I am trying to use an AVPlayerItem and AVPlayerItemVideoOutput to grab frame images of a video. Most examples I see attach a CADisplayLink and simply pass the time of the display link to the itemTime function that exists on AVPlayerItemVideoOutput or they pass CACurrentMediaTime() instead.
let itemTime = playerItemVideoOutput.itemTime(forHostTime: CACurrentMediaTime())
The problem with this to me is I would like to grab a specific second of the video. In most functions if have seen you could simply build a time and get that frame. For Example:
CMTime(seconds: 10.0, preferredTimescale: 600)//10 seconds
However, this is not the way AVPlayerItemVideoOutput works. It seems to calculate it's own time from some reference point(probably when it is added and available on the player). I need help understanding the time it needs to pass a specific frame to get of the video.
//get item time so that I can grab a specific frame of the video
if playerItemVideoOutput.hasNewPixelBuffer(forItemTime: itemTime),
let pixelBuffer = playerItemVideoOutput.copyPixelBuffer(forItemTime: itemTime,itemTimeForDisplay: nil) ,
case let i = CIImage(cvPixelBuffer: pixelBuffer){
}
Some might suggest to use AVAssetImageGenerator instead and this does work but I have bound the speed and efficient of the AVPlayerItemVideoOutput to be superior to grab the number of frames that I need.
You could try calling player.seek(to:) and then copyPixelBuffer with CACurrentMediaTime().
But I don't know how successful you're going to be if the player is playing from some point and you try to get pixel buffers from other points in the timeline.
I don't think AVPlayerItemVideoOutput is meant to be for truly "random access". It probably (reasonably) assumes that time will progress in the same way that it does for its AVPlayerItem.
Using an AVAssetReader with an AVAssetReaderTrackOutput however would let you seek relative to the asset's timeline by setting the reader's timeRange property.