前面的文章我介紹了如何將多張圖片合成視頻，這篇文章將繼續(xù)介紹如何將同時(shí)錄制的音頻合成到視頻文件中（音頻的錄制就不做介紹了，使用AVAudioRecorder就可錄制音頻）。

下面直接貼代碼介紹吧

+ (void)mergeVideo:(NSString *)videoPath andAudio:(NSString *)audioPath withCompletion:(ZYSExportVideoCompletion)completion {
    
    // 視頻和音頻源文件
    NSURL *videoURL = [NSURL fileURLWithPath:videoPath];
    NSURL *audioURL = [NSURL fileURLWithPath:audioPath];
    
    // 最終合成后文件的輸出路徑
    NSString *docPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    NSString *outputPath = [docPath stringByAppendingPathComponent:@"ScreenRecord.mp4"];
    NSFileManager *fm = [NSFileManager defaultManager];
    if ([fm fileExistsAtPath:outputPath]) {
        if (![fm removeItemAtPath:outputPath error:nil]) {
            NSLog(@"remove old output file failed.");
        }
    }
    NSURL *outputURL = [NSURL fileURLWithPath:outputPath];
    
    
    // 時(shí)間起點(diǎn)
    CMTime startTime = kCMTimeZero;
    
    // 創(chuàng)建音視頻組合操作類
    AVMutableComposition *composition = [AVMutableComposition composition];
    
    
    /// 視頻采集
    AVURLAsset *videoAsset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];
    
    // 獲取視頻時(shí)間范圍
    CMTimeRange videoTimeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);
    
    // 創(chuàng)建視頻通道
    AVMutableCompositionTrack *videoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    
    // 創(chuàng)建視頻采集通道
    AVAssetTrack *videoAssetTrack = [videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject;
    
    // 將采集的視頻數(shù)據(jù)加入到可變軌道中
    [videoTrack insertTimeRange:videoTimeRange ofTrack:videoAssetTrack atTime:startTime error:nil];
    
    
    /// 音頻采集
    AVURLAsset *audioAsset = [[AVURLAsset alloc] initWithURL:audioURL options:nil];
    
    // 音頻時(shí)間范圍
    CMTimeRange audioTimeRange = CMTimeRangeMake(kCMTimeZero, audioAsset.duration);
    
    // 創(chuàng)建音頻通道
    AVMutableCompositionTrack *audioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    
    // 獲取音頻采集通道
    AVAssetTrack *audioAssetTrack = [audioAsset tracksWithMediaType:AVMediaTypeAudio].firstObject;
    
    // 將采集的音頻數(shù)據(jù)添加到可變軌道中
    [audioTrack insertTimeRange:audioTimeRange ofTrack:audioAssetTrack atTime:startTime error:nil];
    
    // 創(chuàng)建一個(gè)視頻輸出
    AVAssetExportSession *assetExport = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetMediumQuality];
    
    // 視頻輸出類型
    assetExport.outputFileType = AVFileTypeMPEG4;
    
    // 視頻輸出地址
    assetExport.outputURL = outputURL;
    
    // 是否優(yōu)化視頻
    assetExport.shouldOptimizeForNetworkUse = YES;
    
    // 導(dǎo)出視頻
    [assetExport exportAsynchronouslyWithCompletionHandler:^{
        // 刪除原視頻、音頻文件
        if ([fm fileExistsAtPath:videoPath]) {
            if (![fm removeItemAtPath:videoPath error:nil]) {
                NSLog(@"remove video.mp4 failed.");
            }
        }
        
        if ([fm fileExistsAtPath:audioPath]) {
            if (![fm removeItemAtPath:audioPath error:nil]) {
                NSLog(@"remove audio.wav failed.");
            }
        }
        
        if (completion) {
            completion(outputPath);
        }
    }];
}