how to fetch the details of the audio file in iPhone

Question

I made the custom player by using AVAudioPlayer. Now, I want to fetch the details of the audio file such as artist name,album name,etc which is added in the resource folder.

MPMusicPlayer provides the API for fetching the details but its using iPod library and its not taking the resource from sandbox of application. So, MPMusicPlayer is not going to work in that scenario.

So, how can we fetch the details of audio file in iPhone.

Answer 1

You can get this information through the AudioToolbox.framework. The AudioToolbox.framework is a C API, so I wrote an Objective-C wrapper for it:

ID3Tag .h:

@interface ID3Tag : NSObject <NSCoding> {
    NSString* title_;
    NSString* album_;
    NSString* artist_;
    NSNumber* trackNumber_;
    NSNumber* totalTracks_;
    NSString* genre_;
    NSString* year_;
    NSNumber* approxDuration_;
    NSString* composer_;
    NSString* tempo_;
    NSString* keySignature_;
    NSString* timeSignature_;
    NSString* lyricist_;
    NSString* recordedDate_;
    NSString* comments_;
    NSString* copyright_;
    NSString* sourceEncoder_;
    NSString* encodingApplication_;
    NSString* bitRate_;
    NSStream* sourceBitRate_;
    NSString* channelLayout_;
    NSString* isrc_;
    NSString* subtitle_;  
}

@property (nonatomic, retain) NSString *title;
@property (nonatomic, retain) NSString *album;
@property (nonatomic, retain) NSString *artist;
@property (nonatomic, retain) NSNumber *trackNumber;
@property (nonatomic, retain) NSNumber *totalTracks;
@property (nonatomic, retain) NSString *genre;
@property (nonatomic, retain) NSString *year;
@property (nonatomic, retain) NSNumber *approxDuration;
@property (nonatomic, retain) NSString *composer;
@property (nonatomic, retain) NSString *tempo;
@property (nonatomic, retain) NSString *keySignature;
@property (nonatomic, retain) NSString *timeSignature;
@property (nonatomic, retain) NSString *lyricist;
@property (nonatomic, retain) NSString *recordedDate;
@property (nonatomic, retain) NSString *comments;
@property (nonatomic, retain) NSString *copyright;
@property (nonatomic, retain) NSString *sourceEncoder;
@property (nonatomic, retain) NSString *encodingApplication;
@property (nonatomic, retain) NSString *bitRate;
@property (nonatomic, retain) NSStream *sourceBitRate;
@property (nonatomic, retain) NSString *channelLayout;
@property (nonatomic, retain) NSString *isrc;
@property (nonatomic, retain) NSString *subtitle;

@end

ID3TagParser.h

#import <Foundation/Foundation.h>
#import "ID3Tag.h"

@interface ID3Parser : NSObject {

}

- (ID3Tag*) parseAudioFileForID3Tag:(NSURL*) url;

@end

ID3TagParser.m

#import "ID3Parser.h"
#import <AudioToolbox/AudioToolbox.h>

@implementation ID3Parser

- (ID3Tag*) parseAudioFileForID3Tag:(NSURL*) url {
    if (url == nil) {
        return nil;
    }

    AudioFileID fileID  = nil;
    OSStatus err = noErr;

    err = AudioFileOpenURL( (CFURLRef) url, kAudioFileReadPermission, 0, &fileID );
    if( err != noErr ) {
        NSLog( @"AudioFileOpenURL failed" );
        return nil;
    } else {
        UInt32 id3DataSize = 0;
        char* rawID3Tag = NULL;

        //  Reads in the raw ID3 tag info
        err = AudioFileGetPropertyInfo(fileID, kAudioFilePropertyID3Tag, &id3DataSize, NULL);
        if(err != noErr) {
            return nil;
        }

        //  Allocate the raw tag data
        rawID3Tag = (char *) malloc(id3DataSize);

        if(rawID3Tag == NULL) {
            return nil;
        }

        err = AudioFileGetProperty(fileID, kAudioFilePropertyID3Tag, &id3DataSize, rawID3Tag);
        if(err != noErr) {
            return nil;
        }

        UInt32 id3TagSize = 0;
        UInt32 id3TagSizeLength = 0;
        err = AudioFormatGetProperty(kAudioFormatProperty_ID3TagSize, id3DataSize, rawID3Tag, &id3TagSizeLength, &id3TagSize);

        if(err != noErr) {
            switch(err) {
                case kAudioFormatUnspecifiedError:
                    NSLog(@"err: audio format unspecified error");
                    return nil;
                case kAudioFormatUnsupportedPropertyError:
                    NSLog(@"err: audio format unsupported property error");
                    return nil;
                case kAudioFormatBadPropertySizeError:
                    NSLog(@"err: audio format bad property size error"); 
                    return nil;
                case kAudioFormatBadSpecifierSizeError:
                    NSLog(@"err: audio format bad specifier size error"); 
                    return nil;
                case kAudioFormatUnsupportedDataFormatError:
                    NSLog(@"err: audio format unsupported data format error"); 
                    return nil;
                case kAudioFormatUnknownFormatError:
                    NSLog(@"err: audio format unknown format error");
                    return nil;
                default:
                    NSLog(@"err: some other audio format error"); 
                    return nil;
            }
        }

        CFDictionaryRef piDict = nil;
        UInt32 piDataSize = sizeof(piDict);

