HTTP live stream AVAsset - opencv

Question

I am implementing a n HTTP live streaming player with OSX using avplayer.
I am able to stream it properly seek and get duration timing etc.
Now i want to take screen shots and process the frames from it using OpenCV.
I went for using AVASSetImageGenerator. But there is no audio and video tracks with the AVAsset which is associated with player.currentItem.
The tracks are appearing in player.currentItem.tracks.
So i am not able to sue AVAssetGenerator. Can anybody help to find out a solution to extract screenshots and individual frames in such a scenario?
Please find the code below how i am initiating an HTTP live stream
Thanks in advance.
NSURL* url = [NSURL URLWithString:#"http://devimages.apple.com/iphone/samples/bipbop/bipbopall.m3u8"];
playeritem = [AVPlayerItem playerItemWithURL:url];
[playeritem addObserver:self forKeyPath:#"status" options:0 context:AVSPPlayerStatusContext];
[self setPlayer:[AVPlayer playerWithPlayerItem:playeritem]];
[self addObserver:self forKeyPath:#"player.rate" options:NSKeyValueObservingOptionNew context:AVSPPlayerRateContext];
[self addObserver:self forKeyPath:#"player.currentItem.status" options:NSKeyValueObservingOptionNew context:AVSPPlayerItemStatusContext];
AVPlayerLayer *newPlayerLayer = [AVPlayerLayer playerLayerWithPlayer:[self player]];
[newPlayerLayer setFrame:[[[self playerView] layer] bounds]];
[newPlayerLayer setAutoresizingMask:kCALayerWidthSizable | kCALayerHeightSizable];
[newPlayerLayer setHidden:YES];
[[[self playerView] layer] addSublayer:newPlayerLayer];
[self setPlayerLayer:newPlayerLayer];
[self addObserver:self forKeyPath:#"playerLayer.readyForDisplay" options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew context:AVSPPlayerLayerReadyForDisplay];
[self.player play];
Following is how i am checking whether video track is present with the Asset
case AVPlayerItemStatusReadyToPlay:
[self setTimeObserverToken:[[self player] addPeriodicTimeObserverForInterval:CMTimeMake(1, 10) queue:dispatch_get_main_queue() usingBlock:^(CMTime time) {
[[self timeSlider] setDoubleValue:CMTimeGetSeconds(time)];
NSLog(#"%f,%f,%f",[self currentTime],[self duration],[[self player] rate]);
AVPlayerItem *item = playeritem;
if(item.status == AVPlayerItemStatusReadyToPlay)
{
AVAsset *asset = (AVAsset *)item.asset;
long audiotracks = [[asset tracks] count];
long videotracks = [[asset availableMediaCharacteristicsWithMediaSelectionOptions]count];
NSLog(#"Track info Audio = %ld,Video=%ld",audiotracks,videotracks);
}
}]];
AVPlayerItem *item = self.player.currentItem;
if(item.status != AVPlayerItemStatusReadyToPlay)
return;
AVURLAsset *asset = (AVURLAsset *)item.asset;
long audiotracks = [[asset tracksWithMediaType:AVMediaTypeAudio]count];
long videotracks = [[asset tracksWithMediaType:AVMediaTypeVideo]count];
NSLog(#"Track info Audio = %ld,Video=%ld",audiotracks,videotracks);

Answer 1

This is an older question but in case someone needs help for that i have an answer
AVURLAsset *asset = /* Your Asset here! */;
AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
generator.requestedTimeToleranceAfter = kCMTimeZero;
generator.requestedTimeToleranceBefore = kCMTimeZero;
for (Float64 i = 0; i < CMTimeGetSeconds(asset.duration) * /* Put the FPS of the source video here */ ; i++){
#autoreleasepool {
CMTime time = CMTimeMake(i, /* Put the FPS of the source video here */);
NSError *err;
CMTime actualTime;
CGImageRef image = [generator copyCGImageAtTime:time actualTime:&actualTime error:&err];
// Do what you want with the image, for example save it as UIImage
UIImage *generatedImage = [[UIImage alloc] initWithCGImage:image];
CGImageRelease(image);
}
}
You can easily get the FPS of a Video by using this code:
float fps=0.00;
if (asset) {
AVAssetTrack * videoATrack = [asset tracksWithMediaType:AVMediaTypeVideo][0];
if(videoATrack)
{
fps = [videoATrack nominalFrameRate];
}
}
Hope that helps someone who is asking how to get all frames from a video or just some specific (with CMTime for example) frames. Please bear in mind, that saving all frames to an array can impact the memory hardly!