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; }