iOS 中 如何从视频中提取音频？

.h文件
/**

提取视频中的音频

@param videoPath 视频路径
@param completionHandle 完成回调
*/

+(void)accessAudioFromVideo:(NSURL *)videoPath completion:(void (^)(NSURL *outputPath,BOOL isSucceed)) completionHandle;

.m文件
需要导入系统的#import <Photos/Photos.h>
/**

提取视频中的音频

@param videoPath 视频路径
@param completionHandle 完成回调
*/

+(void)accessAudioFromVideo:(NSURL *)videoPath completion:(void (^)(NSURL *outputPath,BOOL isSucceed)) completionHandle{        AVAsset *videoAsset = [AVAsset assetWithURL:videoPath];    //1创立一个AVMutableComposition    AVMutableComposition *mixComposition = [[AVMutableComposition alloc]init];    //2 创立一个轨道,类型为AVMediaTypeAudio    AVMutableCompositionTrack *audioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];        //获取videoPath的音频插入轨道    [audioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];        //4创立输出路径    NSURL *outputURL = [self exporterPath:@"mp4"];        //5创立输出对象    AVAssetExportSession *exporter = [[AVAssetExportSession alloc]initWithAsset:mixComposition presetName:AVAssetExportPresetAppleM4A];    exporter.outputURL = outputURL ;    exporter.outputFileType = AVFileTypeAppleM4A;    exporter.shouldOptimizeForNetworkUse = YES;    [exporter exportAsynchronouslyWithCompletionHandler:^{        if (exporter.status == AVAssetExportSessionStatusCompleted) {            NSURL *outputURL = exporter.outputURL;            completionHandle(outputURL,YES);        }else {            NSLog(@"失败%@",exporter.error.description);            completionHandle(outputURL,NO);        }    }];    }//  输出路径+ (NSURL *)exporterPath:(NSString *)filename{    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];    formatter.dateFormat = @"yyyyMMddHHmmss";    NSString *str = [formatter stringFromDate:[NSDate date]];    NSString *fileName = [NSString stringWithFormat:@"selfMusic%@.%@",str,filename];    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *docPath = [paths firstObject];    //这个是录制视频时存储到本地的video    NSString *path = [NSString stringWithFormat:@"%@/KSYShortVideoCache",docPath];    //判断文件夹能否存在，不存在就创立    //创立附件存储目录    if (![[NSFileManager defaultManager] fileExistsAtPath:path]) {        [[NSFileManager defaultManager] createDirectoryAtPath:path withIntermediateDirectories:YES attributes:nil error:nil];    }    NSString *outputFilePath = [path stringByAppendingPathComponent:fileName];    return [NSURL fileURLWithPath:outputFilePath];}