Mac- oder Unix-kompatibles Dienstprogramm zum Berechnen und Vergleichen von LAME MusicCRC in MP3s?

Hier eine Bash-Shell-Funktion lameCRC(), die LAME musicCRC und CRC-16 des Xing / Info-LAME-Header-Frames (wie in den Spezifikationen für Mp3-Info-Tags Version 1 - Entwurf 0 angegeben ) mithilfe des Apple- afinfoBefehls und des crcBefehlszeilentools von Hampa berechnet Hug, http://www.hampa.ch/misc-utils/index.html .

Wenn der afinfoBefehl von Apple nicht verfügbar ist, ddwird verwendet (was jedoch zu einem Geschwindigkeitsüberfall führt).

(Hinweis: Ich habe bewusst auf die internen String-Funktionen von Bash verzichtet, um die Portabilität zu erleichtern).

lameCRC() { # Bash shell function  # lameCRC() uses the crc command line tool from http://www.hampa.ch/misc-utils/index.html. # lameCRC() is partly inspired by the output of Apple's afinfo command and  # the C source code of Audio-Scan-0.93 and MP3-Cut-Gapless-0.03 by Andy Grundman: # https://metacpan.org/author/AGRUNDMA # Audio-Scan-0.93/src/mp3.c (GNU General Public License Version 2, June 1991 or later) # Audio-Scan-0.93/include/mp3.h ( ditto ) # MP3-Cut-Gapless-0.03/src/mp3cut.c ( ditto )  # usage: lameCRC lame.mp3  # Basic information:  # Mp3 Info Tag rev 1 specifications, http://gabriel.mp3-tech.org/mp3infotag.html # LAME info header zone A has a length of 120 bytes (or 240 chars in xxd hex output). # The "LAMEx." string is followed by 30 bytes (or 60 chars in xxd hex output) according to the  # "Suggested Info Tag extension fields + layout" in the Mp3 Info Tag rev 1 specifications.  local n n1 n2 lines plus crcs hexchar lame_start_idx xinginfo_start_idx PATH  PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin  [[ ! -x '/usr/local/bin/crc' ]] &&  { printf '%s\n' 'No crc command line tool in /usr/local/bin!' 'See: http://www.hampa.ch/misc-utils/index.html' 1>&2; }  # get Xing|Info|LAME strings and their offsets in binary file lines="$(strings -a -n 4 -t d "$1" | grep -E --line-buffered 'Xing|Info|LAME.\.' | head -n 2)"   [[ $(echo "$lines" | grep -E -c 'Xing|Info') -ne 1 ]] || [[ $(echo "$lines" | grep -E -c 'LAME[^ ]') -ne 1 ]] && { echo 'No Xing|Info string or correct LAME encoder version string (e.g. LAME3.98r) found!' 1>&2;  echo "$lines" 1>&2; return 1;  }  # get offset index numbers of Xing|Info|LAME strings lame_start_idx="$(printf '%s' "$lines" | awk '/LAME/' )" xinginfo_start_idx="$(printf '%s' "$lines" | awk '/Xing|Info/' )"  # get possible offset of LAME string in output of strings command # LAME version string should consist of 9 chars, but may have a prefix in output of strings command # example: 9LAME3.98r instead of LAME3.98r # example: 7LAME3.88 (beta) instead of LAME3.88 (beta) #plus="$(printf '%s' "$lines" | sed -n 's/^[^ ]*[ ][ ]*\([^ ]*\)LAME[^ ]\.*/\1/p' | tr -d '\n' | wc -c)" # use [^ ]\ ? plus="$(printf '%s' "$lines" | sed -n 's/^[^ ]*[ ][ ]*\([^ ]*\)LAME.*/\1/p' | tr -d '\n' | wc -c)"  lame_start_idx=$(( $lame_start_idx + $plus ))  [[ $(( $lame_start_idx - $xinginfo_start_idx )) -ne 120 ]] &&  { echo 'No 120 bytes between Xing / Info and LAME string. Exiting ...' 1>&2; return 1; }  # get entire LAME info tag #dd if="$1" bs=1 skip="$lame_start_idx" count=36 2>/dev/null | LC_ALL=C od -A n -cv; return 0  # get bytes $BC-$BD (MusicCRC) and bytes $BE-$BF (CRC-16 of Info Tag) (as described in http://gabriel.mp3-tech.org/mp3infotag.html) crcs="$(dd if="$1" bs=1 skip="$(( $lame_start_idx + 32 ))" count=4 2>/dev/null | xxd -p | tr -d '\n')"  [[ -z "$crcs" ]] && { echo 'No LAME musicCRC and CRC-16 of Info Tag found!' 