Detecting valid mp3 or not

[Blobby]

Does anyone know if there is a way to detect if an mp3 file is a genuine mp3 file instead of a .txt file or something renamed to .mp3? Thanks for any feedback

[RobIII]

I doubt if there is a safe way. An MP3 file is just raw data wich doesn't really have a header or something. So it's going to get hard, i can tell you that much...

I found some info, but again, no real verification. As you can see, the header is just a bunch of bits. They can be any value. If it were "MP3" and then the rest of the bits it would've been easier.

Mpeg 1.0/2.0 LayersI, II and III header and trailer formats
-----------------------------------------------------------
* HEADER
 
 
bits name              comments
--------------------------------------------------
11   sync              0xFFF
2    version           1=mpeg1.0, 0=mpeg2.0
2    lay               4-lay = layerI, II or III
1    error protection  0=yes, 1=no
4    bitrate_index     see table below
2    sampling_freq     see table below
1    padding
1    extension         see table below
2    mode              see table below
2    mode_ext          used with "joint stereo" mode
1    copyright         0=no 1=yes
1    original          0=no 1=yes
2    emphasis          see table below
--------------------------------------------------
 
- bitrate_index
 
. mpeg1.0
 
            1  2  3   4   5   6   7   8   9  10  11  12  13  14
layer1     32 64 96 128 160 192 224 256 288 320 352 384 416 448
layer2     32 48 56  64  80  96 112 128 160 192 224 256 320 384
layer3     32 40 48  56  64  80  96 112 128 160 192 224 256 320
 
. mpeg2.0
 
            1  2  3   4   5   6   7   8   9  10  11  12  13  14
layer1     32 48 56  64  80  96 112 128 144 160 176 192 224 256
layer2      8 16 24  32  40  48  56  64  80  96 112 128 144 160
layer3      8 16 24  32  40  48  56  64  80  96 112 128 144 160
 
 
- sampling_freq
 
. mpeg1.0
 
    0     1     2     
 
44100 48000 32000 
 
. mpeg2.0
 
    0     1     2     
 
22050 24000 16000 
 
 
- mode:
 
0 "stereo"
1 "joint stereo"
2 "dual channel"
3 "single channel"
 
 
- mode extension:
 
0      MPG_MD_LR_LR
1      MPG_MD_LR_I
2      MPG_MD_MS_LR 
3      MPG_MD_MS_I
 
jsbound :
 
   mode_ext     0  1   2   3
layer
1               4  8  12  16
2               4  8  12  16
3               0  4   8  16
 
 
- emphasis:
 
0 "none"
1 "50/15 microsecs"
2 "reserved"            must not be used !
3 "CCITT J 17"
 
 
 
 
* TRAILER
 
at end of file - 128 bytes
 
offset  type  len   name
--------------------------------------------
0       char  3                   "TAG"
3       char  30    title
33      char  30    artist
63      char  30    album
93      char  4     year
97      char  30    comments
127     byte  1     genre
--------------------------------------------
 
- genre :
 
 0    "Blues"
 1    "Classic Rock"
 2    "Country"
 3    "Dance"
 4    "Disco"
 5    "Funk"
 6    "Grunge"
 7    "Hip-Hop"
 8    "Jazz"
 9    "Metal"
10    "New Age"
11    "Oldies"
12    "Other"
13    "Pop"
14    "R&B"
15    "Rap"
16    "Reggae"
17    "Rock"
18    "Techno"
19    "Industrial"
20    "Alternative"
21    "Ska"
22    "Death Metal"
23    "Pranks"
24    "Soundtrack"
25    "Euro-Techno"
26    "Ambient"
27    "Trip-Hop"
28    "Vocal"
29    "Jazz+Funk"
30    "Fusion"
31    "Trance"
32    "Classical"
33    "Instrumental"
34    "Acid"
35    "House"
36    "Game"
37    "Sound Clip"
38    "Gospel"
39    "Noise"
40    "AlternRock"
41    "Bass"
42    "Soul"
43    "Punk"
44    "Space"
45    "Meditative"
46    "Instrumental Pop"
47    "Instrumental Rock"
48    "Ethnic"
49    "Gothic"
50    "Darkwave"
51    "Techno-Industrial"
52    "Electronic"
53    "Pop-Folk"
54    "Eurodance"
55    "Dream"
56    "Southern Rock"
57    "Comedy"
58    "Cult"
59    "Gangsta"
60    "Top 40"
61    "Christian Rap"
62    "Pop/Funk"
63    "Jungle"
64    "Native American"
65    "Cabaret"
66    "New Wave"
67    "Psychadelic"
68    "Rave"
69    "Showtunes"
70    "Trailer"
71    "Lo-Fi"
72    "Tribal"
73    "Acid Punk"
74    "Acid Jazz"
75    "Polka"
76    "Retro"
77    "Musical"
78    "Rock & Roll"
79    "Hard Rock"
80    "Unknown"
 
 
 
- frame length :
 
. mpeg1.0
 
layer1 :
 (48000*bitrate)/sampling_freq + padding
layer2&3:
 (144000*bitrate)/sampling_freq + padding
 
. mpeg2.0
 
layer1 :
 (24000*bitrate)/sampling_freq + padding
layer2&3 :
 (72000*bitrate)/sampling_freq + padding

[Michael_Kamen]

I think you need to find information about the header of MP3 files.

[Blobby]

Cheers Guys. Thanks RobIII, thats what i figured. I didnt know if some clever sod had devised a way of detecting it. trouble is, if i rename a text file as .mp3 my app will allow it to play but because it isnt a real mp3 file, winamp just sits there in limbo and crashes the whole app! I guess all i can do now is do a test after 3 seconds or so and if its 'Playing' but the track position is still at zero i can stop the track and report an error. Thanks for your time tho!