if it's not valid, no point parsing much more.
      lamecrc = bin2dec(bytes2bin(frame[190:192]))
      if self._crc16(frame[:190]) != lamecrc:
         #TRACE_MSG('Lame tag CRC check failed')
         # read version string from the first 30 bytes, up to any
         # non-ascii chars, then strip padding chars.
         #
         # XXX (How many bytes is proper to read?  madplay reads 20, but I've
         # got files with longer version strings)
         lamever = []
         for c in frame[pos:pos + 30]:
            if ord(c) not in range(32, 127):
               break
            lamever.append(c)
         self['encoder_version'] = ''.join(lamever).rstrip('\x55')
         TRACE_MSG('Lame Encoder Version: %s' % self['encoder_version'])
         return

      TRACE_MSG('Lame info tag found at position %d' % pos)

      # Encoder short VersionString, 9 bytes
      self['encoder_version'] = lamever = frame[pos:pos + 9].rstrip()
      TRACE_MSG('Lame Encoder Version: %s' % self['encoder_version'])
      pos += 9

      # Info Tag revision + VBR method, 1 byte
      self['tag_revision'] = bin2dec(bytes2bin(frame[pos:pos + 1])[:5])
      vbr_method = bin2dec(bytes2bin(frame[pos:pos + 1])[5:])
      self['vbr_method'] = self.VBR_METHODS.get(vbr_method, 'Unknown')
      TRACE_MSG('Lame info tag version: %s' % self['tag_revision'])
      TRACE_MSG('Lame VBR method: %s' % self['vbr_method'])
      pos += 1

      # Lowpass filter value, 1 byte
      self['lowpass_filter'] = bin2dec(bytes2bin(frame[pos:pos + 1])) * 100
      TRACE_MSG('Lame Lowpass filter value: %s Hz' % self['lowpass_filter'])
      pos += 1

      # Replay Gain, 8 bytes total
      replaygain = {}

      # Peak signal amplitude, 4 bytes
      peak = bin2dec(bytes2bin(frame[pos:pos + 4])) << 5
      if peak > 0:
         peak /= float(1 << 28)
         db = 20 * log10(peak)
         replaygain['peak_amplitude'] = peak
         TRACE_MSG('Lame Peak signal amplitude: %.8f (%+.1f dB)' % (peak, db))
      pos += 4

      # Radio and Audiofile Gain, AKA track and album, 2 bytes each
      for gaintype in ['radio', 'audiofile']:
         name = bin2dec(bytes2bin(frame[pos:pos + 2])[:3])
         orig = bin2dec(bytes2bin(frame[pos:pos + 2])[3:6])
         sign = bin2dec(bytes2bin(frame[pos:pos + 2])[6:7])
         adj  = bin2dec(bytes2bin(frame[pos:pos + 2])[7:]) / 10.0
         if sign:
            adj *= -1
         # XXX Lame 3.95.1 and above use 89dB as a reference instead of 83dB
         # as defined by the Replay Gain spec.  Should this be compensated for?
         #if lamever[:4] == 'LAME' and lamevercmp(lamever[4:], '3.95') > 0:
         #   adj -= 6
         if orig:
            name = self.REPLAYGAIN_NAME.get(name, 'Unknown')
            orig = self.REPLAYGAIN_ORIGINATOR.get(orig, 'Unknown')
            replaygain[gaintype] = {'name': name, 'adjustment': adj,
                                    'originator': orig}
            TRACE_MSG('Lame %s Replay Gain: %s dB (%s)' % (name, adj, orig))
         pos += 2
      if replaygain:
         self['replaygain'] = replaygain

      # Encoding flags + ATH Type, 1 byte
      encflags = bin2dec(bytes2bin(frame[pos:pos + 1])[:4])
      self['encoding_flags'], self['nogap'] = self._parse_encflags(encflags)
      self['ath_type'] = bin2dec(bytes2bin(frame[pos:pos + 1])[4:])
      TRACE_MSG('Lame Encoding flags: %s' % ' '.join(self['encoding_flags']))
      if self['nogap']:
         TRACE_MSG('Lame No gap: %s' % ' and '.join(self['nogap']))
      TRACE_MSG('Lame ATH type: %s' % self['ath_type'])
      pos += 1

      # if ABR {specified bitrate} else {minimal bitrate}, 1 byte
      btype = 'Constant'
      if 'Average' in self['vbr_method']:
         btype = 'Target'
      elif 'Variable' in self['vbr_method']:
         btype = 'Minimum'
      # bitrate may be modified below after preset is read
      self['bitrate'] = (bin2dec(bytes2bin(frame[pos:pos + 1])), btype)
      TRACE_MSG('Lame Bitrate (%s): %s' % (btype, self['bitrate'][0]))
      pos += 1

      # Encoder delays, 3 bytes
      self['encoder_delay'] = bin2dec(bytes2bin(frame[pos:pos + 3])[:12])
      self['encoder_padding'] = bin2dec(bytes2bin(frame[pos:pos + 3])[12:])
      TRACE_MSG('Lame Encoder delay: %s samples' % self['encoder_delay'])
      TRACE_MSG('Lame Encoder padding: %s samples' % self['encoder_padding'])
      pos += 3

