Enables smooth frame-by-frame scrubbing (in both directions) – similar to Apple's applications.

AVPlayer+Scrubbing.swift

public enum Direction {
    case forward
    case backward
}

internal var player: AVPlayer?

private var isSeekInProgress = false
private var chaseTime = kCMTimeZero
private var preferredFrameRate: Float = 23.98

public func seek(to time: CMTime) {
    seekSmoothlyToTime(newChaseTime: time)
}

public func stepByFrame(in direction: Direction) {
    let frameRate = preferredFrameRate
        ?? player?.currentItem?.tracks
            .first(where: { $0.assetTrack.mediaType == .video })?
            .currentVideoFrameRate
        ?? -1

    let time = player?.currentItem?.currentTime() ?? kCMTimeZero
    let seconds = Double(1) / Double(frameRate)
    let timescale = Double(seconds) / Double(time.timescale) < 1 ? 600 : time.timescale
    let oneFrame = CMTime(seconds: seconds, preferredTimescale: timescale)
    let next = direction == .forward
        ? CMTimeAdd(time, oneFrame)
        : CMTimeSubtract(time, oneFrame)

    seekSmoothlyToTime(newChaseTime: next)
}

private func seekSmoothlyToTime(newChaseTime: CMTime) {
    if CMTimeCompare(newChaseTime, chaseTime) != 0 {
        chaseTime = newChaseTime

        if !isSeekInProgress {
            trySeekToChaseTime()
        }
    }
}

private func trySeekToChaseTime() {
    guard player?.status == .readyToPlay else { return }
    actuallySeekToTime()
}

private func actuallySeekToTime() {
    isSeekInProgress = true
    let seekTimeInProgress = chaseTime

    player?.seek(to: seekTimeInProgress, toleranceBefore: kCMTimeZero, toleranceAfter: kCMTimeZero) { [weak self] _ in
        guard let `self` = self else { return }

        if CMTimeCompare(seekTimeInProgress, self.chaseTime) == 0 {
            self.isSeekInProgress = false
        } else {
            self.trySeekToChaseTime()
        }
    }
}

This was actually recommended by someone on the AV team but I think your approach is different in that you use very different tolerances.

I guess this could be recommended if you want to avoid downloading too many segments while seeking, but this of course depends on the desired user experience. As far as I can see AVPlayerViewController nowadays seem to avoid seek cancellation, probably as described in Apple dedicated Q&A article.

Side note btw regarding AVPlayerController. I believe at one point I discovered that actually they use the thumbnail generator to improve the perceived responsiveness.

Note sure if they use AVAssetImageGenerator directly but if HLS streams contain I-frames the player surely uses them (even without changing the actual player speed to values > 2, which I initially thought might be required).

BTW you can easily test the behavior our implementation achieves by installing our demo app from TestFlight. The first demo tab has a lot of different streams from several sources (with various encodings and packagings), including the standard Apple test streams. You can also use the demo to compare the behavior we obtain vs. the one provided by the system player UI since we also have included the vanilla system experience in our demo as well (2nd tab).

Oh that’s amazing thanks! Unfortunately your beta isn’t accepting lol but I trust you.

Oh that’s amazing thanks! Unfortunately your beta isn’t accepting lol but I trust you.

Should be fixed now, sorry, there was no recent build enabled for external testing 😇

👍👍