////  ViewController.m//  iOS视频测试////  Created by apple on 15/8/19.//  Copyright (c) 2015年 tqh. All rights reserved.//#import "ViewController.h"#import 
     
      @interface ViewController ()@end@implementation ViewController//下载视频- (void)viewDidLoad {    [super viewDidLoad];    NSString *path = NSHomeDirectory();//主目录    NSLog(@"NSHomeDirectory:%@",path);    //获取沙盒中的路径        NSArray *storeFilePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);        NSString *doucumentsDirectiory = [storeFilePath objectAtIndex:0];        NSString *plistPath =[doucumentsDirectiory stringByAppendingPathComponent:@"mp4Test.mp4"];        NSFileManager *file = [NSFileManager defaultManager];        if ([file fileExistsAtPath:plistPath])            {        NSLog(@"沙盒中有视频");    }    else //若沙盒中没有            {        NSError *error;        NSFileManager *fileManager = [NSFileManager defaultManager];        NSString *bundle = [[NSBundle mainBundle] pathForResource:@"mp4Test" ofType:@"mp4"];        [fileManager copyItemAtPath:bundle toPath:plistPath error:&error];        NSLog(@"写入没有%d",[fileManager copyItemAtPath:bundle toPath:plistPath error:&error]);            }    NSString *newPlistPath =[doucumentsDirectiory stringByAppendingPathComponent:@"mp4Test5.mp4"];    [self lowQuailtyWithInputURL:[NSURL fileURLWithPath:plistPath] outputURL:[NSURL fileURLWithPath:newPlistPath] blockHandler:^(AVAssetExportSession *session) {        if (session.status == AVAssetExportSessionStatusCompleted)        {            NSLog(@"压缩完成");        }else if (session.status == AVAssetExportSessionStatusFailed) {            NSLog(@"压缩失败");        }    }];}#pragma mark - 视频压缩- (void) lowQuailtyWithInputURL:(NSURL*)inputURL                      outputURL:(NSURL*)outputURL                   blockHandler:(void (^)(AVAssetExportSession*))handler{    AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];    AVAssetExportSession *session = [[AVAssetExportSession alloc] initWithAsset:asset     presetName:AVAssetExportPresetLowQuality];    session.outputURL = outputURL;    session.outputFileType = AVFileTypeQuickTimeMovie;    [session exportAsynchronouslyWithCompletionHandler:^(void)     {         handler(session);     }];}@end
     

AVAssetExportPresetLowQuality：低质量压缩

AVF_EXPORT NSString *const AVAssetExportPresetLowQuality        NS_AVAILABLE_IOS(4_0);

AVF_EXPORT NSString *const AVAssetExportPresetMediumQuality     NS_AVAILABLE_IOS(4_0);

AVF_EXPORT NSString *const AVAssetExportPresetHighestQuality    NS_AVAILABLE_IOS(4_0);