      # Misc, 1 byte
      sample_freq = bin2dec(bytes2bin(frame[pos:pos + 1])[:2])
      unwise_settings = bin2dec(bytes2bin(frame[pos:pos + 1])[2:3])
      stereo_mode = bin2dec(bytes2bin(frame[pos:pos + 1])[3:6])
      self['noise_shaping'] = bin2dec(bytes2bin(frame[pos:pos + 1])[6:])
      self['sample_freq'] = self.SAMPLE_FREQUENCIES.get(sample_freq, 'Unknown')
      self['unwise_settings'] = bool(unwise_settings)
      self['stereo_mode'] = self.STEREO_MODES.get(stereo_mode, 'Unknown')
      TRACE_MSG('Lame Source Sample Frequency: %s' % self['sample_freq'])
      TRACE_MSG('Lame Unwise settings used: %s' % self['unwise_settings'])
      TRACE_MSG('Lame Stereo mode: %s' % self['stereo_mode'])
      TRACE_MSG('Lame Noise Shaping: %s' % self['noise_shaping'])
      pos += 1

      # MP3 Gain, 1 byte
      sign = bytes2bin(frame[pos:pos + 1])[0]
      gain = bin2dec(bytes2bin(frame[pos:pos + 1])[1:])
      if sign:
         gain *= -1
      self['mp3_gain'] = gain
      db = gain * 1.5
      TRACE_MSG('Lame MP3 Gain: %s (%+.1f dB)' % (self['mp3_gain'], db))
      pos += 1

      # Preset and surround info, 2 bytes
      surround = bin2dec(bytes2bin(frame[pos:pos + 2])[2:5])
      preset = bin2dec(bytes2bin(frame[pos:pos + 2])[5:])
      if preset in range(8, 321):
         if self['bitrate'] >= 255:
            # the value from preset is better in this case
            self['bitrate'] = (preset, btype)
            TRACE_MSG('Lame Bitrate (%s): %s' % (btype, self['bitrate'][0]))
         if 'Average' in self['vbr_method']:
            preset = 'ABR %s' % preset
         else:
            preset = 'CBR %s' % preset
      else:
         preset = self.PRESETS.get(preset, preset)
      self['surround_info'] = self.SURROUND_INFO.get(surround, surround)
      self['preset'] = preset
      TRACE_MSG('Lame Surround Info: %s' % self['surround_info'])
      TRACE_MSG('Lame Preset: %s' % self['preset'])
      pos += 2

      # MusicLength, 4 bytes
      self['music_length'] = bin2dec(bytes2bin(frame[pos:pos + 4]))
      TRACE_MSG('Lame Music Length: %s bytes' % self['music_length'])
      pos += 4

      # MusicCRC, 2 bytes
      self['music_crc'] = bin2dec(bytes2bin(frame[pos:pos + 2]))
      TRACE_MSG('Lame Music CRC: %04X' % self['music_crc'])
      pos += 2

      # CRC-16 of Info Tag, 2 bytes
      self['infotag_crc'] = lamecrc # we read this earlier
      TRACE_MSG('Lame Info Tag CRC: %04X' % self['infotag_crc'])
      pos += 2

   def _parse_encflags(self, flags):
      """Parse encoder flags.

      Returns a tuple containing lists of encoder flags and nogap data in
      human readable format.
      """

      encoder_flags, nogap = [], []

      if not flags:
         return encoder_flags, nogap

      if flags & self.ENCODER_FLAGS['NSPSYTUNE']:
         encoder_flags.append('--nspsytune')
      if flags & self.ENCODER_FLAGS['NSSAFEJOINT']:
         encoder_flags.append('--nssafejoint')

      NEXT = self.ENCODER_FLAGS['NOGAP_NEXT']
      PREV = self.ENCODER_FLAGS['NOGAP_PREV']
      if flags & (NEXT | PREV):
         encoder_flags.append('--nogap')
         if flags & PREV:
            nogap.append('before')
         if flags & NEXT:
            nogap.append('after')
      return encoder_flags, nogap

def lamevercmp(x, y):
   """Compare LAME version strings.

   alpha and beta versions are considered older.
   versions with sub minor parts or end with 'r' are considered newer.

   Return negative if x<y, zero if x==y, positive if x>y.
   """

   x = x.ljust(5)
   y = y.ljust(5)
   if x[:5] == y[:5]: return 0
   ret = cmp(x[:4], y[:4])
   if ret: return ret
   xmaj, xmin = x.split('.')[:2]
   ymaj, ymin = y.split('.')[:2]
   minparts = ['.']
   # lame 3.96.1 added the use of r in the very short version for post releases
   if (xmaj == '3' and xmin >= '96') or (ymaj == '3' and ymin >= '96'):
      minparts.append('r')
   if x[4] in minparts: return 1
   if y[4] in minparts: return -1
   if x[4] == ' ': return 1
   if y[4] == ' ': return -1
   return cmp(x[4], y[4])