1>&2; return 1; }  lameMusicLengthPlusCRCs="$(dd if="$1" bs=1 skip=$(( $lame_start_idx + 28 )) count=8 2>/dev/null | xxd -p | tr -d '\n')" lameMusicLength="$(echo "$lameMusicLengthPlusCRCs" | cut -b 1-8 )" lameMusicCRC1="$(echo "$lameMusicLengthPlusCRCs" | cut -b 9-10 )" # cf. http://gabriel.mp3-tech.org/mp3infotag#musiccrc lameMusicCRC2="$(echo "$lameMusicLengthPlusCRCs" | cut -b 11-12 )" lameInfoTagCRC16="$(echo "$lameMusicLengthPlusCRCs" | cut -b 13-16 )"  # LAME MusicLength consists of:  # [LAME Tag frame][complete mp3 music data] lameMusicLengthByteSize=$(printf '%d' "0x$")  [[ $lameMusicLengthByteSize -le 0 ]] && { echo 'lameMusicLengthByteSize <= 0. Exiting ...' 1>&2; return 1; }   if [[ -x '/usr/bin/sw_vers' ]] && [[ "$(/usr/bin/sw_vers -productName)" == "Mac OS X" ]] && [[ -x '/usr/bin/afinfo' ]]; then  # get audio_bytes, i. e. [complete mp3 music data] - [LAME Tag frame]  #id3v2 --delete-all "$1" 1>/dev/null # for testing purposes; edits file in-place! # afinfo seems to be only available on Mac OS X  # afinfo alternative: Perl module Audio-Scan-0.93 by Andy Grundman  # perl -e 'use Audio::Scan; my $offset = Audio::Scan->find_frame($ARGV[1],0); print "$offset\n";' _ file.mp3 audioinfo="$(afinfo "$1")"  audio_bytes="$(echo "$audioinfo" | awk -F" " '/audio bytes:/' )" audio_data_file_offset="$(echo "$audioinfo" | awk -F" " '/audio data file offset:/')" xingInfoLameTagFrameSize=$(( lameMusicLengthByteSize - audio_bytes ))  [[ $audio_bytes -le 0 ]] && { echo 'audio_bytes <= 0. Exiting ...' 1>&2; return 1; }  # 0..xingInfoLameTagFrameOffset (match first 0xff byte in mp3 file) n=0 hexchar="" until [[ "$hexchar" == 'ff' ]]; do hexchar="$(dd if="$1" bs=1 skip=$n count=1 2>/dev/null | xxd -p)" n=$(( n + 1)) done xingInfoLameTagFrameOffset=$(( n - 1 ))  else # dd speed bump  # get xingInfoLameTagFrameSize # for mp3 magic numbers (\xFF\xFB) see:  # http://www.digitalpreservation.gov/formats/fdd/fdd000105.shtml  # n1 # count bytes from: 0xff...<--...$xinginfo_start_idx hexchar="" n=$xinginfo_start_idx until [[ "$hexchar" == 'ff' ]]; do n=$(( n - 1)) hexchar="$(dd if="$1" bs=1 skip=$n count=1 2>/dev/null | xxd -p)" done xingInfoLameTagFrameOffset=$n n1=$(( xinginfo_start_idx - n ))  # n2 # count bytes from: $xinginfo_start_idx+120+36...-->...0xff hexchar="" n=$((xinginfo_start_idx + 120 + 36)) until [[ "$hexchar" == 'ff' ]]; do hexchar="$(dd if="$1" bs=1 skip=$n count=1 2>/dev/null | xxd -p)" n=$(( n + 1)) done n2=$(( n - xinginfo_start_idx - 120 - 36 - 1 )) # - 1 because the trailing 0xff got counted by $n  xingInfoLameTagFrameSize=$(( $n1 + $n2 + 120 + 36 )) audio_data_file_offset=$((xingInfoLameTagFrameOffset + xingInfoLameTagFrameSize))  # get audio_bytes, i. e. [complete mp3 music data] - [LAME Tag frame] audio_bytes=$( printf "%s\n" "scale = 0; $ - $" | bc )  fi  old_lameInfoTagCRC16="$lameInfoTagCRC16" new_lameInfoTagCRC16="$(head -c $(( xingInfoLameTagFrameOffset + xingInfoLameTagFrameSize )) "$1" |  tail -c $ | head -c 190 | crc -R -r -g crc16)"  old_lameMusicCRC16="$$" new_lameMusicCRC16="$(head -c $(( $ + $ )) "$1" |  tail -c $ | crc -R -r -g crc16)"  echo printf '%s\n' "old_lameInfoTagCRC16: $" "new_lameInfoTagCRC16: $" echo printf '%s\n' "old_lameMusicCRC16: $" "new_lameMusicCRC16: $" echo  return 0 } 

