AVPlayer实现播放视频和AVFoundation获取视频的buffer

这篇文章目的是用AVPlayer实现本地视频的播放，和使用AVFoundation获取视频的buffer；在这个获取视频buffer的过程中，因为不是摄像头取到的视频，所以走了一些弯路，希望写下来，给需要的人
项目本身的需求是获取到视频的buffer做进一步处理，并不需要播放视频，但是播放只是一句话，我注释掉了。
先看效果

1.0 加载本地视频，创建player 并播放

NSURL url = [[NSBundle mainBundle]URLForResource:@"Cat" withExtension:@"mp4"];AVPlayerItem item = [[AVPlayerItem alloc]initWithURL:url];AVPlayer player = [[AVPlayer alloc]initWithPlayerItem:item];_player = player;AVPlayerLayer layer = [AVPlayerLayer playerLayerWithPlayer:player];layer.frame = self.view.bounds;// 添加layer[self.view.layer addSublayer:layer];[player play];

1.1 创建videooutput

AVPlayerItemVideoOutput *videoOutput = [[AVPlayerItemVideoOutput alloc]init];    [item addOutput:videoOutput];    self.videoOutput = videoOutput;

1.2 用定时器定时取出某一时刻的CMSampleBufferRef
display link 对象负责在每帧需要绘制的时候给我们发送消息，这个消息是按照显示器的刷新频率同步进行发送的

  CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(displayLinkDidrefresh:)];    [link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];-(void)displayLinkDidrefresh:(CADisplayLink*)link{    CMTime itemTime = _player.currentItem.currentTime;        CVPixelBufferRef pixelBuffer = [_videoOutput copyPixelBufferForItemTime:itemTime itemTimeForDisplay:nil];// 拿到buffer后 我们可以调用gpuImage或者OpenGL做进一步的操作；//  可以将buffer转换为UIimage//    CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];//    CIContext *temporaryContext = [CIContext contextWithOptions:nil];//    CGImageRef videoImage = [temporaryContext//                             createCGImage:ciImage//                             fromRect:CGRectMake(0, 0,//                                                 CVPixelBufferGetWidth(pixelBuffer),//                                                 CVPixelBufferGetHeight(pixelBuffer))];//    //    //当前帧的画面//    UIImage *currentImage = [UIImage imageWithCGImage:videoImage];//    CGImageRelease(videoImage);//    用完记得及时释放掉否则内存会暴涨    CVPixelBufferRelease(pixelBuffer);}

全部代码如下：

////  Created by Leon.li on 2017/4/12.//  Copyright © 2017年 Leon.li. All rights reserved.//#import "XBHomeViewController.h"#import <AVFoundation/AVFoundation.h>@interface XBHomeViewController ()@property (nonatomic,strong)AVPlayer *player;@property (nonatomic,strong)AVPlayerItemVideoOutput *videoOutput;//@property (nonatomic,assign)CVPixelBufferRef pixelBuffer;@end@implementation XBHomeViewController- (void)viewDidLoad {    [super viewDidLoad];        self.view.backgroundColor = [UIColor brownColor];    //    [self loadVideoFile];        [self loadAVPlayer];        // Do any additional setup after loading the view.}-(void)loadAVPlayer{    NSURL *url = [[NSBundle mainBundle]URLForResource:@"Cat" withExtension:@"mp4"];    AVPlayerItem *item = [[AVPlayerItem alloc]initWithURL:url];    AVPlayer *player = [[AVPlayer alloc]initWithPlayerItem:item];    _player = player;    AVPlayerLayer *layer = [AVPlayerLayer playerLayerWithPlayer:player];    layer.frame = self.view.bounds;    // 添加layer    [self.view.layer addSublayer:layer];    [player play];    AVPlayerItemVideoOutput *videoOutput = [[AVPlayerItemVideoOutput alloc]init];    [item addOutput:videoOutput];    self.videoOutput = videoOutput;//    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(displayLinkDidrefresh:)];    [link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];// 这里为了循环播放    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(rePlay) name:AVPlayerItemDidPlayToEndTimeNotification object:nil];}-(void)displayLinkDidrefresh:(CADisplayLink*)link{    CMTime itemTime = _player.currentItem.currentTime;        CVPixelBufferRef pixelBuffer = [_videoOutput copyPixelBufferForItemTime:itemTime itemTimeForDisplay:nil];    //  可以将buffer转换为UIimage//    CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];//    CIContext *temporaryContext = [CIContext contextWithOptions:nil];//    CGImageRef videoImage = [temporaryContext//                             createCGImage:ciImage//                             fromRect:CGRectMake(0, 0,//                                                 CVPixelBufferGetWidth(pixelBuffer),//                                                 CVPixelBufferGetHeight(pixelBuffer))];//    //    //当前帧的画面//    UIImage *currentImage = [UIImage imageWithCGImage:videoImage];//    CGImageRelease(videoImage);//    用完记得及时释放掉否则内存会暴涨    CVPixelBufferRelease(pixelBuffer);        }-(void)rePlay{    typeof(self) weakSelf = self;    [self.player seekToTime:kCMTimeZero completionHandler:^(BOOL finished) {        [weakSelf.player play];    }];    }-(void)dealloc{    [[NSNotificationCenter defaultCenter] removeObserver:self];}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}/*#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {    // Get the new view controller using [segue destinationViewController].    // Pass the selected object to the new view controller.}*/@end