        //  Populates a CFDictionary with the ID3 tag properties
        err = AudioFileGetProperty(fileID, kAudioFilePropertyInfoDictionary, &piDataSize, &piDict);
        if(err != noErr) {
            NSLog(@"AudioFileGetProperty failed for property info dictionary");
            return nil;
        }

        //  Toll free bridge the CFDictionary so that we can interact with it via objc
        NSDictionary* nsDict = (NSDictionary*)piDict;

        ID3Tag* tag = [[[ID3Tag alloc] init] autorelease];

        tag.album = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Album]];
        tag.approxDuration = [NSNumber numberWithInt:[[nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_ApproximateDurationInSeconds]] intValue]];
        tag.artist = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Artist]];
        tag.bitRate = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_NominalBitRate]];
        tag.channelLayout = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_ChannelLayout]];
        tag.comments = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Comments]];
        tag.composer = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Composer]];
        tag.copyright = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Copyright]];
        tag.encodingApplication = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_EncodingApplication]];
        tag.genre = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Genre]];
        tag.isrc = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_ISRC]];
        tag.keySignature = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_KeySignature]];
        tag.lyricist = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Lyricist]];
        tag.recordedDate = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_RecordedDate]];
        tag.sourceBitRate = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_SourceBitDepth]];
        tag.sourceEncoder = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_SourceEncoder]];
        tag.subtitle = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_SubTitle]];
        tag.tempo = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Tempo]];
        tag.timeSignature = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_TimeSignature]];
        tag.title = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Title]];
        tag.year = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_Year]];

        /*  
         *  We're going to parse tracks differently so that we can perform queries on the data. This means we need to look
         *  for a '/' so that we can seperate out the track from the total tracks on the source compilation (if it's there).
         */
        NSString* tracks = [nsDict objectForKey:[NSString stringWithUTF8String: kAFInfoDictionary_TrackNumber]];

        int slashLocation = [tracks rangeOfString:@"/"].location;

        if (slashLocation == NSNotFound) {
            tag.trackNumber = [NSNumber numberWithInt:[tracks intValue]];
        } else {
            tag.trackNumber = [NSNumber numberWithInt:[[tracks substringToIndex:slashLocation] intValue]];
            tag.totalTracks = [NSNumber numberWithInt:[[tracks substringFromIndex:(slashLocation+1 < [tracks length] ? slashLocation+1 : 0 )] intValue]];
        }

        //  ALWAYS CLEAN UP!
        CFRelease(piDict);
        nsDict = nil;
        free(rawID3Tag);

        return tag;
    }
}

@end

Answer 2

I see that the tag-reading code Wayne posts is being copy-pasted too much. If you use kAudioFilePropertyInfoDictionary, you don't need id3DataSize, don't need to read raw ID3Tag data and id3TagSizeLength id3TagSize are not used also. Just open the file and read the tag:

- (NSDictionary *)id3TagsForURL:(NSURL *)resourceUrl
{
    AudioFileID fileID;
    OSStatus result = AudioFileOpenURL((CFURLRef)resourceUrl, kAudioFileReadPermission, 0, &fileID);

    if (result != noErr) {
        NSLog(@"Error reading tags: %li", result);
        return nil;
    }

    CFDictionaryRef piDict = nil;
    UInt32 piDataSize = sizeof(piDict);

    result = AudioFileGetProperty(fileID, kAudioFilePropertyInfoDictionary, &piDataSize, &piDict);
    if (result != noErr)
        NSLog(@"Error reading tags. AudioFileGetProperty failed");

    AudioFileClose(fileID);

    NSDictionary *tagsDictionary = [NSDictionary dictionaryWithDictionary:(NSDictionary*)piDict];
    CFRelease(piDict);

    return tagsDictionary;
}

Dicionary keys are defined in AudioFile.h, starting with kAFInfoDictionary.

However, there is another tag-reading key, which will return different results (with other keys):

- (NSDictionary *)id3TagsForURL:(NSURL *)resourceUrl
{
    AudioFileID fileID;
    OSStatus result = AudioFileOpenURL((CFURLRef)resourceUrl, kAudioFileReadPermission, 0, &fileID);

    if (result != noErr) {
        return nil;
    }

    //read raw ID3Tag size
    UInt32 id3DataSize = 0;
    char *rawID3Tag = NULL;
    result = AudioFileGetPropertyInfo(fileID, kAudioFilePropertyID3Tag, &id3DataSize, NULL);
    if (result != noErr) {
        AudioFileClose(fileID);
        return nil;
    }

    rawID3Tag = (char *)malloc(id3DataSize);

    //read raw ID3Tag
    result = AudioFileGetProperty(fileID, kAudioFilePropertyID3Tag, &id3DataSize, rawID3Tag);
    if (result != noErr) {
        free(rawID3Tag);
        AudioFileClose(fileID);
        return nil;
    }

    CFDictionaryRef piDict = nil;
    UInt32 piDataSize = sizeof(piDict);

    //this key returns some other dictionary, which works also in iPod library
    result = AudioFormatGetProperty(kAudioFormatProperty_ID3TagToDictionary, id3DataSize, rawID3Tag, &piDataSize, &piDict);
    if (result != noErr) {
        return nil;
    }

    free(rawID3Tag);
    AudioFileClose(fileID);

    NSDictionary *tagsDictionary = [NSDictionary dictionaryWithDictionary:(NSDictionary*)piDict];
    CFRelease(piDict);

    return tagsDictionary;
}