IOS视频添加背景音乐同时保留原音

//抽取原视频的音频与需要的音乐混合-(void)addmusic:(id)sender{   [MBProgressHUDshowHUDAddedTo:self.viewanimated:YES];     AVMutableComposition *composition =[AVMutableCompositioncomposition];   audioMixParams =[[NSMutableArrayalloc]initWithObjects:nil];      //录制的视频   NSURL *video_inputFileUrl =[NSURLfileURLWithPath:self.videoPath];   AVURLAsset *songAsset =[AVURLAssetURLAssetWithURL:video_inputFileUrloptions:nil];   CMTime startTime =CMTimeMakeWithSeconds(0,songAsset.duration.timescale);   CMTime trackDuration =songAsset.duration;      //获取视频中的音频素材   [selfsetUpAndAddAudioAtPath:video_inputFileUrltoComposition:compositionstart:startTimedura:trackDurationoffset:CMTimeMake(14*44100,44100)];      //本地要插入的音乐   NSString *bundleDirectory =[[NSBundlemainBundle]bundlePath];   NSString *path = [bundleDirectorystringByAppendingPathComponent:@"30secs.mp3"];   NSURL *assetURL2 =[NSURLfileURLWithPath:path];   //获取设置完的本地音乐素材   [selfsetUpAndAddAudioAtPath:assetURL2toComposition:compositionstart:startTimedura:trackDurationoffset:CMTimeMake(0,44100)];      //创建一个可变的音频混合   AVMutableAudioMix *audioMix =[AVMutableAudioMixaudioMix];   audioMix.inputParameters =[NSArrayarrayWithArray:audioMixParams];//从数组里取出处理后的音频轨道参数      //创建一个输出   AVAssetExportSession *exporter =[[AVAssetExportSessionalloc]                                initWithAsset:composition                                presetName:AVAssetExportPresetAppleM4A];   exporter.audioMix = audioMix;   exporter.outputFileType=@"com.apple.m4a-audio";   NSString* fileName =[NSStringstringWithFormat:@"%@.mov",@"overMix"];   //输出路径   NSString *exportFile =[NSStringstringWithFormat:@"%@/%@",[selfgetLibarayPath], fileName];      if([[NSFileManagerdefaultManager]fileExistsAtPath:exportFile]) {      [[NSFileManagerdefaultManager]removeItemAtPath:exportFileerror:nil];    }   NSLog(@"是否在主线程1%d",[NSThreadisMainThread]);   NSLog(@"输出路径===%@",exportFile);      NSURL *exportURL =[NSURLfileURLWithPath:exportFile];   exporter.outputURL = exportURL;   self.mixURL =exportURL;      [exporterexportAsynchronouslyWithCompletionHandler:^{       int exportStatus =(int)exporter.status;       switch (exportStatus){          caseAVAssetExportSessionStatusFailed:{             NSError *exportError =exporter.error;              NSLog(@"错误，信息: %@", exportError);             [MBProgressHUDhideHUDForView:self.viewanimated:YES];             break;           }          caseAVAssetExportSessionStatusCompleted:{             NSLog(@"是否在主线程2%d",[NSThreadisMainThread]);              NSLog(@"成功");             //最终混合              [selftheVideoWithMixMusic];             break;           }       }    }];}//最终音频和视频混合-(void)theVideoWithMixMusic{   NSError *error =nil;   NSFileManager *fileMgr =[NSFileManagerdefaultManager];   NSString *documentsDirectory =[NSHomeDirectory()                              stringByAppendingPathComponent:@"Documents"];   NSString *videoOutputPath =[documentsDirectorystringByAppendingPathComponent:@"test_output.mp4"];   if ([fileMgrremoveItemAtPath:videoOutputPatherror:&error]!=YES) {      NSLog(@"无法删除文件，错误信息：%@",[error localizedDescription]);    }      //声音来源路径（最终混合的音频）   NSURL   *audio_inputFileUrl =self.mixURL;      //视频来源路径   NSURL   *video_inputFileUrl = [NSURLfileURLWithPath:self.videoPath];      //最终合成输出路径   NSString *outputFilePath =[documentsDirectorystringByAppendingPathComponent:@"final_video.mp4"];   NSURL   *outputFileUrl = [NSURLfileURLWithPath:outputFilePath];      if([[NSFileManagerdefaultManager]fileExistsAtPath:outputFilePath])      [[NSFileManagerdefaultManager]removeItemAtPath:outputFilePatherror:nil];      