iOS音频合成(音频拼接)

iOS 音频拼接

基本知识
AVAsset
正如官网文档所说——"AVAsset is an abstract class to represent timed audiovisual media such as videos and sounds. Each asset contains a collection of tracks that are intended to be presented or processed together, each of a uniform media type, including but not limited to audio, video, text, closed captions, and subtitles".
大致意思就是说AVAsset是AVFoundation中的一个抽象类，用来代表多媒体资源，比如，音频，视频等。
AVURLAsset
AVURLAsset是AVAsset的子类，是一个具体类，用URL来进行初始化。
AVMutableComposition
AVMutableComposition结合了媒体数据，可以看成是track(音频轨道)的集合，用来合成音视频。
AVMutableCompositionTrack
AVMutableCompositionTrack用来表示一个track，包含了媒体类型、音轨标识符等信息，可以插入、删除、缩放track片段。
AVAssetTrack
AVAssetTrack表示素材轨道。
AVAssetExportSession
AVAssetExportSession用来对一个AVAsset源对象进行转码，并导出为事先设置好的格式。

简单使用

//MARK:音频凭借
- (void)audioMergeClick{
//1.获取本地音频素材
    NSString *audioPath1 = [[NSBundle mainBundle]pathForResource:@"一" ofType:@"mp3"];
    NSString *audioPath2 = [[NSBundle mainBundle]pathForResource:@"元" ofType:@"mp3"];
    AVURLAsset *audioAsset1 = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:audioPath1]];
    AVURLAsset *audioAsset2 = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:audioPath2]];
//2.创建两个音频轨道,并获取两个音频素材的轨道
    AVMutableComposition *composition = [AVMutableComposition composition];
    //音频轨道
    AVMutableCompositionTrack *audioTrack1 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:0];
    AVMutableCompositionTrack *audioTrack2 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:0];
    //获取音频素材轨道
    AVAssetTrack *audioAssetTrack1 = [[audioAsset1 tracksWithMediaType:AVMediaTypeAudio] firstObject];
    AVAssetTrack *audioAssetTrack2 = [[audioAsset2 tracksWithMediaType:AVMediaTypeAudio]firstObject];
//3.将两段音频插入音轨文件,进行合并
    //音频合并- 插入音轨文件
    // `startTime`参数要设置为第一段音频的时长，即`audioAsset1.duration`, 表示将第二段音频插入到第一段音频的尾部。

    [audioTrack1 insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset1.duration) ofTrack:audioAssetTrack1 atTime:kCMTimeZero error:nil];
    [audioTrack2 insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset2.duration) ofTrack:audioAssetTrack2 atTime:audioAsset1.duration error:nil];
//4. 导出合并后的音频文件
    //`presetName`要和之后的`session.outputFileType`相对应
    //音频文件目前只找到支持m4a 类型的
    AVAssetExportSession *session = [[AVAssetExportSession alloc]initWithAsset:composition presetName:AVAssetExportPresetAppleM4A];
    
    NSString *outPutFilePath = [[self.filePath stringByDeletingLastPathComponent] stringByAppendingPathComponent:@"xindong.m4a"];
    
    if ([[NSFileManager defaultManager] fileExistsAtPath:outPutFilePath]) {
        [[NSFileManager defaultManager] removeItemAtPath:outPutFilePath error:nil];
    }
    // 查看当前session支持的fileType类型
    NSLog(@"---%@",[session supportedFileTypes]);
    session.outputURL = [NSURL fileURLWithPath:self.filePath];
    session.outputFileType = AVFileTypeAppleM4A; //与上述的`present`相对应
    session.shouldOptimizeForNetworkUse = YES;   //优化网络
    [session exportAsynchronouslyWithCompletionHandler:^{
        if (session.status == AVAssetExportSessionStatusCompleted) {
            NSLog(@"合并成功----%@", outPutFilePath);
            _audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:outPutFilePath] error:nil];
            [_audioPlayer play];
        } else {
            // 其他情况, 具体请看这里`AVAssetExportSessionStatus`.
        }
    }];
    
}


- (NSString *)filePath {
    if (!_filePath) {
        _filePath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) firstObject];
        NSString *folderName = [_filePath stringByAppendingPathComponent:@"MergeAudio"];
        BOOL isCreateSuccess = [kFileManager createDirectoryAtPath:folderName withIntermediateDirectories:YES attributes:nil error:nil];
        if (isCreateSuccess) _filePath = [folderName stringByAppendingPathComponent:@"xindong.m4a"];
    }
    return _filePath;
}

简单音频拼接介绍:

http://www.cocoachina.com/ios/20160922/17624.html

音频与音频, 音频与视频

http://www.jianshu.com/p/76e0c4e684db