Bug 237799

Created attachment 454520 [details]
WebKit.GPU process logs

I'm not able to resume an HLS stream in mobile Safari after backgrounding the app
Issue is 100% reproducible on Simulator running iOS 13.4 RC. It also reproduces on my iPhone 12 running iOS 13.4 RC

Issue occurred at 15:35:39

Steps to reproduce
- Open https://codepen.io/dgoss/full/eYyOXJX in mobile Safari
- Play 10 seconds of the HLS stream, pause
- Background the app for 10 seconds
- Open mobile Safari, tap Play

WebKit logs that seem relevant

App enters background, WebKit tells MediaPlayer to purge resources
default	15:35:13.302978-0800	71785	com.apple.WebKit.GPU	MediaPlayerPrivateAVFoundationObjC::setBufferingPolicy(4B3AC1364A25C7FC) PurgeResources
default	15:35:13.303014-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfsi_performCurrentResourceConservationAction: [0x125d07280|P/MV] Setting resourceConservationLevelWhenPaused to 3

CoreMedia deletes some tracks
default	15:35:13.306446-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_DeleteTrack: <0x126040a00|I/TKA.01> (0) track 3
default	15:35:13.306461-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_StopFeedingTrack: track 3 stopped feeding without setting EndTimer
default	15:35:13.306510-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_DeleteTrack: <0x126040a00|I/TKA.01> (0) track 5
default	15:35:13.306575-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_StopFeedingTrack: track 5 stopped feeding without setting EndTimer

More purging
default	15:35:16.594082-0800	71785	com.apple.WebKit.GPU	0x104fe3430 - GPUProcess::prepareToSuspend(), isSuspensionImminent: 0
default	15:35:38.120907-0800	71785	com.apple.WebKit.GPU	MediaPlayerPrivateAVFoundationObjC::setBufferingPolicy(4B3AC1364A25C7FC) MakeResourcesPurgeable

App enters foreground and FigStreamPlayer is not ready to play, FigStreamPlayer never recovers
default	15:35:39.340332-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_CheckIfLikelyToKeepUpAndNotify: tried to force playback but NOT ready for playback (0 buffered)
default	15:35:39.340410-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_PostNotificationFromDispatch: posting Remote_RateWillChangeTo on 0x125d07280 (0x6000027d5340)
default	15:35:39.340435-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_PostNotificationFromDispatch: posting RateDidChange on 0x125d07280 (0x6000027d5100)
default	15:35:39.340451-0800	71785	com.apple.WebKit.GPU	<<<< FigStreamPlayer >>>> fpfs_PostNotificationFromDispatch: posting PlaybackStateDidChange on 0x125d07280 (0x6000027d5020)