CocoaDev

I’m going to help a friend rip his entire CD collection (300+) into mp3 file format. The only problem is he has dialup and and a single shared phone line. I have already downloaded freeDB’s database (really large if you leave all entries in uncompressed individual files), so most of the track info will be on a local HD. My only problem is getting cd-discid or discid to work on Panther. I only need the 32 bit hex id to access the database. Has anyone gotten either of these command line tools to work in Panther? Does anyone know of a way to get iTunes to reveal the “disc id” of a mounted CD?

BTW, when I try to use cd-discid by passing “/dev/disk2” as the only argument I get the following error:

cd-discid: /dev/disk2: DKIOCCDREADTRACKINFO: Input/output error

ok, here’s what I figured out. Just give UmDiscIDAtPath the path to the table of contents plist found in the directory of the mounted audio cd volume (the file is named .TOC.plist). Hopefully OS X will always provide this property list. Now all I have to do is parse 1 GB of cddb entries!! –zootbobbalu

extern unsigned int UmDiscIDAtPath(NSString *path);

static int UmCDDBSum(int n) { int ret = 0; while (n > 0) {ret += (n % 10); n /= 10;} return (ret); }

unsigned int UmDiscIDAtPath(NSString *path) {

if (!path) return nil;
NSDictionary *plist = [NSDictionary dictionaryWithContentsOfFile:path];
NSArray *sessions = [plist objectForKey:@"Sessions"];
int i, sum = 0, leadInBlock, cnt;
if ([sessions count]) {
    NSDictionary *session1 = [sessions objectAtIndex:0];
    NSArray *tracks = [session1 objectForKey:@"Track Array"];
    cnt = [tracks count];
    for (i = 0; i < cnt; i++) {
        int block = [tracks objectAtIndex:i] objectForKey:@"Start Block"] intValue];
        sum += [[UmCDDBSum(block / 75);
        if (!i) leadInBlock = block;
    }
    return ((sum % 0xff) << 24 | 
            (session1 objectForKey:@"Leadout Block"] intValue] - leadInBlock) / 75 << 8 | cnt);
}
return nil; }

I just started looking at [[MusicBrainz ( see http://www.musicbrainz.org/ ) to get CD metadata, links to Amazon, and so forth. The starting point is to generate a discid from the .TOC.plist file, which is read when you insert the CD. Here’s my version:

-(NSString* )TOCPath { // TODO: return the path to the .TOC.plist file from this method }

-(NSDictionary* )TOC { return [NSDictionary dictionaryWithContentsOfFile:[self TOCPath]]; }

-(NSDictionary* )sessionWithIndex:(unsigned)theSession { NSArray* theArray = self TOC] objectForKey:@”Sessions”]; if([theArray isKindOfClass:[[[NSArray class]]==NO) return nil; if(theSession >= [theArray count]) return nil; return [theArray objectAtIndex:theSession]; }

-(NSString* )discID { // see: http://wiki.musicbrainz.org/DiscIDCalculation // always use the first session for this - may not be right thing to do??? NSDictionary* theSession = [self sessionWithIndex:0];

// write header NSMutableString* theString = [NSMutableString stringWithFormat:@”%02X%02X%08X”, theSession objectForKey:@”First Track”] unsignedIntValue], [[theSession objectForKey:@”Last Track”] unsignedIntValue], [[theSession objectForKey:@”Leadout Block”] unsignedIntValue;

// write tracks NSArray* theTracks = [theSession objectForKey:@”Track Array”]; for(unsigned theTrack = 0; theTrack < 99; theTrack++) { if(theTrack < [theTracks count]) { [theString appendFormat:@”%08X”,[theTracks objectAtIndex:theTrack] objectForKey:@”Start Block”] unsignedIntValue; } else { [theString appendString:@”00000000”]; } }

// compute SHA1 digest NSData* theDigest = theString dataUsingEncoding:NSUTF8StringEncoding] sha1Digest]; // convert to base 64 [[NSMutableString* theBase64 = [NSMutableString stringWithString:[theDigest encodeBase64WithNewlines:NO]]; // to convert to MusicBrainz format, convert some non-URI characters… // replace ‘=’ with ‘-‘, ‘+’ with ‘.’ and ‘/’ with ‘’ [theBase64 replaceOccurrencesOfString:@”=” withString:@”-“ options:0 range:NSMakeRange(0,[theBase64 length])]; [theBase64 replaceOccurrencesOfString:@”+” withString:@”.” options:0 range:NSMakeRange(0,[theBase64 length])]; [theBase64 replaceOccurrencesOfString:@”/” withString:@”” options:0 range:NSMakeRange(0,[theBase64 length])]; // return the discid return theBase64; }

You’ll need the NSData additions from the BaseSixtyFour page on this wiki.

• DavidThorpe