ios AVAssetExportSession的使用完整版

- (void)getVedioResource {
    UIAlertController *alertC = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];
    UIAlertAction *cacelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        [self dismissViewControllerAnimated:YES completion:nil];
    }];
    UIAlertAction *chooseVideo = [UIAlertAction actionWithTitle:@"选择本地视频" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        [self chooseVideo];
    }];
    UIAlertAction *startVideo = [UIAlertAction actionWithTitle:@"录制视频" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        [self startvideo];
    }];
    [alertC addAction:startVideo];
    [alertC addAction:chooseVideo];
    [alertC addAction:cacelAction];
    // 点击取消按钮
    [self presentViewController:alertC animated:YES completion:^{
    }];
}
//选择本地视频
- (void)chooseVideo {
    UIImagePickerController *ipc = [[UIImagePickerController alloc] init];
    ipc.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    NSArray *availableMedia = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];//Camera所支持的Media格式都有哪些,共有两个分别是@"public.image",@"public.movie"
    ipc.mediaTypes = [NSArray arrayWithObject:availableMedia[1]];//设置媒体类型为public.movie
    [self presentViewController:ipc animated:YES completion:nil];
    ipc.delegate = self;//设置委托
}
//录制视频
- (void)startvideo
{
    UIImagePickerController *ipc = [[UIImagePickerController alloc] init];
    ipc.sourceType = UIImagePickerControllerSourceTypeCamera;//sourcetype有三种分别是camera，photoLibrary和photoAlbum
    NSArray *availableMedia = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];//Camera所支持的Media格式都有哪些,共有两个分别是@"public.image",@"public.movie"
    ipc.mediaTypes = [NSArray arrayWithObject:availableMedia[1]];//设置媒体类型为public.movie
    [self presentViewController:ipc animated:YES completion:nil];
    ipc.videoMaximumDuration = 30.0f;//30秒
    ipc.delegate = self;//设置委托

}
//此方法可以获取文件的大小，返回的是单位是KB。
- (CGFloat) getFileSize:(NSString *)path
{
    NSLog(@"%@",path);
    NSFileManager *fileManager = [NSFileManager defaultManager];
    float filesize = -1.0;
    if ([fileManager fileExistsAtPath:path]) {
        NSDictionary *fileDic = [fileManager attributesOfItemAtPath:path error:nil];//获取文件的属性
        unsigned long long size = [[fileDic objectForKey:NSFileSize] longLongValue];
        filesize = 1.0*size/1024/1024;
    }else{
        NSLog(@"找不到文件");
    }
    return filesize;
}

//完成视频录制，并压缩后显示大小、时长
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSURL *sourceURL = [info objectForKey:UIImagePickerControllerMediaURL];
    NSLog(@"%@", [NSString stringWithFormat:@"%.2f kb", [self getFileSize:[sourceURL path]]]);
    NSURL *newVideoUrl ; //一般.mp4
    NSDateFormatter *formater = [[NSDateFormatter alloc] init];//用时间给文件全名，以免重复，在测试的时候其实可以判断文件是否存在若存在，则删除，重新生成文件即可
    [formater setDateFormat:@"yyyy-MM-dd-HH:mm:ss"];
    NSString *pathString = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/output-%@.mp4", [formater stringFromDate:[NSDate date]] ];
    newVideoUrl = [NSURL fileURLWithPath:pathString];//这个是保存在app自己的沙盒路径里，后面可以选择是否在上传后删除掉。我建议删除掉，免得占空间。
    [picker dismissViewControllerAnimated:YES completion:nil];
    [self convertVideoQuailtyWithInputURL:sourceURL outputURL:newVideoUrl completeHandler:nil];
}
- (void) convertVideoQuailtyWithInputURL:(NSURL*)inputURL
                               outputURL:(NSURL*)outputURL
                         completeHandler:(void (^)(AVAssetExportSession*))handler
{
    AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:inputURL options:nil];
    NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset];
    if ([compatiblePresets containsObject:AVAssetExportPresetHighestQuality]) {
        AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:avAsset presetName:AVAssetExportPresetMediumQuality];
        NSLog(@"---------%@",outputURL.path);
        exportSession.outputURL = outputURL;
        exportSession.outputFileType = AVFileTypeMPEG4;
        exportSession.shouldOptimizeForNetworkUse= YES;
        [exportSession exportAsynchronouslyWithCompletionHandler:^(void)
         {
             switch (exportSession.status) {
                 case AVAssetExportSessionStatusCancelled:
                     NSLog(@"AVAssetExportSessionStatusCancelled");
                     break;
                 case AVAssetExportSessionStatusUnknown:
                     NSLog(@"AVAssetExportSessionStatusUnknown");
                     break;
                 case AVAssetExportSessionStatusWaiting:
                     NSLog(@"AVAssetExportSessionStatusWaiting");
                     break;
                 case AVAssetExportSessionStatusExporting:
                     NSLog(@"AVAssetExportSessionStatusExporting");
                     break;
                 case AVAssetExportSessionStatusCompleted:
                     NSLog(@"AVAssetExportSessionStatusCompleted");
                     NSLog(@"%@", [NSString stringWithFormat:@"%.2f kb", [self getFileSize:[outputURL path]]]);
                     [self cutFileForWithVideo:[outputURL path]];
                     //UISaveVideoAtPathToSavedPhotosAlbum([outputURL path], self, nil, NULL);//这个是保存到手机相册
                     //上传
                     //                 [self alertUploadVideo:outputURL];


                     break;
                 case AVAssetExportSessionStatusFailed:
                     NSLog(@"AVAssetExportSessionStatusFailed");
                     NSLog(@"---%@",exportSession.error.description);
                     break;
             }
         }];
    }
}