Failed to read audio data from audio file (-4)

[jglezmaestro]

Crash on iPhone 4 iOS 6 when try to getWaveformDataWithCompletionBlock from an ipod-library URL-scheme URL. On iPhone 5 iOS 7.1 all works fine.

[syedhali]

Please see my response to issue #12. You can still access iPod songs as EZAudioFile, but you first have to use the AVAssetExportSession to move the audio to a valid url that EZAudioFile can use.

//
// Creates an EZAudioFile from an MPMediaItem representing a song coming from
// an iOS device's iPod library. Since an MPMediaItem's URL is always prefixed
// with an ipod:// path we must use the AVAssetExportSession to first export
// the song to a file path that the EZAudioFile can actually find in the app's bundle.
//
- (void)openMediaItem:(MPMediaItem *)item
           completion:(void(^)(EZAudioFile *audioFile, NSError *error))completion
{
    NSURL *url = [item valueForProperty:MPMediaItemPropertyAssetURL];
    NSString *title = [item valueForProperty:MPMediaItemPropertyTitle];
    if (url)
    {
        //
        // Create an AVAudioExportSession to export the MPMediaItem to a non-iPod
        // file path url we can actually use for an EZAudioFile
        //
        AVURLAsset *asset = [AVURLAsset assetWithURL:url];
        AVAssetExportSession *exporter = [AVAssetExportSession exportSessionWithAsset:asset
                                                                           presetName:AVAssetExportPresetAppleM4A];
        exporter.outputFileType = @"com.apple.m4a-audio";
        NSString *exportURLPath = [[self applicationDocumentsDirectory] stringByAppendingFormat:@"/%@.m4a", title];
        NSURL *exportURL = [NSURL fileURLWithPath:exportURLPath];
        exporter.outputURL = exportURL;

        //
        // Delete any existing path in the bundle if one already exists
        //
        NSFileManager *fileManager = [NSFileManager defaultManager];
        if ([fileManager fileExistsAtPath:exportURLPath])
        {
            NSError *error;
            [fileManager removeItemAtPath:exportURLPath error:&error];
            if (error)
            {
                NSLog(@"error deleting file: %@", error.localizedDescription);
            }
        }

        //
        // Export the audio data using the AVAudioExportSession to the
        // exportURL in the application bundle
        //
        [exporter exportAsynchronouslyWithCompletionHandler:^{
            AVAssetExportSessionStatus status = [exporter status];
            switch (status)
            {
                case AVAssetExportSessionStatusCompleted:
                {
                    EZAudioFile *file = [EZAudioFile audioFileWithURL:exportURL];
                    completion(file ,nil);
                    break;
                }
                case AVAssetExportSessionStatusFailed:
                {
                    completion(nil, exporter.error);
                    break;
                }
                default: 
                {
                    NSLog(@"Exporter status not fialed or complete: %ld", status);
                    break;
                }
            }
        }];
    }
    else
    {
        NSError *error = [NSError errorWithDomain:@"com.myapp.sha"
                                             code:404
                                         userInfo:@{ NSLocalizedDescriptionKey : @"Media item's URL not found" }];
        completion(nil, error);
    }
}