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iOS视频编辑之添加音轨的方法

时间:2022-06-26 05:51:32 编辑:袖梨 来源:一聚教程网

之前各种事情在身,发现好久没更新文章了,临近年末,就把最近做的视频处理相关的内容整理一下吧~

最近在做视频编辑处理相关的开发,其中之一就是音视频合成,需求是用户可以选择将相册中的视频,然后将一段音乐片段加入其中,并可以实时调整视频原声以及添加的音乐音量,最后合成为一个视频。

分析

首先对于视频处理,万能的ffmpeg肯定可以实现,但依赖ffmpeg并用一段magic一样的语句维护扩展都十分有限,对ffmpeg结构不熟悉的话大量c的api也会无从下手,适合熟悉ffmpeg并且对AVFoundation陌生者使用。

其次的最优方案就是AVFoundation了,作为苹果音视频编辑的利器可谓十分强大,官方有一 demo利用AVAudioEngine来实现音频的混音,甚至可以对pcm数据进行编辑,但是缺点也很明显:1 和视频没什么关系,还得启一个AVAudioPlayerNode来播放(那还不如单独用AVAudioPlayer得了) 2 并没有对音频如“美声,变音”之类的需求。所以不作为考虑范围,不过可以实现一些特殊音效还是很厉害的,感兴趣可以下来官方demo-Using AVAudioEngine for Playback, Mixing and Recording (AVAEMixerSample) 看看。

我最后选用的方案就是AVAudioMix,熟悉AVPlayer以及AVPlayerItem的话可能会注意到AVAudioMix 是作为属性存在于AVPlayerItem的分类中。

/*!
 @property audioMix
 @abstract Indicates the audio mix parameters to be applied during playback
 @discussion
  The inputParameters of the AVAudioMix must have trackIDs that correspond to a track of the receiver's asset. Otherwise they will be ignored. (See AVAudioMix.h for the declaration of AVAudioMixInputParameters and AVPlayerItem's asset property.)
 */
@property (nonatomic, copy, nullable) AVAudioMix *audioMix;

"Indicates the audio mix parameters to be applied during playback" 表明audioMix是可以在播放的时设置,需要注意的就是trackID需要对应。

补充:可能有人觉得最简单的是同时创建一个AVPlayer负责播放视频,一个AVAudioPlayer播放音乐;当然这种方法是可以实现基本需求,但完美出同步这俩个播放器的状态会是一个问题,而且最终还是要经历混音写文件过程,从逻辑上看十分糟糕。

播放实现

为了表述清晰下面省略AVPlayer等没太大关系的代码,同样也可以下载我的 demo 来查看所有内容。

流程如下:
1 创建视频以及音频的AVURLAsset

AVURLAsset *videoAsset = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"demo" ofType:@"mp4"]]];
AVURLAsset *musicAsset = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"music" ofType:@"mp3"]]];

2 声明并实例化音视频处理的核心类

@property (nonatomic, readwrite, strong) AVMutableComposition *composition;
@property (nonatomic, readwrite, strong) AVMutableVideoComposition *videoComposition;
@property (nonatomic, readwrite, strong) AVMutableAudioMix *audioMix;
AVMutableComposition *composition = [AVMutableComposition composition];
AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];

3 创建1条视频处理轨道以及2条音频处理轨道(视频原声+添加的音乐这俩条音轨)

AVMutableCompositionTrack *compositionVideoTracks = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *compositionAudioTracks[2];
compositionAudioTracks[0] = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
compositionAudioTracks[1] = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

4 根据之前创建好的视频以及音频资源(AVURLAsset)实例化一条视频轨道以及2条音频轨道

AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[compositionVideoTracks insertTimeRange:self.videoTimeRange ofTrack:videoTrack atTime:kCMTimeZero error:&error];
    
AVAssetTrack *audioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
[_comTrack1 insertTimeRange:self.videoTimeRange ofTrack:audioTrack atTime:kCMTimeZero error:&error];
    
AVAssetTrack *musicTrack = [[self.musicAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
[_comTrack2 insertTimeRange:self.videoTimeRange ofTrack:musicTrack atTime:kCMTimeZero error:&error];

5 配置AVMutableAudioMix参数,注意这里的trackID一定得是上面创建的AVMutableCompositionTrack对应的trackID,而不是AVAssetTrack中的trackID,之前使用AVAssetTrack出过很奇怪的问题,而后在StackOverFlow上找到了这个解决方案

 NSMutableArray *trackMixArray = [NSMutableArray array];
  {
    AVMutableAudioMixInputParameters *trackMix1 = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:_comTrack1];
    trackMix1.trackID = _comTrack1.trackID;
    [trackMix1 setVolume:_videoVolume atTime:kCMTimeZero];
    [trackMixArray addObject:trackMix1];
    
    AVMutableAudioMixInputParameters *trackMix2 = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:_comTrack2];
    trackMix2.trackID = _comTrack2.trackID;
    [trackMix2 setVolume:_musicVolume atTime:kCMTimeZero];
    [trackMixArray addObject:trackMix2];
  }
  
 audioMix.inputParameters = trackMixArray;

6 构建AVPlayerItem, 设置asset以及最重要的audioMix,然后交给AVPlayer就可以同时播放视频与音乐了!

- (AVPlayerItem *)playerItem {
  if (!_currentItem) {
    AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:self.composition];
    playerItem.videoComposition = self.videoComposition;
    playerItem.audioMix = self.audioMix;
    _currentItem = playerItem;
  }
  return _currentItem;
}

7 播放时调整音量,这里其实和第5步一样,重新配置AVMutableAudioMix参数后赋值给AVPlayerItem,设置音乐音量同理

- (void)setVideoVolume:(CGFloat)volume {
  NSMutableArray *allAudioParams = [NSMutableArray array];
  
  AVMutableAudioMixInputParameters *audioInputParams =
  [AVMutableAudioMixInputParameters audioMixInputParameters];
  [audioInputParams setTrackID:_comTrack1.trackID];
  _videoVolume = volume;
  [audioInputParams setVolume:_videoVolume atTime:kCMTimeZero];
  [allAudioParams addObject:audioInputParams];
  
  AVMutableAudioMixInputParameters *audioInputParams2 =
  [AVMutableAudioMixInputParameters audioMixInputParameters];
  [audioInputParams2 setTrackID:_comTrack2.trackID];
  [audioInputParams2 setVolume:_musicVolume atTime:kCMTimeZero];
  [allAudioParams addObject:audioInputParams2];
  
  AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
  [audioMix setInputParameters:allAudioParams];
  
  [_currentItem setAudioMix:audioMix];
}

导出实现

这里直接使用AVAssetExportSession来导出视频,与设置AVPlayerItem的audioMix属性相同,将audioMix设置给AVAssetExportSession实例即可导出混合的视频了

  NSURL *outputFileUrl = [NSURL fileURLWithPath:outputPath];  
  AVAssetExportSession *_assetExport =[[AVAssetExportSession alloc]initWithAsset:self.composition presetName:AVAssetExportPreset1280x720];
  _assetExport.outputFileType = AVFileTypeMPEG4;
  _assetExport.audioMix = _currentItem.audioMix;
  _assetExport.outputURL = outputFileUrl;
  _assetExport.shouldOptimizeForNetworkUse = YES;  
  [_assetExport exportAsynchronouslyWithCompletionHandler:^{
    //
  }];
最后贴上Demo地址 https://github.com/lucifron1994/VideoMixAudioDemo

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