CMTime nextClipStartTime =kCMTimeZero;      //创建可变的音频视频组合   AVMutableComposition* mixComposition =[AVMutableCompositioncomposition];      //视频采集   AVURLAsset* videoAsset =[[AVURLAssetalloc]initWithURL:video_inputFileUrloptions:nil];   CMTimeRange video_timeRange =CMTimeRangeMake(kCMTimeZero,videoAsset.duration);   AVMutableCompositionTrack*a_compositionVideoTrack = [mixCompositionaddMutableTrackWithMediaType:AVMediaTypeVideopreferredTrackID:kCMPersistentTrackID_Invalid];   [a_compositionVideoTrackinsertTimeRange:video_timeRangeofTrack:[[videoAssettracksWithMediaType:AVMediaTypeVideo]objectAtIndex:0]atTime:nextClipStartTimeerror:nil];      //声音采集   AVURLAsset* audioAsset =[[AVURLAssetalloc]initWithURL:audio_inputFileUrloptions:nil];   CMTimeRange audio_timeRange =CMTimeRangeMake(kCMTimeZero,videoAsset.duration);//声音长度截取范围==视频长度   AVMutableCompositionTrack*b_compositionAudioTrack = [mixCompositionaddMutableTrackWithMediaType:AVMediaTypeAudiopreferredTrackID:kCMPersistentTrackID_Invalid];   [b_compositionAudioTrackinsertTimeRange:audio_timeRangeofTrack:[[audioAssettracksWithMediaType:AVMediaTypeAudio]objectAtIndex:0]atTime:nextClipStartTimeerror:nil];      //创建一个输出   AVAssetExportSession* _assetExport =[[AVAssetExportSessionalloc]initWithAsset:mixCompositionpresetName:AVAssetExportPresetMediumQuality];   _assetExport.outputFileType =AVFileTypeQuickTimeMovie;   _assetExport.outputURL =outputFileUrl;   _assetExport.shouldOptimizeForNetworkUse=YES;   self.theEndVideoURL=outputFileUrl;      [_assetExportexportAsynchronouslyWithCompletionHandler:    ^(void ) {       [MBProgressHUDhideHUDForView:self.viewanimated:YES];       //播放        NSURL*url = [NSURLfileURLWithPath:outputFilePath];       MPMoviePlayerViewController *theMovie =[[MPMoviePlayerViewControlleralloc]initWithContentURL:url];       [selfpresentMoviePlayerViewControllerAnimated:theMovie];       theMovie.moviePlayer.movieSourceType=MPMovieSourceTypeFile;       [theMovie.moviePlayerplay];    }    ];   NSLog(@"完成！输出路径==%@",outputFilePath);}//通过文件路径建立和添加音频素材- (void)setUpAndAddAudioAtPath:(NSURL*)assetURLtoComposition:(AVMutableComposition*)composition start:(CMTime)startdura:(CMTime)duraoffset:(CMTime)offset{      AVURLAsset *songAsset =[AVURLAssetURLAssetWithURL:assetURLoptions:nil];      AVMutableCompositionTrack *track =[compositionaddMutableTrackWithMediaType:AVMediaTypeAudiopreferredTrackID:kCMPersistentTrackID_Invalid];   AVAssetTrack *sourceAudioTrack =[[songAssettracksWithMediaType:AVMediaTypeAudio]objectAtIndex:0];      NSError *error =nil;   BOOL ok =NO;      CMTime startTime = start;   CMTime trackDuration = dura;   CMTimeRange tRange =CMTimeRangeMake(startTime,trackDuration);      //设置音量   //AVMutableAudioMixInputParameters（输入参数可变的音频混合）   //audioMixInputParametersWithTrack（音频混音输入参数与轨道）   AVMutableAudioMixInputParameters *trackMix =[AVMutableAudioMixInputParametersaudioMixInputParametersWithTrack:track];    [trackMixsetVolume:0.8fatTime:startTime];      //素材加入数组   [audioMixParamsaddObject:trackMix];      //Insert audio into track  //offsetCMTimeMake(0, 44100)    ok = [trackinsertTimeRange:tRangeofTrack:sourceAudioTrackatTime:kCMTimeInvaliderror:&error];}#pragma mark - 保存路径-(NSString*)getLibarayPath{   NSFileManager *fileManager =[NSFileManagerdefaultManager];      NSArray* paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);   NSString* path = [pathsobjectAtIndex:0];      NSString *movDirectory = [pathstringByAppendingPathComponent:@"tmpMovMix"];      [fileManagercreateDirectoryAtPath:movDirectorywithIntermediateDirectories:YESattributes:nilerror:nil];      return movDirectory; }