iOS 多条音频拼接为一条音频进行播放

场景

把多条mp3音频合并为一条保存并进行播放

解决方案

1. 首先把全部音频路径生成为一个数组：

NSMutableArray * fileUrlArr = @[].mutableCopy;
    [mp3NameArr enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSString *mp3Name = [NSString stringWithFormat:@"%@",obj];
    
        // mp3路径
        NSString *audioFileURL = [[NSBundle mainBundle] pathForResource:mp3Name ofType:@"mp3"];
        [fileUrlArr addObject:audioFileURL];
    }];

2. 通过以下方法合并音频，保存在一个随机文件中，因为文件如果已存在或者文件目录写入失败，会出现【AVAssetExportSessionStatusFailed】错误码

///合并音频
- (void) mergeAVAssetWithSourceURLs:(NSArray *)sourceURLsArr completed:(void (^)(NSString * outputFileUrlStr)) completed{
    //创建音频轨道,并获取多个音频素材的轨道
    AVMutableComposition *composition = [AVMutableComposition composition];
    //音频插入的开始时间,用于记录每次添加音频文件的开始时间
    __block CMTime beginTime = kCMTimeZero;
    [sourceURLsArr enumerateObjectsUsingBlock:^(id  _Nonnull audioFileURL, NSUInteger idx, BOOL * _Nonnull stop) {
        //获取音频素材
        AVURLAsset *audioAsset1 = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:audioFileURL]];
        //音频轨道
        AVMutableCompositionTrack *audioTrack1 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:0];
        //获取音频素材轨道
        AVAssetTrack *audioAssetTrack1 = [[audioAsset1 tracksWithMediaType:AVMediaTypeAudio] firstObject];
        //音频合并- 插入音轨文件
        [audioTrack1 insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset1.duration) ofTrack:audioAssetTrack1 atTime:beginTime error:nil];
        // 记录尾部时间
        beginTime = CMTimeAdd(beginTime, audioAsset1.duration);
    }];
    //导出合并后的音频文件
    //音频文件目前只找到支持m4a 类型的
    AVAssetExportSession *session = [[AVAssetExportSession alloc]initWithAsset:composition presetName:AVAssetExportPresetAppleM4A];
    NSDateFormatter *formater = [[NSDateFormatter alloc] init];
    [formater setDateFormat:@"yyyy-MM-dd-HH:mm:ss-SSS"];
    NSString * timeFromDateStr = [formater stringFromDate:[NSDate date]];
    NSString *outPutFilePath = [NSHomeDirectory() stringByAppendingFormat:@"/tmp/sound-%@.mp4", timeFromDateStr];
    
    
    // 音频文件输出
    session.outputURL = [NSURL fileURLWithPath:outPutFilePath];
    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);
            if (completed) {
                completed(outPutFilePath);
            }
        } else {
            // 其他情况, 具体请看这里`AVAssetExportSessionStatus`.
            NSLog(@"合并失败----%ld", (long)session.status);
            if (completed) {
                completed(nil);
            }
        }
    }];
}

3. 输出合并音频

// 合并音频文件生成新的音频
    [self mergeAVAssetWithSourceURLs:musicArr completed:^(NSString *outputFileUrlStr) {
        if (!outputFileUrlStr) {
            NSLog(@"声音生成失败!");
            return;
        }
            self.audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:outputFileUrlStr] error:nil];
            [self.audioPlayer play];
    }];

参考：
https://www.cxyzjd.com/article/ismilesky/52780349
https://www.jianshu.com/p/3e357e3129b8
http://www.cocoachina.com/articles/17624