Why is video playback speed delayed when changing and not instant?

[blonsky95]

Hi there,

I only post this question here because I have had no luck in Stack Overflow and I've read everything I've been able to found in Exoplayer docs.

I'm using the Exoplayer PlaybackParameters in my app to change the speed of the video playback. However the speed change is only carried out a considerable amount of frames later (I guess it waits for closest sync point?).

I am aware that when I set the playback parameters it should trigger default void onPlaybackParametersChanged(PlaybackParameters playbackParameters) so I'm not sure if the delay lies in (setting playbackParameters -> triggering the listener) or in (listener triggered -> applies parameters to playback).

If I make a speed change with the video paused, and seek to a different part of the video, the speed change is carried out immediately, it's only while the playback is running that it carries out the speed change with a delay.

Wondering if there is something like SeekParameters where you can choose to seek to closest Sync point, or ignore sync points at all and use tolerance of 0, so setting the PlaybackParameters don't have to wait to the sync point to change.

I couldn't find anything remotely similar in issues, but please let me know if I am missing something out or any existing solutions to my problem

[Samrobbo]

Hi, could you try calling setEnableAudioTrackPlaybackParams(true) on your DefaultRenderersFactory and see if that makes a difference.

If you don't already have DefaultRenderersFactory, initialize and pass it into the constructor of the builder when creating your SimpleExoPlayer.

Note that this will only work from API 23 onwards.

For pre-API 23, you could look into a smaller AudioTrack buffer, which would be more code than this helper method, and it may increase the chance of an audio underrun.

[blonsky95]

Hi Sam thanks for helping me out,

I just did that and I've been playing around with it for a bit, and it does make it work much quicker, however it doesnt make a smooth transition from the old speed to the new one, and its a bit more clunky:

e.g. if I go speed 1.0 to speed 0.3 in one step, the frames freeze for a second and then start playing at 0.3, and everytime you seek a point in the video (while keeping the playback params speed at 0.3) it does a similar thing, it freezes or starts off at speed 1.0 before adjusting to 0.3

Not sure how helpful that is, but the media audio is quite unsynced (which is not a big issue, just a detail), to the point where when the speed is below 1, e.g. 0.3, the audio goes on after pausing the video. I've tried different frame rates videos and same thing, I might try playing around with LoadControls to change buffering parameters, would it be worth a try?

Without the setEnableAudioTrackPlaybackParams(true) there was a delay but after that, the speed was kept constant, and it didnt feel clunky when seeking throughout video, it was just the delay that was problematic, so something with the best of both of things would be great.

[Samrobbo]

@andrewlewis You worked on the speed adjustment stuff, do you know why that might be happening?

[blonsky95]

I know it's not the best description, but the set up is fairly simple. I'm initialising with just:
val defaultRenderersFactory = DefaultRenderersFactory(this).setEnableAudioTrackPlaybackParams(true)
exoPlayer = SimpleExoPlayer.Builder(this, defaultRenderersFactory).build()

and then setting the playback params (speed 0.2 for example) with:
exoPlayer.setPlaybackParameters(PlaybackParameters(0.2f))

With setEnableAudioTrackPlaybackParams(true) , I get the clunky and inconsistent speed changes, but the almost instant speed change. If I seek to different points in the video while speed is low (e.g. 0.2), some frames freeze for a second, or even accelerate before setting the right speed.

When I initialise exoPlayer without setEnableAudioTrackPlaybackParams(true) I get the playback speed change delay, but consistent new speed after that, I can seek different points and I always see 0.2 speed and no freezing.

Let me know if you need any more info