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; 
}