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copied!<p>Of course you can access the data of a <code>MPMediaItem</code>. It's not crystal clear at once but it works. Here's how:</p> <ul> <li>Get the media item's URL from it's <code>MPMediaItemPropertyAssetURL</code> property</li> <li>Initialize an <code>AVURLAsset</code> with this URL</li> <li>Initialize an <code>AVAssetReader</code> with this asset</li> <li>Fetch the <code>AVAssetTrack</code> you want to read from the <code>AVURLAsset</code></li> <li>Create an <code>AVAssetReaderTrackOutput</code> with this track</li> <li>Add this output to the <code>AVAssetReader</code> created before and <code>-startReading</code></li> <li>Fetch all data with <code>AVAssetReaderTrackOutput</code>'s <code>-copyNextSampleBuffer</code></li> <li>PROFIT!</li> </ul> <p>Here is some sample code from a project of mine (this is not a code jewel of mine, wrote it some time back in my coding dark ages):</p> <pre><code>typedef enum { kEDSupportedMediaTypeAAC = 'aac ', kEDSupportedMediaTypeMP3 = '.mp3' } EDSupportedMediaType; - (EDLibraryAssetReaderStatus)prepareAsset { // Get the AVURLAsset AVURLAsset *uasset = [m_asset URLAsset]; // Check for DRM protected content if (uasset.hasProtectedContent) { return kEDLibraryAssetReader_TrackIsDRMProtected; } if ([uasset tracks] == 0) { DDLogError(@"no asset tracks found"); return AVAssetReaderStatusFailed; } // Initialize a reader with a track output NSError *err = noErr; m_reader = [[AVAssetReader alloc] initWithAsset:uasset error:&err]; if (!m_reader || err) { DDLogError(@"could not create asset reader (%i)\n", [err code]); return AVAssetReaderStatusFailed; } // Check tracks for valid format. Currently we only support all MP3 and AAC types, WAV and AIFF is too large to handle for (AVAssetTrack *track in uasset.tracks) { NSArray *formats = track.formatDescriptions; for (int i=0; i<[formats count]; i++) { CMFormatDescriptionRef format = (CMFormatDescriptionRef)[formats objectAtIndex:i]; // Check the format types CMMediaType mediaType = CMFormatDescriptionGetMediaType(format); FourCharCode mediaSubType = CMFormatDescriptionGetMediaSubType(format); DDLogVerbose(@"mediaType: %s, mediaSubType: %s", COFcc(mediaType), COFcc(mediaSubType)); if (mediaType == kCMMediaType_Audio) { if (mediaSubType == kEDSupportedMediaTypeAAC || mediaSubType == kEDSupportedMediaTypeMP3) { m_track = [track retain]; m_format = CFRetain(format); break; } } } if (m_track != nil && m_format != NULL) { break; } } if (m_track == nil || m_format == NULL) { return kEDLibraryAssetReader_UnsupportedFormat; } // Create an output for the found track m_output = [[AVAssetReaderTrackOutput alloc] initWithTrack:m_track outputSettings:nil]; [m_reader addOutput:m_output]; // Start reading if (![m_reader startReading]) { DDLogError(@"could not start reading asset"); return kEDLibraryAssetReader_CouldNotStartReading; } return 0; } - (OSStatus)copyNextSampleBufferRepresentation:(CMSampleBufferRepresentationRef *)repOut { pthread_mutex_lock(&m_mtx); OSStatus err = noErr; AVAssetReaderStatus status = m_reader.status; if (m_invalid) { pthread_mutex_unlock(&m_mtx); return kEDLibraryAssetReader_Invalidated; } else if (status != AVAssetReaderStatusReading) { pthread_mutex_unlock(&m_mtx); return kEDLibraryAssetReader_NoMoreSampleBuffers; } // Read the next sample buffer CMSampleBufferRef sbuf = [m_output copyNextSampleBuffer]; if (sbuf == NULL) { pthread_mutex_unlock(&m_mtx); return kEDLibraryAssetReader_NoMoreSampleBuffers; } CMSampleBufferRepresentationRef srep = CMSampleBufferRepresentationCreateWithSampleBuffer(sbuf); if (srep && repOut != NULL) { *repOut = srep; } else { DDLogError(@"CMSampleBufferRef corrupted"); EDCFShow(sbuf); err = kEDLibraryAssetReader_BufferCorrupted; } CFRelease(sbuf); pthread_mutex_unlock(&m_mtx); return err; } </code></pre>

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