frangulyan frangulyan - 2 months ago 64
Objective-C Question

iOS: AVPlayer - getting a snapshot of the current frame of a video

I have spent the whole day and went through a lot of SO answers, Apple references, documentations, etc, but no success.

I want a simple thing: I am playing a video using AVPlayer and I want to pause it and get the current frame as

UIImage
. That's it.

My video is a m3u8 file located on the internet, it is played normally in the
AVPlayerLayer
without any problems.

What have I tried:


  1. AVAssetImageGenerator
    .
    It is not working, the method
    copyCGImageAtTime:actualTime: error:
    returns null image ref. According to the answer here
    AVAssetImageGenerator
    doesn't work for streaming videos.

  2. Taking snapshot of the player view. I tried first
    renderInContext:
    on
    AVPlayerLayer
    , but then I realized that it is not rendering this kind of "special" layers. Then I found a new method introduced in iOS 7 -
    drawViewHierarchyInRect:afterScreenUpdates:
    which should be able to render also the special layers, but no luck, still got the UI snapshot with blank black area where the video is shown.

  3. AVPlayerItemVideoOutput
    .
    I have added a video output for my
    AVPlayerItem
    , however whenever I call
    hasNewPixelBufferForItemTime:
    it returns
    NO
    . I guess the problem is again streaming video and I am not alone with this problem.

  4. AVAssetReader
    .
    I was thinking to try it but decided not to lose time after finding a related question here.



So isn't there any way to get a snapshot of something that I am anyway seeing right now on the screen? I can't believe this.

Answer

AVPlayerItemVideoOutput works fine for me from an m3u8. Maybe it's because I don't consult hasNewPixelBufferForItemTime and simply call copyPixelBufferForItemTime? This code produces a CVPixelBuffer instead of a UIImage, but there are answers that describe how to do that.

This answer mostly cribbed from here

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>

@interface ViewController ()

@property (nonatomic) AVPlayer *player;
@property (nonatomic) AVPlayerItem *playerItem;
@property (nonatomic) AVPlayerItemVideoOutput *playerOutput;

@end

@implementation ViewController
- (void)setupPlayerWithLoadedAsset:(AVAsset *)asset {
    NSDictionary* settings = @{ (id)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_32BGRA) };
    self.playerOutput = [[AVPlayerItemVideoOutput alloc] initWithPixelBufferAttributes:settings];
    self.playerItem = [AVPlayerItem playerItemWithAsset:asset];
    [self.playerItem addOutput:self.playerOutput];
    self.player = [AVPlayer playerWithPlayerItem:self.playerItem];

    AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:self.player];
    playerLayer.frame = self.view.frame;
    [self.view.layer addSublayer:playerLayer];

    [self.player play];
}

- (IBAction)grabFrame {
    CVPixelBufferRef buffer = [self.playerOutput copyPixelBufferForItemTime:[self.playerItem currentTime] itemTimeForDisplay:nil];
    NSLog(@"The image: %@", buffer);
}

- (void)viewDidLoad {
    [super viewDidLoad];


    NSURL *someUrl = [NSURL URLWithString:@"http://qthttp.apple.com.edgesuite.net/1010qwoeiuryfg/sl.m3u8"];
    AVURLAsset *asset = [AVURLAsset URLAssetWithURL:someUrl options:nil];

    [asset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObject:@"tracks"] completionHandler:^{

        NSError* error = nil;
        AVKeyValueStatus status = [asset statusOfValueForKey:@"tracks" error:&error];
        if (status == AVKeyValueStatusLoaded)
        {
            dispatch_async(dispatch_get_main_queue(), ^{
                [self setupPlayerWithLoadedAsset:asset];
            });
        }
        else
        {
            NSLog(@"%@ Failed to load the tracks.", self);
        }
    }];
}

@end