iOS视频添加背景音乐同时保留原音

话不多说，请看代码：

//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;
}

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