There seems to be a C port of LameTag_Source_0.4.1/CRC16.pas called mp3_check-1.98/crctest.c (which is a command line tool).

Here's a hacked version of mp3_check-1.98/crctest.c that that will calculate the CRC16 checksum of a given mp3 file.

/* modified version of source code taken from: mp3_check-1.98/crctest.c, http://sourceforge.net/projects/mp3check/ NOTE: compare mp3_check-1.98/crctest.c with LameTag_Source_0.4.1/CRC16.pas from http://phwip.wordpress.com/home/audio/ See also: mp3check - check mp3 files for integrity, http://jo.ath.cx/soft/mp3check/ gcc -Wall -Wextra -03 -o crctest crctest.c ./crctest *.mp3 printf '%d\n' $(./crctest *.mp3) */ #include <stdio.h> #include <stdlib.h> int crcbuf(crc, len, buf) register int crc; /* running CRC value */ register unsigned long len; register char *buf; { static short crc_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 }; register unsigned long i; for (i=0; i<len; i++) crc = ((crc >> 8) & 0xff) ^ crc_table[(crc ^ *buf++) & 0xff]; return (crc); } int main (int argc, char * argv []) { if (argc != 2) return(1); int crc = 0; int newcrc = 0; // cf. http://www.linuxquestions.org/questions/programming-9/c-howto-read-binary-file-into-buffer-172985/ char *name = argv[1]; FILE *file; char *buffer; unsigned long fileLen; //Open file file = fopen(name, "rb"); if (!file) { fprintf(stderr, "Unable to open file %s", name); return(1); } //Get file length fseek(file, 0, SEEK_END); fileLen=ftell(file); fseek(file, 0, SEEK_SET); //Allocate memory buffer=(char *)malloc(fileLen+1); if (!buffer) { fprintf(stderr, "Memory error!"); fclose(file); return(1); } //Read file contents into buffer fread(buffer, fileLen, 1, file); fclose(file); newcrc = crcbuf(crc, fileLen, buffer); printf("0x%x\n", newcrc); free(buffer); return(0); } 

I'll answer my own question here:

In trying to research this, i stumbled across a Python script for mutagen, QuodLibet's audio meta-data library. The script is designed to read LAME's Info Tag, and although it does not deal with either of the CRC fields specifically, i was able to create something that does based off of its example. After a few hours of messing with things (i'm a terrible programmer and know absolutely nothing about Python) i finally managed to write something that, although featureless and slow, does return the original CRCs and compute the new ones. It's still a little buggy, but on my own library it turned out to be at least 90% accurate, so i'll 'release' it i guess. It's called mp3crc and is available on GitHub:

https://github.com/ohkine/mp3crc

The script should run on UNIX and Windows, although there is currently a Windows-only Unicode issue that needs fixed. It also requires crcmod and mutagen to be installed (i include them in the repository but you can install them however).

As mentioned i'm not a very good programmer, so i apologise in advance for how embarrassing the code probably is. But it mostly works :)